IS-IS in Junos OS

One of the least popular dynamic routing protocol in the networking works is IS-IS, which stands for Intermediate System to Intermediate System.

I'll be honest, I will not cover everything here, only what I've learned and can do in GNS3. I will make also a video with the configuration in GNS3, just check the bottom of this post for the youtube video link.

Ok, now let's make a simple topology in GNS3 and we will cover with a little bit of theory for each step we will take. And action:

You can also download the image from here.

Now, I won't cover the basic configuration of the devices (IP addresses, router id, ospf, etc), but in the video I will do this for every device.

Ok let's begin with the basic IS-IS configuration in Junos and IOS:

Configuration for Router R1_L1-L2:

rokk@R1_L1-L2> show configuration protocols isis | display set

set protocols isis interface ge-0/0/0.0

set protocols isis interface ge-0/0/1.0

set protocols isis interface ge-0/0/2.0

set protocols isis interface ge-0/0/3.0 passive

As you can see there is not much to it, at least in Junos. The configuration is similar to ospf. The interface ge-0/0/3.0 has a passive there. This means take the route from that interface and advertise to other neighbours, but do not send/receive routing update on this interface. Also similar to ospf.

But that's not all. Actually before the IS-IS configuration is made, some other thins must be done. That is because the IS-IS routing protocols runs over the iso protocol, which is a layer 3 protocol just like IP or IPv6. And we must configure also an iso address for the device to communicate to other devices over IS-IS. The only difference here is that you configure an iso address for the entire device; for IP or IPv6 you have to configure an IP/IPv6 address on every interface.

In Junos, usually the iso address is configured on the loopback interface; It's not a requirement, but this interface won't go down when there is a physical link failure. So how do you configure it and how does it look like. Let's see:

rokk@R1_L1-L2> show configuration interfaces lo0 | display set

set interfaces lo0 unit 0 family inet address 12.12.12.1/32

set interfaces lo0 unit 0 family iso address 49.0021.0000.0000.0121.00

set interfaces lo0 unit 0 family inet6 address fe80::121/64

set interfaces lo0 unit 0 family inet6 address 2001:abc:def:12::1/128

So it looks much different that the IP or IPv6 address (this is one of the reasons this routing protocol is the least popular).

IS-IS routers need a layer 3 address, an iso address, but the address is slightly different than IP or IPv6. In this case the address is called a Network Entity Title (NET), which, again, is one for the entire system (router). The NET is made of 3 parts:

The Area ID
The System ID
The NSEL (NET Selector)

Now let's look at our address and identify the parts:

- 49.0021 <-- is the Area ID

- 0000.0000.0141 <-- is the System ID

- 00 <-- is the NSEL

The Area ID has 2 parts:

AFI = Address Family Identifier. The value of 49 indicates a private use/locally assigned ISO NET.
the area number, which is our case is 00021, or area 21

The System ID is something like OSPF router-id, which identify uniquely the router in the domain. It has to be different for every router in the domain.

The NSEL (the selector field), for a router will always be 00. If the selector filed for a router won't 00 then the adjacency won't be formed.

OK, so now we have the iso address configured on the router, but we also need to enable the protocol iso on every interface which we want to form an adjacency with other routers which are configured for IS-IS. Let's see the configuration for all the interfaces:

rokk@R1_L1-L2> show configuration interfaces

ge-0/0/0 {

    description "Link to SW1 e0/2";

    unit 0 {

        family inet {

            address 10.0.2.3/29;

        family iso;

        family inet6 {

            address 2001:abc:2::3/64;

            address fe80::121/64;

ge-0/0/1 {

    description "Link to R1_L1 ge-0/0/1";

    unit 0 {

        family inet {

            address 10.0.12.1/32;

        family iso;

        family inet6 {

            address fe80::121/64;

            address 2001:abc:12::1/64;

ge-0/0/2 {

    description "Link to R2_L1 ge-0/0/2";

    unit 0 {

        family inet {

            address 10.0.12.5/30;

        family iso;

        family inet6 {

            address fe80::121/64;

            address 2001:abc:12:4::5/64;

ge-0/0/3 {

    description "Link to R1-E e0/0";

    unit 0 {

        family inet {

            address 192.168.1.1/30;

        family inet6 {

            address fe80::121/64;

            address 2001:abc:192::1/64;

lo0 {

    unit 0 {

        family inet {

            address 12.12.12.1/32;

        family iso {

            address 49.0021.0000.0000.0121.00;

        family inet6 {

            address fe80::121/64;

            address 2001:abc:def:12::1/128;

And now the IS-IS protocol configuration:

rokk@R2_L1-L2> show configuration protocols isis | display set

set protocols isis interface ge-0/0/0.0

set protocols isis interface ge-0/0/1.0

set protocols isis interface ge-0/0/2.0

On interface ge-0/0/3 the protocol iso is not configured. We don't need it here, because here we will enable OSPF withe the external router R1-E and advertise the routing information from OSPF into IS-IS.

And, the cool part about IS-IS is that it will carry both IP and IPv6 addresses in a singe configuration. If you remember that for OSPF we have to configure a different protocol for IPv6 (ospfv3), but not here for IS-IS. This is because IS-IS routing protocol was created for the ISO protocol, which is now only a reference model (ISO Model) and describes how data is flowing trough the network. But the actual protocol that rules the world today is TCP/IP. And since IS-IS was created for the ISO protocol, it was modified for TCP/IP and is called now Integrated IS-IS (this is actually configured now). Even though IS-IS was not initially designed for IP, it provides a simple way to add new extensions by using TLV (Type Length Value) fields. The concept is: Just adding new TLVs for a new protocol family and If you don’t support a given TLV just silently ignore it. More on this later.

Now let's see the configuration for router R2_L1-L2:

the interface configuration:

interfaces {

    ge-0/0/0 {

        description "Link to SW1 e0/3";

        unit 0 {

            family inet {

                address 10.0.2.4/29;

            family iso;

            family inet6 {

                address fe80::122/64;

                address 2001:abc:2::4/64;

    ge-0/0/1 {

        description "Link to R2_L1 ge-0/0/1";

        unit 0 {

            family inet {

                address 10.0.12.13/30;

            family iso;

            family inet6 {

                address fe80::122/64;

                address 2001:abc:12:12::13/64;

    ge-0/0/2 {

        description "Link to R1_L1 ge-0/0/2";

        unit 0 {

            family inet {

                address 10.0.12.9/30;

            family iso;

            family inet6 {

                address fe80::122/64;

                address 2001:abc:12:8::9/64;

    lo0 {

        unit 0 {

            family inet {

                address 12.12.12.2/32;

            family iso {

                address 49.0021.0000.0000.0122.00;

            family inet6 {

                address fe80::122/64;

                address 2001:abc:def:12::2/128;

You will see here that the iso protocol is enabled for all the interfaces (I hope you did download the image to have the map for a clear understanding), this is because we want to establish a neighbour adjacency on every interface.

