The following deals with bug in ping that made it very difficult to set up a system with two gateways.
ping -I is broken
Demonstration that ping -I is broken. When specifying the source
interface using -I with an ethX alias and that interface is not the default gateway
interface, then ping fails. When specifying the interface as an ip address,
ping works. Search for "Destination Host Unreachable" to find the bug.
eth0 = 4.3.2.8 and the default gateway is accessed through a different interface eth1.
eth1 = 192.168.168.155 is used as the device to get to the default gateway. FAILS : ping -I eth0 208.67.222.222 WORKS: ping -I 4.3.2.8 208.67.222.222 WORKS: ping -I eth1 208.67.222.222 WORKS: ping -I 192.168.168.155 208.67.222.222
The following are actual results which can be reproduced from an up-to-date
Fedora 11 or CentOS 5.3 box. Caused a very very long episode of frustration
when setting up multi gatewayed systems.
ping using eth0 :
ping -c 2 -B -I eth0 208.67.222.222 PING 208.67.222.222 (208.67.222.222) from 4.3.2.8 eth0: 56(84) bytes of data. From 4.3.2.8 icmp_seq=1 Destination Host Unreachable From 4.3.2.8 icmp_seq=2 Destination Host Unreachable
ping -c 2 -B -I 4.3.2.8 208.67.222.222 PING 208.67.222.222 (208.67.222.222) from 4.3.2.8 : 56(84) bytes of data. 64 bytes from 208.67.222.222: icmp_seq=1 ttl=55 time=562 ms
64 bytes from 208.67.222.222: icmp_seq=2 ttl=55 time=642 ms
--- 208.67.222.222 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 562.546/602.400/642.255/39.862 ms
ping using eth1 :
ping -c 2 -B -I eth1 208.67.222.222 PING 208.67.222.222 (208.67.222.222) from 192.168.168.155 eth1: 56(84) bytes of data. 64 bytes from 208.67.222.222: icmp_seq=1 ttl=54 time=270 ms
64 bytes from 208.67.222.222: icmp_seq=2 ttl=54 time=629 ms
--- 208.67.222.222 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 270.128/449.766/629.405/179.639 ms
ping using 192.168.168.155 :
ping -c 2 -B -I 192.168.168.155 208.67.222.222 PING 208.67.222.222 (208.67.222.222) from 192.168.168.155 : 56(84) bytes of data. 64 bytes from 208.67.222.222: icmp_seq=1 ttl=54 time=585 ms
64 bytes from 208.67.222.222: icmp_seq=2 ttl=54 time=554 ms
--- 208.67.222.222 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 554.098/569.655/585.212/15.557 ms
My source route policy rules:
/sbin/ip rule show 0: from all lookup 255 32762: from 4.3.2.8 lookup nic0 32763: from 192.168.168.155 lookup nic1 32764: from 192.168.168.155 lookup nic1 32765: from 4.3.2.8 lookup nic0 32766: from all lookup main
32767: from all lookup default
Print out routing tables using /sbin/ip route show table TABLENAME: routing table nic0 : /sbin/ip route show table nic0 default via 4.3.2.1 dev eth0
routing table nic1 : /sbin/ip route show table nic1
default via 192.168.168.1 dev eth1
routing table main : /sbin/ip route show table main 4.3.2.1/27 dev eth0 proto kernel scope link src 4.3.2.8 192.168.168.0/24 dev eth1 proto kernel scope link src 192.168.168.155 169.254.0.0/16 dev eth1 scope link default via 192.168.168.1 dev eth1
routing table default : /sbin/ip route show table default
NOTES:
cat /etc/iproute2/rt_tables to get your own table names.
man ping: -I interface address Set source address to specified interface address. Argument may be numeric IP address or name of device. When pinging IPv6 link-local address this option is required.
ping -V returns the latest available on CentOS and Fedora and the maintainers website:
ping utility, iputils-ss020927