Multiple NIC mapping [SOLVED+HOWTO]

[danomac]

Where to start...

I have 3 NICs in a PC, and I'm wondering how the kernel determines the order they are mapped in. I need to set up 2 as static and one as DHCP, so if eth0 becomes eth1 and vice versa on a reboot, it'll seriously muck things up and the PC's database won't be able to synchronize with another PC.

Is there a way to define a static way to define the mapping? All net modules are compiled directly in the kernel, and 2 of the NICs are of the same chipset.

lspci:

[nielchiano]

IIRC, there are 2 ways: the old nameif-way, and the much better udev way.

For the second way, see this guide. It's best to read it all, but the link should point directly to the interesting part.
You can change eth0 to eth1, but even (like I do) to eth_int or eth_wlan

[danomac]

Perfect, thanks... now I can make sure by MAC address that eth1 is the physical port I think it is.

[nielchiano]

[danomac]

[Bob P]

[nielchiano]

[danomac]

[danomac]

Hmm, maybe I should copy the howto over to the Tips forum.

[Bob P]

Thanks for your detailed tips. I had done the udev thing, and ran into a problem when I renamed the interfaces with an alias. I had renamed eth0, eth1 and eth2 to wan, lan, and dmz, respectively. this seemed to be intuitively obvious and user-friendly naming scheme at the time.

Although the udev rules worked fine, the problem that came up was that the aliasing names really borked shorewall. to get the udev aliases to work, I would have had to rewrite all of the shorewall scripts, replacing all references to eth0, etc. that seemed like an unnecessarily burdensome task, which was something i didn't want to undertake. i was hoping that you had a simple answer, and while i waited for your response i tried another approach.

my approach was to alias all of the eth* statements in udev to rename the devices with the aliases eth0, eth1 and eth2. although it may seem like doing this would be frought with errors, you can do it this way if you're careful enough to perform the assignments in the right order, and assign the interfaces in the numeric order that they're detected by bios on your mobo. (ie: slot ordering). this prevents the user from having to rewrite all of their network dependent scripts. the only downside i've noticed is the undesirable side effect of forcing you to pay attention to slot ordering if you should ever have to change a NIC again.

all things consdiered, its probably just as easy (or even easier) to just pass the ethernet interface configuration information, including the base address and interrupt , via the kernel parameters specificed in grub.conf. as we all know, udev implementation is still incomplete, its still kind of buggy, and over all its still a rapidly moving target in gentoo. at times i wonder if what i work on with udev today will still work next week or next month.

thanks again.
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[danomac]

I've posted it the Documentation, Tips & Tricks forum here as well.

When it comes to configuring iptables/firewalls there's no real easy way other than aliases like you mentioned or editing the scripts. I'd just use grep and see where eth? is mentioned and run a script or something to change the references.

Edit: Wouldn't shorewall have a way to specify the interfaces you are using? I don't use it, but it seems odd that it would just "assume" the WAN side is always eth0!

[Bob P]

[zxy]

@danomac
You made a little mistake, or maybe udev changed.
You should use == instead of = in udev configuration file.

[dtread]

Good afternoon,

I would like to know if there is any way of configuring witch network adapter is eth0 and witch is eth1 and so on.

Regards

[nixnut]

merged above post here.
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