I hope you also observed that the iso address configured on the loopback 0 has the same area ID: 49.0021.0000.0000.0122.00.

This is because the adjacency will form on the circuit (which is the link between two or more nodes), and there are some rules here as follow:

A Level 1 adjacency will form on a circuit only if the routers are in the same area; and here the two routers (R1_L1-L2 and R2_L1_L2) are in the same area because they will form an adjacency with routers R1_L1 and R2_L1.
A Level 2 adjacency will form on a circuit even if the routers are not in the same area. They can be in the same area, but is not mandatory. This is done for scalability of the network.
A Level 1 configured of one side of the link and a Level 2 configured for the other end will not form an adjacency.

So this will work:

L1 <--> L1
L2 <--> L2
L1/L2 <--> L1/L2

But this will NOT work:

L1 <--> L2
L2 <--> L1

Ok, now, but have do we do this, I mean on the config above there is nothing that says that the link is a Level 1 circuit or a Level 2 circuit?

Well, this is because in Junos if you don't specify, the router will try to form an L1/L2 <--> L1/L2 adjacency. OK, now before we check the adjacency between R1_L1-L2 and R2_L1-L2 let's create a traceoption file (debug) for to see the process, to see how the adjacency comes up. Let's do this only on router R1_L1-L2. And here is the config for this:

protocols {

    isis {

        traceoptions {

            file IS-IS-adj size 10k files 2 world-readable;

            flag state detail;

IS-IS-adj is the name of the file, the size is set to minimum 10k and the the number of files is set also to minimum which is 2. And the flag specify which debug messages we wand to see. Now from operation mode we will start the monitor of the file wit the command:

rokk@R1_L1-L2> monitor start IS-IS-adj

Now let's see the output of the 2 routers (R1_L1-L2 and R2_L1-L2) forming an adjacency:

*** IS-IS-adj ***

Jun  1 08:20:25.656811 New adjacency for 0000.0000.0122 on ge-0/0/0.0, level 1

Jun  1 08:20:25.660495 Adjacency state change, 0000.0000.0122, state New -> Initializing

Jun  1 08:20:25.660509     interface ge-0/0/0.0, level 1

Jun  1 08:20:25.660937 ISIS L1 neighbor 0000.0000.0122 on interface ge-0/0/0.0 set 27 secs 0 nsecs

Jun  1 08:20:25.675893 Adjacency state change, 0000.0000.0122, state Initializing -> Up

Jun  1 08:20:25.675904     interface ge-0/0/0.0, level 1

Jun  1 08:20:25.682056 New adjacency for 0000.0000.0122 on ge-0/0/0.0, level 2

Jun  1 08:20:25.682082 Adjacency state change, 0000.0000.0122, state New -> Initializing

Jun  1 08:20:25.682087     interface ge-0/0/0.0, level 2

Jun  1 08:20:25.682145 Adjacency state change, 0000.0000.0122, state Initializing -> Up

Jun  1 08:20:25.682150     interface ge-0/0/0.0, level 2

As we can see here, there where 2 adjacency established between the two routers (R1_L1-L2 and R2_L1-L2), one Level 1 adjacency and one Level 2 adjacency. Now let's see the output of the show isis adjacency:

rokk@R1_L1-L2> show isis adjacency

Interface             System         L State        Hold (secs) SNPA

ge-0/0/0.0            R2_L1-L2       1  Up                    6  0:5:86:71:ae:0

ge-0/0/0.0            R2_L1-L2       2  Up                    7  0:5:86:71:ae:0

It shows the interface on which the neighbour was learned. Then the system, which is the router hostname of the neighbour. And then which kind of adjacency was created; as we can see there is L1 and L2 adjacency. The last one is the SPNA (subnetwork point of attachment) which is actually the mac address of the router interface. This is the output of from R1_L1-L2, this means that the SPNA address here is the mac address of the neighbour router with which was formed an adjacency. Let's see the mac address of the other router:

rokk@R2_L1-L2> show interfaces ge-0/0/0 | match "Hardware address"

  Current address: 00:05:86:71:ae:00, Hardware address: 00:05:86:71:ae:00

Yes, looks good. Now let's look at the detail output to see more info:

rokk@R1_L1-L2> show isis adjacency detail

R2_L1-L2

  Interface: ge-0/0/0.0, Level: 1, State: Up, Expires in 7 secs

  Priority: 64, Up/Down transitions: 1, Last transition: 00:36:11 ago

  Circuit type: 3, Speaks: IP, IPv6, MAC address: 0:5:86:71:ae:0

  Topologies: Unicast

  Restart capable: Yes, Adjacency advertisement: Advertise

  LAN id: R2_L1-L2.02, IP addresses: 10.0.2.4

  IPv6 addresses: fe80::122

R2_L1-L2

  Interface: ge-0/0/0.0, Level: 2, State: Up, Expires in 6 secs

  Priority: 64, Up/Down transitions: 1, Last transition: 00:36:11 ago

  Circuit type: 3, Speaks: IP, IPv6, MAC address: 0:5:86:71:ae:0

  Topologies: Unicast

  Restart capable: Yes, Adjacency advertisement: Advertise

  LAN id: R2_L1-L2.02, IP addresses: 10.0.2.4

  IPv6 addresses: fe80::122

Like we said before: we have configured a single routing protocol which supports more that one Layer 3 protocol (Speaks: IP, IPv6). The Circuit type is 3. Why 3? well it's a fixed value. It can be 0, 1, 2 and 3. The rules are:

Type 3 means: an L1/L2 adjacency is on the circuit;
Type 2 means: an L2 adjacency is on the circuit (remember, circuit means the link between the routers);
Type 1 means: an L1 adjacency is on the circuit;
Type 0 means: no adjacency will be formed on the link because the protocol iso is not enabled on the interface.

