Network utils
here's some useful stuff i use to diagnose network problems:
- IP addresses
[root@ariel root]# ip addr 1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 brd 127.255.255.255 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 4: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000 link/ether 00:50:45:5b:d0:8c brd ff:ff:ff:ff:ff:ff inet 207.142.131.244/26 brd 207.142.131.255 scope global eth0 inet6 2001:470:1f01:367:250:45ff:fe5b:d08c/64 scope global deprecated dynamic valid_lft 1897645sec preferred_lft -89555sec inet6 fe80::250:45ff:fe5b:d08c/64 scope link valid_lft forever preferred_lft forever 5: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000 link/ether 00:50:45:5b:d0:8d brd ff:ff:ff:ff:ff:ff inet 10.0.0.2/16 brd 10.0.255.255 scope global eth1 inet6 fe80::250:45ff:fe5b:d08d/64 scope link valid_lft forever preferred_lft forever 6: sit0: <NOARP> mtu 1480 qdisc noop link/sit 0.0.0.0 brd 0.0.0.0
iproute2 is much better than ifconfig; example:
ip addr add 10.0.0.3 dev eth0 .... ip addr del 10.0.0.3 dev eth0
with no need for eth0:X virtual interfaces
ip route add default via 10.0.0.4
- packet sniffing; tcpdump:
tcpdump -s 1520 -lni eth0 host bacon and port not 22
(exclude port 22 to avoid seeing your own traffic)
- or tethereal (nicer for some things, can decode http requests, mysql data streams etc):
tethereal -s 1520 -ni eth0 host bacon and port not 22
- arping: like ping but uses ARP instead of ICMP (gets through firewall on the LAN)