Possible regression in ifconfig under7.0 - removes valid default route

Jeremy Chadwick koitsu at FreeBSD.org
Mon Nov 17 12:02:53 PST 2008


On Mon, Nov 17, 2008 at 07:11:50PM -0000, Steven Hartland wrote:
> I believe there "may be" a regression in the behaviour of ifconfig or
> possibly just something I've never experienced before.
>
> Basically when changing the IP of one of our machines, it suddenly
> became inaccessible. After some investigation it turned out the machine
> was inaccessible from anything other than the local VLAN and continued
> diagnostics determined that the process of changing the IP had also
> removed the default route.
>
> This was clearly unexpected behaviour as the new IP was on the same
> VLAN as the old IP and hence no routing table updates should be
> required.
>
> I don't have any older machines to test this on but I believe we have
> done this procedure in the past without any such issues so wanted to
> raise it here to see if anyone else has had experience with it.
>
> Even if this isn't a regression it may well be something worth fixing
> as its quite unexpected behaviour which could render a machine totally
> inaccessible.

I can try to reproduce this if you'd like, on a VMware session.

One case where the default route could be (I haven't checked) removed:
some NIC drivers in the past, when changing the "primary IP" (first IP
shown in ifconfig for an interface), would actually bring down the
entire interface (e.g. ifconfig XXX down) then back up again a second or
two later.  dmesg on your machine would be able to confirm whether or
not this is happening.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |



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