Ok, now let's look at the interfaces on which the IS-IS was enabled for both of the routers to see if there are some differences:

rokk@R1_L1-L2> show isis interface detail | no-more

IS-IS interface database:

ge-0/0/0.0

  Index: 330, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             1       64     10     9.000       27 R2_L1-L2.02 (not us)

    2             1       64     10     9.000       27 R2_L1-L2.02 (not us)

ge-0/0/1.0

  Index: 331, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10     9.000       27

    2             0       64     10     9.000       27

ge-0/0/2.0

  Index: 332, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10     9.000       27

    2             0       64     10     9.000       27

ge-0/0/3.0

  Index: 333, State: 0x4, Circuit id: 0x1, Circuit type: 0

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10 Passive

    2             0       64     10 Passive

Right now an adjacency has formed only on interface ge-0/0/0.0. We see that there are actually 2 adjacency on the same interface, the circuit type is 3, because is a L1/L2 adjacency (but we will change that later), and there is more. You will see Hello time in seconds, Hold time in seconds and Designated Router, just like in OSPF. But look at below at the output of router R2_L1-L2, the Hello time and Hold time is different, but why? Let's first talk about the Designated router first.

rokk@R2_L1-L2> show isis interface detail | no-more

IS-IS interface database:

ge-0/0/0.0

  Index: 329, State: 0x6, Circuit id: 0x2, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             1       64     10     3.000        9 R2_L1-L2.02 (us)

    2             1       64     10     3.000        9 R2_L1-L2.02 (us)

ge-0/0/1.0

  Index: 330, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10     9.000       27

    2             0       64     10     9.000       27

ge-0/0/2.0

  Index: 331, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10     9.000       27

    2             0       64     10     9.000       27

IS-IS is like OSPF a link state dynamic routing protocols and elects a Designated router in a broadcast or multi-access network. But there are some differences:

In IS-IS the designated router is called the designated intermediate system, (DIS - but IS means router, so you can translate it also as designated router).

The IS-IS DIS election process is achieved by assigning a priority for Level 1 and Level 2 on every interface where IS-IS was enabled. The priority is a number from 0 to 127. The Junos OS uses a default priority of 64 for both levels. If the priority is 0 on an interface then the router will never be the DIS on the segment (just like in OSPF), and of course, the higher the priority, the better. The router with the highest priority on the interface wins the election process. But, by default is 64 and if you don't change this, by configure it to some other value, then the tie breaker becomes the the mac address of links (SPNA - subnetwork point of attachment). And then the router with the highest numerically mac address wins the election process. So let's see in our example:

R1_L1-L2 has a priority of 64 (default one) and the mac address of the interface is:

rokk@R1_L1-L2> show interfaces ge-0/0/0 | match "Hardware address"

  Current address: 00:05:86:71:67:00, Hardware address: 00:05:86:71:67:00

R2_L1-L2 has a priority of 64 and the mac address of the interface is:

rokk@R2_L1-L2> show interfaces ge-0/0/0 | match "Hardware address"

  Current address: 00:05:86:71:ae:00, Hardware address: 00:05:86:71:ae:00

And the winner is R2_L1-L2, because has the highest mac address on the link, for both Level 1 and Level 2. Let's see again the output:

rokk@R2_L1-L2> show isis interface ge-0/0/0.0 detail

IS-IS interface database:

ge-0/0/0.0

  Index: 329, State: 0x6, Circuit id: 0x2, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             1       64     10     3.000        9 R2_L1-L2.02 (us)

    2             1       64     10     3.000        9 R2_L1-L2.02 (us)

------------------------------------------------------------------------------------------------------

rokk@R1_L1-L2> show isis interface ge-0/0/0.0 detail

IS-IS interface database:

ge-0/0/0.0

  Index: 330, State: 0x6, Circuit id: 0x1, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             1       64     10     9.000       27 R2_L1-L2.02 (not us)

    2             1       64     10     9.000       27 R2_L1-L2.02 (not us)

Now the Hello and Hold interval time in seconds. Here are the rules (the default ones):

By default, a designated intersystem (DIS) router sends hello packets every 3 seconds, and a non-DIS router sends hello packets every 9 seconds.
The default hold-time value is three times the default hello interval: 9 seconds for a DIS router and 27 seconds for a non-DIS router.

I think there is enough about the theory, for more of this I will put at the bottom the resources I used for this post. But for now let's put some objectives for the topology:

Configure IS-IS on the cisco routers and see if the DIS is changing or not. Then change the priority to a higher number of a router and to 0 for another router to see the changes.
Configure router R1-L2 and R2_L2 as only a Level 2 routers. Also the interface ge-0/0/0 for routers R1_L1-L2 and R2_L1-L2 should be configured only as Level 2. The remaining interfaces of routers R1_L1-L2 and R2_L1-L2 should be configured as Level 1 circuits.
On router R1_L1-L2 interface ge-0/0/3 should be remain as passive. The same for the interface ge-0/0/3 on router R2_L1.
Configured R1_L1 and R2_L1 as only Level 1 routers in the same area 21.
Configured OSPF between R1_L1-L2 and the external router R1-E in area 0.
Configured OSPF between R2_L1 and the external router R2-E in area 0.
Advertise the routes learned trough OSPF into IS-IS on both routers R1_L1-L2 and R2_L1.
Change the default metric and the reference bandwidth for both IS-IS and OSPF.
I think that's it for now. I will add more objective in the video, just for fun.

Configuration for R1_L2:

router isis

 net 49.0002.0000.0000.0021.00

 is-type level-2-only

 router-id Loopback0

nterface Loopback0

 ip address 2.2.2.1 255.255.255.255

 ip router isis

 ipv6 address FE80::21 link-local

 ipv6 address 2001:ABC:DEF:2::1/128

 ipv6 router isis

interface Ethernet0/0

 description Link to SW1 e0/0

 ip address 10.0.2.1 255.255.255.248

 ip router isis

 duplex auto

 ipv6 address FE80::21 link-local

 ipv6 address 2001:ABC:2::1/64

 ipv6 router isis

interface Serial1/0

 description Link to R2_L2 s1/0

 ip address 10.0.2.9 255.255.255.252

 ip router isis

 ipv6 address FE80::21 link-local

 ipv6 address 2001:ABC:2:8::9/64

 ipv6 router isis

 serial restart-delay 0

Configuration for R2_L2:

router isis

 net 49.0002.0000.0000.0022.00

 is-type level-2-only

 router-id Loopback0

interface Loopback0

 ip address 2.2.2.2 255.255.255.255

 ip router isis

 ipv6 address FE80::22 link-local

 ipv6 address 2001:ABC:DEF:2::2/128

 ipv6 router isis

interface Ethernet0/0

 description Link to SW1 e0/1

 ip address 10.0.2.2 255.255.255.248

 ip router isis

 duplex auto

 ipv6 address FE80::22 link-local

 ipv6 address 2001:ABC:2::2/64

 ipv6 router isis

interface Serial1/0

 description Link to R1 s1/0

 ip address 10.0.2.10 255.255.255.252

 ip router isis

 ipv6 address FE80::22 link-local

 ipv6 address 2001:ABC:2:8::10/64

 ipv6 router isis

 serial restart-delay 0

The two routers where configured only for Level 2. Now we will see on router R1_L1-L2 if the DIS router was changed:

rokk@R1_L1-L2> show isis interface detail

IS-IS interface database:

ge-0/0/0.0

  Index: 330, State: 0x6, Circuit id: 0x2, Circuit type: 3

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             1       64     10     3.000        9 R1_L1-L2.02 (us)

