[ILUG] Network interface order

[P at draigBrady.com]

Niall O Broin wrote:
> I have a Linux router with three NICs, which works fine. I now want to build 
> standby hardware for that so that if it fails anyone can just switch to the 
> standby box by plugging it in, mains and networks, and turning it on. 
> However, if I have three identical NICs in a box how do I know which will 
> become eth0, eth1 and eth2 at boot time?

Well interfaces are ordered in order of driver loading.
However if you have many interfaces handled by one driver
which is usually the case, you are at the mercy of PCI ordering.
Note adding a PCI nic can change the ordering (even taking
precedence over on board nics).

Across boots it shouldn't change so you can always
just hardcode the renaming in a script using
     ip link set dev eth0 name lan
     ip link set dev eth1 name dmz
     ip link set dev eth2 name wan

You can do it based on MAC address using nameif
to handle the case where adding cards changes
the ordering, though I've never had to handle
that situation.

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Pádraig Brady - http://www.pixelbeat.org
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