Linux 網路不通先檢查 ARP

通常是將實體網路更換 switch PORT 或是更換 IP 後，發現網路不通的狀況..

• 可以先用 arping <gateway ip> 讓 switch 更新 arp table

[root@pd920 ~]# arping 192.168.11.254
ARPING 192.168.11.254 from 220.130.131.239 eth0
Unicast reply from 192.168.11.254 [00:90:1A:82:83:FE]  41.405ms
Unicast reply from 192.168.11.254 [00:90:1A:82:83:FE]  41.848ms
Unicast reply from 192.168.11.254 [00:90:1A:82:83:FE]  41.642ms
Unicast reply from 192.168.11.254 [00:90:1A:82:83:FE]  38.575ms
Unicast reply from 192.168.11.254 [00:90:1A:82:83:FE]  39.111ms
Sent 5 probes (1 broadcast(s))
Received 5 response(s)

• 用 arp -a 看看本身的 arp table 是否正確

[root@pd920 ~]# arp -a
220-130-131-254.HINET-IP.hinet.net (220.130.131.254) at 00:90:1A:82:83:FE [ether] on eth0
? (192.168.11.254) at 00:90:1A:82:83:FE [ether] on eth0
www.ichiayi.com (220.130.131.240) at 00:13:74:00:5C:xx [ether] on eth0
vm-mail.ichiayi.com (192.168.11.236) at 00:0C:29:48:E8:13 [ether] on eth1