    2             3       64     10     9.000       27 R2_L2.01 (not us)

From the output we can see that there are e adjacency for Level 2:

rokk@R1_L1-L2> show isis adjacency

Interface             System         L State        Hold (secs) SNPA

ge-0/0/0.0            R1_L2          2  Up                   22  aa:bb:cc:0:1:0

ge-0/0/0.0            R2_L2          2  Up                    8  aa:bb:cc:0:4:0

ge-0/0/0.0            R2_L1-L2       1  Up                   26  0:5:86:71:3b:0

ge-0/0/0.0            R2_L1-L2       2  Up                   19  0:5:86:71:3b:0

So, one adjacency with router R1_L2, one with R2_L2 and one with R2_L1-L2. And only one Level 1 adjacency with router R2_L1-L2.

We also noticed that the DIS router was changed for the Level 2 adjacency, but why? Let's remember. The higher the priority the better. But by default the priority is 64. So the next one is the mac address. Let's see the mac address of the four routers:

rokk@R1_L1-L2> show interfaces ge-0/0/0 | match "Hardware address"

  Current address: 00:05:86:71:42:00, Hardware address: 00:05:86:71:42:00

--------------------------------------------------------------------------

rokk@R2_L1-L2> show interfaces ge-0/0/0 | match "Hardware address"

  Current address: 00:05:86:71:3b:00, Hardware address: 00:05:86:71:3b:00

--------------------------------------------------------------------------

R1_L2#show interfaces ethernet 0/0 | include Hardware

  Hardware is AmdP2, address is aabb.cc00.0100 (bia aabb.cc00.0100)

--------------------------------------------------------------------------

R2_L2#show interfaces ethernet 0/0 | include Hardware

  Hardware is AmdP2, address is aabb.cc00.0400 (bia aabb.cc00.0400)

So, router R2_L2 is the winner!!. Ok, but wait. Router R2_L1-L2 was already the DIS router, is this here some kind of preemption? Yes, exactly like you enable preemption for HSRP, or VRRP. Here, in the DIS election, if there is another router in the LAN segment with a higher priority/mac address, then the router takes the role as DIS router.

Great until now. Let's change the priority for router R1_L1-L2 to 100 and for router R2_L2 to 0. And here is how we do that:

rokk@R1_L1-L2> show configuration protocols isis | display set

set protocols isis interface ge-0/0/0.0 level 2 priority 100

set protocols isis interface ge-0/0/0.0 level 1 disable

set protocols isis interface ge-0/0/1.0 level 2 disable

set protocols isis interface ge-0/0/2.0 level 2 disable

set protocols isis interface ge-0/0/3.0 passive

--------------------------------------------------------------

R2_L2#show running-config interface ethernet 0/0

interface Ethernet0/0

 description Link to SW1 e0/1

 ip address 10.0.2.2 255.255.255.248

 ip router isis

 duplex auto

 ipv6 address FE80::22 link-local

 ipv6 address 2001:ABC:2::2/64

 ipv6 router isis

 isis priority 0

For Junos OS the configuration is done under the protocol isis and for IOS the configuration is done under the interface. You also notice that for R1_L1-L2 there are some level 2 passive and level 1 passive statements there. This was done so that for the DIS should be elected only for level 2 between R1_L1-L2 and R2_L1-L2 (it is also the second objective).

Now let's see who wins the election:

rokk@R1_L1-L2> show isis interface ge-0/0/0.0 detail

IS-IS interface database:

ge-0/0/0.0

  Index: 330, State: 0x6, Circuit id: 0x2, Circuit type: 2

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10 Disabled

    2             3      100     10     3.000        9 R1_L1-L2.02 (us)

Perfect. Preemption was taken effect and now router R1_L1-L2 is the DIS router. Great, point 1 and 2 done.

The objective for point 3 was: "On router R1_L1-L2 interface ge-0/0/3 should be remain as passive. The same for the interface ge-0/0/3 on router R2_L1".

Now for the router R1_L1-L2 the interface ge-0/0/3 is already as passive, so only router R2_L1 remains to configure:

set protocols isis interface ge-0/0/0.0 point-to-point

set protocols isis interface ge-0/0/0.0 level 2 disable

set protocols isis interface ge-0/0/1.0 point-to-point

set protocols isis interface ge-0/0/1.0 level 2 disable

set protocols isis interface ge-0/0/2.0 point-to-point

set protocols isis interface ge-0/0/2.0 level 2 disable

set protocols isis interface ge-0/0/3.0 passive

So, this is it, not much to do. Also, the point to point was configured between this router and the other that participate in the IS-IS adjacency. This is to disable the election for a DIS. To mention here is that, you have to configure both sides as point-to-point to make the adjacency work. Otherwise, no adjacency will be formed.

rokk@R2_L1> show isis interface ge-0/0/0.0 detail

IS-IS interface database:

ge-0/0/0.0

  Index: 329, State: 0x6, Circuit id: 0x1, Circuit type: 1

  LSP interval: 100 ms, CSNP interval: disabled

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10     9.000       27

    2             0       64     10 Disabled

rokk@R2_L1> show isis interface ge-0/0/3.0 detail

IS-IS interface database:

ge-0/0/3.0

  Index: 332, State: 0x4, Circuit id: 0x1, Circuit type: 0

  LSP interval: 100 ms, CSNP interval: 10 s

  Adjacency advertisement: Advertise

  Level Adjacencies Priority Metric Hello (s) Hold (s) Designated Router

    1             0       64     10 Passive

    2             0       64     10 Passive

So, for this router R2_L1, there is not a DIS election. And is enabled only for Level 1, as you can see the Hello timer for Level 2 is disabled.

Also for interface ge-0/0/3.0 is configured as passive, so no adjacency will be formed trough this interface. So objective 3 done.

