SUMMARY Dual Ethernet fail-over?

From: Bill Fenwick <>
Date: Wed Apr 25 2001 - 15:14:06 EDT
My apologies for this long-overdue summary, and thanks to the two folks who asked
me if I'd gotten any responses and nudged me into posting this.

Original question:

> We're in the midst of putting together a proposal, and the client wants pretty
> much everything on the machines to be redundant, including at least two
> connections to the 10/100Base-T network for each machine.  The hope with this
> type of setup is that if one NIC should fail for some reason, they could
> simply use the other one and not have to lose the connection and take the
> machine down immediately to replace the card.
> All well and good, but my question is, is it possible to set this kind of
> redundancy up so that if one card does fail, the other can be used without any
> outside interference, i.e. switching the host name the particular machine is
> referred by?  Or is this automatically done anyway?  I remember putting a
> second NIC into a Sun server a few years ago (a 3000, maybe?) but I don't
> recall being able to set it up so that the second card would "take over"
> automatically if the first one failed.  I've been trying to find some mention
> of this kind of thing in the documents at with no luck.
> Again, I apologize if this is a dumb question.  I haven't been able to search
> the archives for a couple days for some reason.  TIA and IWS.

Thanks to the following for their responses:

William Yodlowsky <>
Toby Rider <>
Doug Otto <>
Mike Salehi <>
Jeff Woolsey <>
Mike White <>
Patrik Malinen <>
John Malick <>
Ryan Madison <>
William Hathaway <>
Christophe Dupre <>
Daniel Feenberg <>
Seth Rothenberg <>
Ivan Kovalev <>
Darren Dunham <>
Blake Matheny <>
David Byers <>
Changa Anderson <>
Michael Hill <>
Marc Alvidrez <>
Josh McCormick <>
Robert Alexander <>
Michael Cunningham <>
Chad Rytting <>
Gary Jenson <>
Marco Greene <>

The responses generally fell into three categories:

1.  If you're using Solaris 8 MU3 (10/00) or later, IP multi-pathing is
built-in.  A PDF document is available at and does a good job
explaining it.

2.  If you're using an earlier version of Solaris, you can use Sun Trunking with
an appropriate switch to "combine" up to four interfaces into one virtual
interface.  Sun Trunking is intended to increase bandwidth, but if an interface
fails, the other(s) will automatically pick up the slack (bandwidth will, of
course, be slower then).  There's more on Sun Trunking available at .

3.  You can write a script that pings the first interface and, if there's no
response, configures the second one.

I expect we'll be going with the first option.

Bill Fenwick                            Email:
Digicomp Research                       Voice:  (607) 273-5900 ext 32
Received on Wed Apr 25 20:14:06 2001

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