1. tcpdump
(1).tcp
sudo tcpdump -w file.log -s 1500 -i eth0
(2).wiresharkで確認
fileterはtcp.port==5432とか。
(3).MTUのフラグメントDF問題
pingで確認
ping -M do -c 1 -s 1500 192.168.1.213
PING 192.168.1.213 (192.168.1.213) 1500(1528) bytes of data.
1508 bytes from 192.168.1.213: icmp_req=1 ttl=64 time=0.013 ms
--- 192.168.1.213 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.013/0.013/0.013/0.000 ms
2. MTU 変更
$ sudo ifconfig eth0 mtu 1350
$ sudo vim /etc/network/if-up.d/mtu
#!/bin/sh
ifconfig eth0 mtu 1350
参考サイト