Objective 4 is: Configured R1_L1 and R2_L1 as only Level 1 routers in the same area 21.

Configuration for R1_L1:

interfaces {

    ge-0/0/0 {

        description "Link to R2_L1 ge-0/0/0";

        unit 0 {

            family inet {

                address 10.0.1.1/30;

            family iso;

            family inet6 {

                address fe80::11/64;

                address 2001:abc:1::1/64;

    ge-0/0/1 {

        description "Link to R1_L1-L2 ge-0/0/1";

        unit 0 {

            family inet {

                address 10.0.12.2/30;

            family iso;

            family inet6 {

                address fe80::11/64;

                address 2001:abc:12::1/64;

    ge-0/0/2 {

        description "Link to R2_L1-L2 ge-0/0/2";

        unit 0 {

            family inet {

                address 10.0.12.10/30;

            family iso;

            family inet6 {

                address fe80::11/64;

                address 2001:abc:12:8::10/64;

    lo0 {

        unit 0 {

            family inet {

                address 1.1.1.1/32;

            family iso {

                address 49.0021.0000.0000.0011.00;

            family inet6 {

                address fe80::11/64;

                address 2001:abc:def:1::1/128;

protocols {

    isis {

        interface ge-0/0/0.0 {

            point-to-point;

            level 2 disable;

        interface ge-0/0/1.0 {

            point-to-point;

            level 2 disable;

        interface ge-0/0/2.0 {

            point-to-point;

            level 2 disable;

Configuration for R2-L1:

interfaces {

    ge-0/0/0 {

        description "Link to R1_L1 ge-0/0/0";

        unit 0 {

            family inet {

                address 10.0.1.2/30;

            family iso;

            family inet6 {

                address fe80::12/64;

                address 2001:abc:1::2/64;

    ge-0/0/1 {

        description "Link to R2_L1-L2 ge-0/0/1";

        unit 0 {

            family inet {

                address 10.0.12.14/30;

            family iso;

            family inet6 {

                address 2001:abc:12:12::14/64;

                address fe80::12/64;

    ge-0/0/2 {

        description "Link to R1_L1-L2 ge-0/0/1";

        unit 0 {

            family inet {

                address 10.0.12.6/30;

            family iso;

            family inet6 {

                address fe80::12/64;

                address 2001:abc:12:4::6/64;

    ge-0/0/3 {

        description "Link to R2-E e0/0";

        unit 0 {

            family inet {

                address 172.16.1.1/30;

            family inet6 {

                address fe80::12/64;

                address 2001:abc:172::1/64;

    lo0 {

        unit 0 {

            family inet {

                address 1.1.1.2/32;

            family iso {

                address 49.0021.0000.0000.0012.00;

            family inet6 {

                address 2001:abc:def:1::2/128;

protocols {

    isis {

        interface ge-0/0/0.0 {

            point-to-point;

            level 2 disable;

        interface ge-0/0/1.0 {

            point-to-point;

            level 2 disable;

        interface ge-0/0/2.0 {

            point-to-point;

            level 2 disable;

        interface ge-0/0/3.0 {

            passive;

I hope you have download the topology, to have a better look.

Now let's see the neighbours from R1_L1 perspective:

rokk@R1_L1> show isis adjacency

Interface             System         L State        Hold (secs) SNPA

ge-0/0/0.0            R2_L1          1  Up                   22

ge-0/0/1.0            R1_L1-L2       1  Up                   23

ge-0/0/2.0            R2_L1-L2       1  Up                   19

Looks good.

Interesting here is that, a Level 1 router knows only the routes from a Level 1 domain. So only the routes in his area and only the level 1 routes. But there is more. To reach a destination from outside his area, the Level 1 router generates himself a default route that is pointing to the nearest Level 2 router, because that how he know how to get outside of his area. The interesting part is that this does the Level 1 router. It's not like OSPF, the ABR generate a default route for a totally stubby area. Here the Level 1 router does that, and by default and you don't have to configure something specific for that. Let's see the routing table for IS-IS from R1_L1:

rokk@R1_L1> show route table inet.0 protocol isis

inet.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[IS-IS/15] 00:14:05, metric 10

                      to 10.0.12.1 via ge-0/0/1.0

                    > to 10.0.12.9 via ge-0/0/2.0

10.0.12.4/30       *[IS-IS/15] 00:14:05, metric 20

                    > to 10.0.1.2 via ge-0/0/0.0

                      to 10.0.12.1 via ge-0/0/1.0

10.0.12.12/30      *[IS-IS/15] 00:22:31, metric 20

                    > to 10.0.1.2 via ge-0/0/0.0

                      to 10.0.12.9 via ge-0/0/2.0

172.16.1.0/30      *[IS-IS/15] 00:23:03, metric 20

                    > to 10.0.1.2 via ge-0/0/0.0

192.168.1.0/30     *[IS-IS/15] 00:14:05, metric 20

                    > to 10.0.12.1 via ge-0/0/1.0

If you can see from the routing table the default route has 2 next-hop. It seems like there is a load balancing path but, on Junos OS, you have to configure a policy for load balancing (and only equal cost load balancing). Now let's take a closer look only at the default route that was generated:

rokk@R1_L1> show route 0.0.0.0 extensive

inet.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)

0.0.0.0/0 (1 entry, 1 announced)

TSI:

KRT in-kernel 0.0.0.0/0 -> {10.0.12.9}

        *IS-IS  Preference: 15

                Level: 1

                Next hop type: Router

                Address: 0x95a4200

                Next-hop reference count: 1

                Next hop: 10.0.12.1 via ge-0/0/1.0

                Session Id: 0x0

                Next hop: 10.0.12.9 via ge-0/0/2.0, selected

                Session Id: 0x0

                State: <Active Int>

                Age: 14:41      Metric: 10

                Validation State: unverified

                Task: IS-IS

                Announcement bits (1): 0-KRT

                AS path: I

From here we see that it is a Level 1 route, and that actually the next hop is 10.0.12.9, which is router R2_L1-L2, you can see from:

KRT in-kernel 0.0.0.0/0 -> {10.0.12.9}

or:

Next hop: 10.0.12.9 via ge-0/0/2.0, selected

The metric is 10 and the route is learned trough IS-IS protocol, with a route preference of 15 (aka administrative distance).

If we are here, let's talk more about the route preference and the metric of this routing protocol.

By default:

Level 1 IS-IS internal routes have a preference value of 15
Level 2 IS-IS internal routes have a preference of 18
Level 1 IS-IS external routes have a preference of 160
Level 2 IS-IS external routes have a preference of 165

Objective number 5 is: Configured OSPF between R1_L1-L2 and the external router R1-E in area 0.

