L2VPN Pseudowire Switching

L2VPN Pseudowire Switching

L2VPN Pseudowire Switching allows the user to extend L2VPN Pseudowires across an inter-AS boundary. This feature connects multiple contiguous pseudowires to form an end-to-end multihop pseudowire.

Network topology:

One Pseudowire VC ID 1000 is established within MPLS-A network between PE1 and PE-AGG1 routers. A second Pseudowire VC ID 10 is established between PE-AGG1 and PE-AGG2 routers. And a third Pseudowire VC ID 2000 is established within MPLS-B network between PE-AGG2 and PE2 routers.

An eBGP session is established between PE-AGG1 and PE-AGG2 routers which is used to send labeled IP packets between two ASes.

Pseudowire Configuration:

First a Pseudowire VC ID 1000 is established between PE1 and PE-AGG1 routers.

Pseudowire between PE1 and PE-AGG1

PE1 router:

interface Loopback 0

 ip address 1.1.1.1 255.255.255.255

 ip ospf 1 area 0

interface Fastethernet 1/0

 description Connected to CE1

 no ip address

 xconnect 2.2.2.2 1000 encapsulation mpls

PE-AGG1 router:

interface Loopback 0

 ip address 2.2.2.2 255.255.255.255

 ip ospf 1 area 0

l2 vfi L2VPN point-to-point

 neighbor 1.1.1.1 1000 encapsulation mpls

Another Pseudowire VC ID 2000 is established within MPLS-B network between PE-AGG2 and PE2 routers.

Pseudowire between PE-AGG2 and PE2

PE-AGG2 router:

interface Loopback 0

 ip address 3.3.3.3 255.255.255.255

 ip ospf 1 area 0

l2 vfi L2VPN point-to-point

 neighbor 4.4.4.4 2000 encapsulation mpls

PE2 router:

interface Loopback 0

 ip address 4.4.4.4 255.255.255.255

 ip ospf 1 area 0

interface Fastethernet 1/1

 description Connected to CE2

 no ip address

 xconnect 3.3.3.3 2000 encapsulation mpls

And a third Pseudowire VC ID 10 is established between PE-AGG1 and PE-AGG2 routers.

Pseudowire between PE-AGG1 and PE-AGG2

PE-AGG1 router:

l2 vfi L2VPN point-to-point

 neighbor 3.3.3.3 10 encapsulation mpls

PE-AGG2 router:

l2 vfi L2VPN point-to-point

 neighbor 2.2.2.2 10 encapsulation mpls

eBGP Connection between PE-AGG1 and PE-AGG2:

An eBGP session is established between aggregating routers. This connection is used to send labeled packets between two ASes.

eBGP Connection

PE-AGG1 router:

interface Fastethernet 1/1

 ip address 172.16.1.1 255.255.255.252

router bgp 100

 neighbor 172.16.1.2 remote-as 200

 neighbor 172.16.1.2 send-label

 network 2.2.2.2 mask 255.255.255.255

PE-AGG2 router:

interface Fastethernet 1/0

 ip address 172.16.1.2 255.255.255.252

router bgp 200

 neighbor 172.16.1.1 remote-as 100

 neighbor 172.16.1.1 send-label

 network 3.3.3.3 mask 255.255.255.255

When neighbor <ip-address> send-label command is configured under BGP, mpls bgp forwarding command is automatically configured under the interfaces connecting the two Aggregating routers.

Automatically generated commands

PE-AGG1 router:

22:07:37.703: %BGP_LMM-6-AUTOGEN1: The mpls bgp forwarding command has been configured on interface: FastEthernet1/1

PE-AGG2 router:

22:07:37.471: %BGP_LMM-6-AUTOGEN1: The mpls bgp forwarding command has been configured on interface: FastEthernet1/0

VC Status verification:

The show mpls l2transport vc [detail] command shows VC status and label stack that will be imposed.

VC Status on PE-AGG1

PE-AGG1# show vfi

Legend: RT=Route-target, S=Split-horizon, Y=Yes, N=No

VFI name: L2VPN, type: point-to-point

  Neighbors connected via pseudowires:

  Peer Address     VC ID

  3.3.3.3          10

  1.1.1.1          1000

PE-AGG1# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status

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

MPLS PW        3.3.3.3:10                 1.1.1.1         1000       UP

MPLS PW        1.1.1.1:1000               3.3.3.3         10         UP

PE-AGG1# show mpls l2transport vc detail

Local interface: MPLS PW 3.3.3.3:10 up

  Destination address: 1.1.1.1, VC ID: 1000, VC status: up

    Output interface: Fa1/0, imposed label stack {16 18}

    Preferred path: not configured

    Default path: active

    Next hop: 10.1.1.5

  Create time: 02:24:47, last status change time: 00:44:08

  Signaling protocol: LDP, peer 1.1.1.1:0 up

    Targeted Hello: 2.2.2.2(LDP Id) -> 1.1.1.1, LDP is UP

    Status TLV support (local/remote)   : enabled/supported

      LDP route watch                   : enabled

      Label/status state machine        : established, LruRru

      Last local dataplane   status rcvd: No fault

      Last local SSS circuit status rcvd: No fault

      Last local SSS circuit status sent: No fault

      Last local  LDP TLV    status sent: No fault

      Last remote LDP TLV    status rcvd: No fault

      Last remote LDP ADJ    status rcvd: No fault

    MPLS VC labels: local 22, remote 18

    Group ID: local 0, remote 0

    MTU: local 1500, remote 1500

    Remote interface description:

  Sequencing: receive transparent, send transparent

  Sequencing resync disabled

  Control Word: On (configured: autosense)

  VC statistics:

    transit packet totals: receive 88, send 77

    transit byte totals:   receive 11342, send 10188

    transit packet drops:  receive 0, seq error 0, send 0

Local interface: MPLS PW 1.1.1.1:1000 up

  Destination address: 3.3.3.3, VC ID: 10, VC status: up

    Output interface: Fa1/1, imposed label stack {22}

    Preferred path: not configured

    Default path: active

    Next hop: 172.16.1.2

  Create time: 02:24:47, last status change time: 00:44:08

  Signaling protocol: LDP, peer 3.3.3.3:0 up

    Targeted Hello: 2.2.2.2(LDP Id) -> 3.3.3.3, LDP is UP

    Status TLV support (local/remote)   : enabled/supported

      LDP route watch                   : enabled

      Label/status state machine        : established, LruRru

      Last local dataplane   status rcvd: No fault

      Last local SSS circuit status rcvd: No fault

      Last local SSS circuit status sent: No fault

      Last local  LDP TLV    status sent: No fault

      Last remote LDP TLV    status rcvd: No fault

      Last remote LDP ADJ    status rcvd: No fault

    MPLS VC labels: local 19, remote 22

    Group ID: local 0, remote 0

    MTU: local 1500, remote 1500

    Remote interface description:

  Sequencing: receive transparent, send transparent

  Sequencing resync disabled

  Control Word: On (configured: autosense)

  VC statistics:

    transit packet totals: receive 77, send 88

    transit byte totals:   receive 10188, send 11342

    transit packet drops:  receive 0, seq error 0, send 0

VC Status on PE-AGG2

PE-AGG2# show vfi

Legend: RT=Route-target, S=Split-horizon, Y=Yes, N=No

VFI name: L2VPN, type: point-to-point

  Neighbors connected via pseudowires:

  Peer Address     VC ID

  4.4.4.4          2000

  2.2.2.2          10

PE-AGG2# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status

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

MPLS PW        4.4.4.4:2000               2.2.2.2         10         UP

MPLS PW        2.2.2.2:10                 4.4.4.4         2000       UP

PE-AGG2# show mpls l2transport vc detail

Local interface: MPLS PW 4.4.4.4:2000 up

  Destination address: 2.2.2.2, VC ID: 10, VC status: up

    Output interface: Fa1/0, imposed label stack {19}

    Preferred path: not configured

    Default path: active

    Next hop: 172.16.1.1

  Create time: 02:13:27, last status change time: 00:42:55

  Signaling protocol: LDP, peer 2.2.2.2:0 up

    Targeted Hello: 3.3.3.3(LDP Id) -> 2.2.2.2, LDP is UP

    Status TLV support (local/remote)   : enabled/supported

      LDP route watch                   : enabled

      Label/status state machine        : established, LruRru

      Last local dataplane   status rcvd: No fault

      Last local SSS circuit status rcvd: No fault

      Last local SSS circuit status sent: No fault

      Last local  LDP TLV    status sent: No fault

      Last remote LDP TLV    status rcvd: No fault

      Last remote LDP ADJ    status rcvd: No fault

    MPLS VC labels: local 22, remote 19

    Group ID: local 0, remote 0

    MTU: local 1500, remote 1500

    Remote interface description:

  Sequencing: receive transparent, send transparent

  Sequencing resync disabled

  Control Word: On (configured: autosense)

  VC statistics:

    transit packet totals: receive 79, send 69

    transit byte totals:   receive 10640, send 8944

    transit packet drops:  receive 0, seq error 0, send 0

Local interface: MPLS PW 2.2.2.2:10 up

  Destination address: 4.4.4.4, VC ID: 2000, VC status: up

    Output interface: Fa1/1, imposed label stack {17 17}

    Preferred path: not configured

    Default path: active

    Next hop: 10.2.2.2

  Create time: 02:13:28, last status change time: 00:42:56

  Signaling protocol: LDP, peer 4.4.4.4:0 up

    Targeted Hello: 3.3.3.3(LDP Id) -> 4.4.4.4, LDP is UP

    Status TLV support (local/remote)   : enabled/supported

      LDP route watch                   : enabled

      Label/status state machine        : established, LruRru

      Last local dataplane   status rcvd: No fault

      Last local SSS circuit status rcvd: No fault

      Last local SSS circuit status sent: No fault

      Last local  LDP TLV    status sent: No fault

      Last remote LDP TLV    status rcvd: No fault

      Last remote LDP ADJ    status rcvd: No fault

    MPLS VC labels: local 21, remote 17

    Group ID: local 0, remote 0

    MTU: local 1500, remote 1500

    Remote interface description:

  Sequencing: receive transparent, send transparent

  Sequencing resync disabled

  Control Word: On (configured: autosense)

  VC statistics:

    transit packet totals: receive 69, send 79

    transit byte totals:   receive 8944, send 10640

    transit packet drops:  receive 0, seq error 0, send 0

The following output proves end-to-end connectivity between two CE routers.

End-to-end connectivity

CE1# ping 192.168.1.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 52/85/160 ms

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