[ILUG] Ubuntu networking questions

[Niall O Broin]

On 23 Feb 2006, at 15:59, Stephen Shirley wrote:

> Depends how you look at it. According to ifconfig/ifup/ifdown, yes, 
> it's
> a seperate interface. But to all practical intents and purposes, and
> according to iproute, it's not. ifconfig is deprecated, iproute is
> preferred.
>
> 2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
>     link/ether 00:c0:4f:bb:25:da brd ff:ff:ff:ff:ff:ff
>     inet 193.1.99.120/26 brd 193.1.99.127 scope global eth0
>     inet 136.201.105.1/24 brd 136.201.105.255 scope global eth0:1

Note the eth0:1 there - a different virtual interface. If you had done

ip addr add 136.201.105.1/24 eth0

then the output above would have finished


inet 193.1.99.120/26 brd 193.1.99.127 scope global eth0
inet 136.201.105.1/24 brd 136.201.105.255 scope global secondary eth0

which is subtly different and as Colm pointed out earlier, CAN be 
problematic in certain cases.



Niall