Ok, but here we will configure ospf and ospfv3 (for IPv6). This topic is about IS-IS, so here I will paste only the configuration for OSPF for both of the routers.

Configuration for router R1_L1-L2:

set protocols ospf area 0.0.0.0 interface ge-0/0/3.0

set protocols ospf3 area 0.0.0.0 interface ge-0/0/3.0

Yes, I know. Not much.

Configuration for router R1-E:

router ospf 1

 router-id 1.1.1.1

 passive-interface default

 no passive-interface Ethernet0/0

ipv6 router ospf 1

 router-id 1.1.1.1

 passive-interface default

 no passive-interface Ethernet0/0

interface Loopback2

 ip address 192.168.2.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::1 link-local

 ipv6 address 2001:192:2::1/64

 ipv6 ospf 1 area 0

interface Loopback3

 ip address 192.168.3.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::1 link-local

 ipv6 address 2001:192:3::1/64

 ipv6 ospf 1 area 0

interface Loopback4

 ip address 192.168.4.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::1 link-local

 ipv6 address 2001:192:4::1/64

 ipv6 ospf 1 area 0

interface Ethernet0/0

 description Link to R1_L1-L2 ge-0/0/3

 ip address 192.168.1.2 255.255.255.252

 ip ospf 1 area 0

 ipv6 address FE80::1 link-local

 ipv6 address 2001:ABC:192::2/64

 ipv6 ospf 1 area 0

And the adjacency should be up, let's check:

rokk@R1_L1-L2> show ospf neighbor

Address          Interface              State     ID               Pri  Dead

192.168.1.2      ge-0/0/3.0             Full      1.1.1.1            1    31

rokk@R1_L1-L2> show ospf3 neighbor

ID               Interface              State     Pri   Dead

1.1.1.1          ge-0/0/3.0             Full        1     37

  Neighbor-address fe80::1

And the routing table of router R1_L1-L2:

rokk@R1_L1-L2> show route protocol ospf

inet.0: 20 destinations, 20 routes (20 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

192.168.2.1/32     *[OSPF/10] 00:15:51, metric 2

                    > to 192.168.1.2 via ge-0/0/3.0

192.168.3.1/32     *[OSPF/10] 00:15:51, metric 2

                    > to 192.168.1.2 via ge-0/0/3.0

192.168.4.1/32     *[OSPF/10] 00:15:51, metric 2

                    > to 192.168.1.2 via ge-0/0/3.0

224.0.0.5/32       *[OSPF/10] 00:16:06, metric 1

                      MultiRecv

inet6.0: 21 destinations, 25 routes (21 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

2001:192:2::1/128  *[OSPF3/10] 00:14:38, metric 1

                    > to fe80::1 via ge-0/0/3.0

2001:192:3::1/128  *[OSPF3/10] 00:14:38, metric 1

                    > to fe80::1 via ge-0/0/3.0

2001:192:4::1/128  *[OSPF3/10] 00:14:38, metric 1

                    > to fe80::1 via ge-0/0/3.0

ff02::5/128        *[OSPF3/10] 00:14:43, metric 1

                      MultiRecv

Looks good until now. And I think we can do objective number 6 here also.

Let's see the configuration of router R2_L1:

set protocols ospf area 0.0.0.0 interface ge-0/0/3.0

set protocols ospf3 area 0.0.0.0 interface ge-0/0/3.0

And the configuration of router R2-E:

router ospf 1

 router-id 2.2.2.2

 passive-interface default

 no passive-interface Ethernet0/0

ipv6 router ospf 1

 router-id 2.2.2.2

 passive-interface default

 no passive-interface Ethernet0/0

interface Loopback2

 ip address 172.16.2.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::2 link-local

 ipv6 address 2001:172:2::1/64

 ipv6 ospf 1 area 0

interface Loopback3

 ip address 172.16.3.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::2 link-local

 ipv6 address 2001:172:3::1/64

 ipv6 ospf 1 area 0

interface Loopback4

 ip address 172.16.4.1 255.255.255.0

 ip ospf 1 area 0

 ipv6 address FE80::2 link-local

 ipv6 address 2001:172:4::1/64

 ipv6 ospf 1 area 0

interface Ethernet0/0

 ip address 172.16.1.2 255.255.255.252

 ip ospf 1 area 0

 ipv6 address FE80::2 link-local

 ipv6 address 2001:ABC:172::2/64

 ipv6 ospf 1 area 0

And let's check the neighbour adjacency:

rokk@R2_L1> show ospf neighbor

Address          Interface              State     ID               Pri  Dead

172.16.1.2       ge-0/0/3.0             Full      2.2.2.2            1    36

rokk@R2_L1> show ospf3 neighbor

ID               Interface              State     Pri   Dead

2.2.2.2          ge-0/0/3.0             Full        1     32

  Neighbor-address fe80::2

Now, on router R2_L1 there should be some routes learned from router R2-E. Let's see:

rokk@R2_L1> show route protocol ospf

inet.0: 17 destinations, 17 routes (17 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

172.16.2.1/32      *[OSPF/10] 00:04:34, metric 2

                    > to 172.16.1.2 via ge-0/0/3.0

172.16.3.1/32      *[OSPF/10] 00:04:34, metric 2

                    > to 172.16.1.2 via ge-0/0/3.0

172.16.4.1/32      *[OSPF/10] 00:04:34, metric 2

                    > to 172.16.1.2 via ge-0/0/3.0

224.0.0.5/32       *[OSPF/10] 00:04:49, metric 1

                      MultiRecv

inet6.0: 20 destinations, 23 routes (20 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

2001:172:2::1/128  *[OSPF3/10] 00:04:44, metric 1

                    > to fe80::2 via ge-0/0/3.0

2001:172:3::1/128  *[OSPF3/10] 00:04:44, metric 1

                    > to fe80::2 via ge-0/0/3.0

2001:172:4::1/128  *[OSPF3/10] 00:04:44, metric 1

                    > to fe80::2 via ge-0/0/3.0

ff02::5/128        *[OSPF3/10] 00:04:49, metric 1

                      MultiRecv

And... that's it. Now the good part. Objective number 7 was: Advertise the routes learned trough OSPF into IS-IS on both routers R1_L1-L2 and R2_L1. And we begin on router R2_L1. Here is the configuration:

rokk@R2_L1> show configuration policy-options

policy-statement OSPF {

    term 1 {

        from {

            protocol ospf;

            route-filter 172.16.2.1/32 exact;

            route-filter 172.16.3.1/32 exact;

            route-filter 172.16.4.1/32 exact;

        then accept;

    term 2 {

        from {

            protocol ospf3;

            route-filter 2001:172:2::1/128 exact;

            route-filter 2001:172:3::1/128 exact;

            route-filter 2001:172:4::1/128 exact;

        then accept;

rokk@R2_L1> show configuration protocols isis

export OSPF;

Redistribution from OSPF to IS-IS in Junos is done trough a policy. This is done under policy-options policy-statement hierarchy. The name of the policy is OSPF and it has 2 terms. The first one is for ospf for IPv4 and the second one is for ospfv3 for IPv6. And it says, take the exact routes from the routing table which was learned trough protocol ospf and ospfv3 and accept them.

