Wonky Ping (ping don't work)

Denys Vlasenko vda.linux at googlemail.com
Tue Apr 21 01:48:29 UTC 2009


On Tuesday 21 April 2009 03:01, Chris Plasun wrote:
> start           192.168.0.100   #default: 192.168.0.20
> end             192.168.0.120   #default: 192.168.0.254
> .
> .
> .
> opt     dns     192.168.10.2 192.168.10.10
> option  subnet  255.255.255.0
> opt     router  192.168.10.2

You can't reach router at 192.168.10.2
if you are on 192.168.0.x network.

> opt     wins    192.168.10.10
> option  dns     129.219.13.81   # appened to above DNS servers for a total of 3
> option  domain  local
> option  lease   864000          # 10 days of seconds
> 
>  > Not enough data. What is your udhcpc script?
> > /etc/resolv.conf contents?
> 
> resolv.conf (values correct):
> nameserver 64.59.144.18
> nameserver 64.59.144.19
> 
> > "ip a"
> 1: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
>     link/ether 00:e0:0c:00:95:01 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.1.100/24 brd 192.168.1.255 scope global eth0
> 2: eth1: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
>     link/ether 00:e0:0c:00:95:02 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.1.207/24 brd 192.168.1.255 scope global eth1
> 3: lo: <LOOPBACK,UP,10000> 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 scope host lo
> 
> > "ip r" 
> 192.168.1.0/24 dev eth0  src 192.168.1.100
> 192.168.1.0/24 dev eth1  src 192.168.1.207
> 127.0.0.0/8 dev lo
> default via 192.168.1.1 dev eth1

How would kernel know which interface to use to send a packet to 192.168.1.1 -
eth0 or eth1? It probably would use eth0, just because it comes first...
...kaboom.

Deconfigure eth0 (or eth1) and use the other one.

> > How exactly your ping command looks like?
> 
> ping 192.168.1.1
> 
> > What tcpdump -nl -ieth1 shows?
> 
> Apparently the board doesn't have that...

You can run it on any network-attached machine.
--
vda


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