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Examples:

It is time for a more complicated example. Let us add an invalid gatewayed route for a destination which is really directly connected:

netadm@alisa:~ # ip route add 193.233.7.98 via 193.233.7.254
netadm@alisa:~ # ip route get 193.233.7.98
193.233.7.98 via 193.233.7.254 dev eth0  src 193.233.7.90
    cache  mtu 1500 rtt 3072
netadm@alisa:~ #
and probe it with ping:
netadm@alisa:~ # ping -n 193.233.7.98
PING 193.233.7.98 (193.233.7.98) from 193.233.7.90 : 56 data bytes
From 193.233.7.254: Redirect Host(New nexthop: 193.233.7.98)
64 bytes from 193.233.7.98: icmp_seq=0 ttl=255 time=3.5 ms
From 193.233.7.254: Redirect Host(New nexthop: 193.233.7.98)
64 bytes from 193.233.7.98: icmp_seq=1 ttl=255 time=2.2 ms
64 bytes from 193.233.7.98: icmp_seq=2 ttl=255 time=0.4 ms
64 bytes from 193.233.7.98: icmp_seq=3 ttl=255 time=0.4 ms
64 bytes from 193.233.7.98: icmp_seq=4 ttl=255 time=0.4 ms
^C
--- 193.233.7.98 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 0.4/1.3/3.5 ms
netadm@alisa:~ #
What happened? Router 193.233.7.254 understood that we have a much better path to the destination and sent us an ICMP redirect message. We may retry ip route get to see what we have in the routing tables now:
netadm@alisa:~ # ip route get 193.233.7.98
193.233.7.98 dev eth0  src 193.233.7.90 
    cache <redirected>  mtu 1500 rtt 3072
netadm@alisa:~ #


next up previous contents
Next: ip rule Up: ip route get Previous: Output format:   Contents
Martin A. Brown 2003-03-14