The policy is just to match the traffic (you can also modify some parameters), but that's it. I mean, the policy take effect after it's applied to the routing protocol IS-IS. OK. Now let's see the results from a Level 1 router and a Level 2 router. R1_L1-L2 and R1_L1:

rokk@R1_L1-L2> show route 172.16.2.1

inet.0: 23 destinations, 23 routes (23 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

172.16.2.1/32      *[IS-IS/160] 01:06:21, metric 12

                    > to 10.0.12.6 via ge-0/0/2.0

---------------------------------------------------------------------

rokk@R1_L1-L2> show route 172.16.2.1 extensive

inet.0: 23 destinations, 23 routes (23 active, 0 holddown, 0 hidden)

172.16.2.1/32 (1 entry, 1 announced)

TSI:

KRT in-kernel 172.16.2.1/32 -> {10.0.12.6}

        *IS-IS  Preference: 160

                Level: 1

                Next hop type: Router, Next hop index: 612

                Address: 0x9764f28

                Next-hop reference count: 10

                Next hop: 10.0.12.6 via ge-0/0/2.0, selected

                Session Id: 0x9

                State: <Active Int Ext>

                Age: 1:06:27    Metric: 12

                Validation State: unverified

                Task: IS-IS

                Announcement bits (1): 0-KRT

                AS path: I

So, router R1_L1-L2 is receiving the route from router with the IP 10.0.12.6 (which is router R2_L1) as a Level 1 route, but as a Level 1 external route. We can see this because the route preference is 160. The route preference of 165 is for a Level 2 route. So we can conclude from here that a Level 1 route is more preferred than a Level 2 route. The same is for internal routes.

Now let's see the routing table for IPv6. The route preference should be the same here:

rokk@R1_L1-L2> show route 2001:172:3::1

inet6.0: 25 destinations, 29 routes (25 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

2001:172:3::1/128  *[IS-IS/160] 01:15:56, metric 11

                    > to fe80::12 via ge-0/0/2.0

------------------------------------------------------------------------

rokk@R1_L1-L2> show route 2001:172:3::1 extensive

inet6.0: 25 destinations, 29 routes (25 active, 0 holddown, 0 hidden)

2001:172:3::1/128 (1 entry, 1 announced)

TSI:

KRT in-kernel 2001:172:3::1/128 -> {fe80::12}

        *IS-IS  Preference: 160

                Level: 1

                Next hop type: Router, Next hop index: 613

                Address: 0x9764f7c

                Next-hop reference count: 11

                Next hop: fe80::12 via ge-0/0/2.0, selected

                Session Id: 0xa

                State: <Active Int Ext>

                Age: 1:15:59    Metric: 11

                Validation State: unverified

                Task: IS-IS

                Announcement bits (1): 0-KRT

                AS path: I

As we can see, the same here. The only difference here is that the next hope for this route is the link local address of the neighbour router.

Good, looks nice. Let's see now the same, but from the perspective of a Level 1 router, R1_L1:

rokk@R1_L1> show route 172.16.4.1 extensive

inet.0: 15 destinations, 15 routes (15 active, 0 holddown, 0 hidden)

172.16.4.1/32 (1 entry, 1 announced)

TSI:

KRT in-kernel 172.16.4.1/32 -> {10.0.1.2}

        *IS-IS  Preference: 160

                Level: 1

                Next hop type: Router, Next hop index: 593

                Address: 0x940f04c

                Next-hop reference count: 9

                Next hop: 10.0.1.2 via ge-0/0/0.0, selected

                Session Id: 0x5

                State: <Active Int Ext>

                Age: 1:18:28    Metric: 12

                Validation State: unverified

                Task: IS-IS

                Announcement bits (1): 0-KRT

                AS path: I

---------------------------------------------------------------------

rokk@R1_L1> show route 2001:172:4::1 extensive

inet6.0: 16 destinations, 19 routes (16 active, 0 holddown, 0 hidden)

2001:172:4::1/128 (1 entry, 1 announced)

TSI:

KRT in-kernel 2001:172:4::1/128 -> {fe80::12}

        *IS-IS  Preference: 160

                Level: 1

                Next hop type: Router, Next hop index: 594

                Address: 0x940eff8

                Next-hop reference count: 9

                Next hop: fe80::12 via ge-0/0/0.0, selected

                Session Id: 0x6

                State: <Active Int Ext>

                Age: 1:18:59    Metric: 11

                Validation State: unverified

                Task: IS-IS

                Announcement bits (1): 0-KRT

                AS path: I

Really not a difference.

OK, now let's configure a routing policy on router R1_L1-L2:

rokk@R1_L1-L2> show configuration policy-options

policy-statement OSPF {

    term 1 {

        from {

            protocol ospf;

            route-filter 192.168.2.1/32 exact;

            route-filter 192.168.3.1/32 exact;

            route-filter 192.168.4.1/32 exact;

        then accept;

    term 2 {

        from {

            protocol ospf3;

            route-filter 2001:192:2::1/128 exact;

            route-filter 2001:192:3::1/128 exact;

            route-filter 2001:192:4::1/128 exact;

        then accept;

rokk@R1_L1-L2> show configuration protocols isis

export OSPF;

level 1 disable;

Looks good. Pretty much the same as the policy that was configured on router R2_L1. The only difference is the is also specified the the policy should be exported only as a Level 2 route. Now let's see the routing table from other routers:

R1_L2#show ip route 192.168.4.1

Routing entry for 192.168.4.1/32

  Known via "isis", distance 115, metric 12, type level-2

  Redistributing via isis

  Last update from 10.0.2.3 on Ethernet0/0, 00:02:57 ago

  Routing Descriptor Blocks:

  * 10.0.2.3, from 12.12.12.1, 00:02:57 ago, via Ethernet0/0

      Route metric is 12, traffic share count is 1

R1_L2#show ipv6 route 2001:192:4::1

Routing entry for 2001:192:4::1/128

  Known via "isis", distance 115, metric 11, type level-2

  Route count is 1/1, share count 0

  Routing paths:

    FE80::121, Ethernet0/0

      From FE80::121

      Last updated 00:03:12 ago

For IOS on cisco routers the administrative distance doesn't change for the IS-IS protocol. It's the same for internal and external routes. And it has also different values.

rokk@R2_L1> show route 192.168.2.1

inet.0: 16 destinations, 16 routes (16 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[IS-IS/15] 00:03:06, metric 10

                    > to 10.0.12.13 via ge-0/0/1.0

rokk@R2_L1> show route 2001:192:2::1

inet6.0: 18 destinations, 21 routes (18 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

::/0               *[IS-IS/15] 00:03:16, metric 10

                    > to fe80::122 via ge-0/0/1.0

Ok, but nothing here. Well remember that the policy was exported only as a Level 2 route. And the routers which are only Level 1 will know only what happens inside his area, and for the rest of the routes outside his area it will generate a default route to get there. Let's see if there is a connectivity to the external routes:

rokk@R2_L1> ping rapid 192.168.4.1

PING 192.168.4.1 (192.168.4.1): 56 data bytes

!!!!!

--- 192.168.4.1 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max/stddev = 2.747/3.647/5.547/1.063 ms

rokk@R2_L1> traceroute 192.168.4.1

traceroute to 192.168.4.1 (192.168.4.1), 30 hops max, 40 byte packets

 1  10.0.12.13 (10.0.12.13)  3.529 ms  1.833 ms  1.491 ms

 2  10.0.2.3 (10.0.2.3)  2.923 ms  2.434 ms  2.802 ms

 3  192.168.1.2 (192.168.1.2)  2.751 ms  2.862 ms  3.474 ms

rokk@R2_L1> ping rapid 2001:192:4::1

PING6(56=40+8+8 bytes) 2001:abc:12:12::14 --> 2001:192:4::1

!!!!!

--- 2001:192:4::1 ping6 statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max/std-dev = 4.683/20.166/49.952/17.127 ms

rokk@R2_L1> traceroute 2001:192:4::1

traceroute6 to 2001:192:4::1 (2001:192:4::1) from 2001:abc:12:12::14, 64 hops max, 12 byte packets

 1  2001:abc:12:12::13 (2001:abc:12:12::13)  2.131 ms  1.818 ms  1.257 ms

 2  2001:abc:2::3 (2001:abc:2::3)  3.627 ms  2.759 ms  2.569 ms

 3  2001:abc:192::2 (2001:abc:192::2)  3.000 ms  3.000 ms  2.827 ms

Looks good.

OK, now let's see the metric of IS-IS.

All IS-IS routes have a cost, which is a routing metric that is used in the IS-IS link-state calculation. But, the default metric value is 10 (with the exception of the lo0 interface, which has a default metric of 0).

From here we assume the the link between the routers has always a metric of 10, no matter of the bandwidth of he interface. Let's see if that it's truth.

So for example the route 10.0.2.8/30, which is 2 "hops" away, 2 links and the route to 10.0.1.0/30. I mean from the perspective of router R2_L1-L2. OK, let's see:

okk@R2_L1-L2> show route 10.0.2.8

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

10.0.2.8/30        *[IS-IS/18] 00:12:13, metric 20

                    > to 10.0.2.1 via ge-0/0/0.0

                      to 10.0.2.2 via ge-0/0/0.0

rokk@R2_L1-L2> show route 10.0.1.0

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

10.0.1.0/30        *[IS-IS/15] 02:11:19, metric 20

                    > to 10.0.12.14 via ge-0/0/1.0

                      to 10.0.12.10 via ge-0/0/2.0

Ok, so does this mean that IS-IS doesn't care about the bandwidth of the link? If this is true, then from router R1_L2 to get to the loopback interface of router R2_L2, which is 2.2.2.2/32 should have two equals paths even if one link is 1.5 Mbps an the other link is 100 Mbps? Well let's see:

R1_L2#show ip route

i L2     2.2.2.2 [115/20] via 10.0.2.10, 00:21:44, Serial1/0

                 [115/20] via 10.0.2.2, 00:21:44, Ethernet0/0

R1_L2#show ip route 2.2.2.2

Routing entry for 2.2.2.2/32

  Known via "isis", distance 115, metric 20, type level-2

  Redistributing via isis

  Last update from 10.0.2.10 on Serial1/0, 00:21:35 ago

  Routing Descriptor Blocks:

    10.0.2.10, from 2.2.2.2, 00:21:35 ago, via Serial1/0

      Route metric is 20, traffic share count is 1

  * 10.0.2.2, from 2.2.2.2, 00:21:35 ago, via Ethernet0/0

      Route metric is 20, traffic share count is 1

Well, yes, by default the IS-IS metric, in my opinion, is not recommended. I mean it's behaving just like RIP, an nothing more. But we can change this, by changing the reference bandwidth of the protocol to 1Gig or even better to 10 Gig. OK, let's change this to 1 Gig for simplicity. Here is how we do that:

set protocols isis reference-bandwidth 1g

This is for Junos OS, for IOS you have to specify the metric manual. But let's see the changes for routes 10.0.2.8/30 and 10.0.1.0/30 from the perspective of router R2_L2-L2:

rokk@R2_L1-L2> show route 10.0.2.8

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

10.0.2.8/30        *[IS-IS/18] 00:12:41, metric 11

                      to 10.0.2.1 via ge-0/0/0.0

                    > to 10.0.2.2 via ge-0/0/0.0

rokk@R2_L1-L2> show route 10.0.1.0

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

10.0.1.0/30        *[IS-IS/15] 00:16:00, metric 2

                      to 10.0.12.14 via ge-0/0/1.0

                    > to 10.0.12.10 via ge-0/0/2.0

Earlier the metric was 20 for both of the routes. But now it's different.

The route 10.0.2.8 has a metric of 11 because to get from router R2_L1-L2 to router R1_L2/R2_L2 it costs 1 and from there another 10, because the reference bandwidth was changed only on Junos routers and not of the cisco routers.

The route 10.0.1.0 has a metric of 2 because to get from router R2_L1-L2 to router R1_L1/R2_L1 it costs 1 and from there add another 1.

OK, this is it. Not much, only a long and cool post. But, more on this soon. The video maybe will be more detailed. Just check the page in the next days and the videos will be here.

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