gratuitous ARP with em interface.
akanwar at digitarchy.com
akanwar at digitarchy.com
Thu May 29 16:52:47 PDT 2003
Thanks all for you replies.
> I haven't tried this, but I think the problem would go away if you
> changed WAIT_FOR_AUTO_NEG_DEFAULT to 0 in "if_em.h".
Changed this. Did not work.
> If u can do kernel debugging put break point at the
> "arp_ifinit" and verify if this was getting called or
> not.................. cheers, mahesh
Will try this.
> Could be attributed to the spanning tree in the switch.I have
> seen it happening(especially with cisco switches).I bet you
> are not able to send out any packet(Not just Garp).
No. Spanning tree is turned off (Tried it with both IOS and Catalyst
switches).
> I haven't looked that deep into why, but em is quite slow
> on coming up compared to fxp for example. Probably something to do with
> hardware re-initialization.
Correct, there is a delay. "ifconfig em0 inet x.x.x.x/y" takes a few
seconds to complete whereas "ifconfig fxp0 inet x.x.x.x/y" returns
instantly.
Is there a way to force gratituous arp ? ( Short of writing a raw socket
utility)
Thanks,
-ansh
> > >On Wed, May 28, 2003 at 07:57:07PM -0400,
> > akanwar at digitarchy.com wrote:
> > >
> > >
> > >>Hi all,
> > >>
> > >>Is there a known issue with alias IPs on em interfaces not
> > sending out
> > >>gratuitous arps ?
> > >>
> > >>The situation is as follows:
> > >> I am running a custom redundancy daemon that migrates the
> > IP address
> > >>of a server from one interface to another in case the
> > active network
> > >>path fails. Till now I was experimenting with two fxp
> > interfaces and
> > >>everything worked perfectly. i.e. when the ip address moved over
> > >>(using a perl script to run ifconfig commands) it sent out
> > grat. arps
> > >>for each of its alias IPs. This allowed the router to
> > update its Arp
> > >>table and talk to the newly active interface.
> > >>
> > >>Now when I try running the code with em (gigabit Ethernet
> > over copper)
> > >>NICs, I simply do not see the gratuitous arps come out of the new
> > >>interface.
> > >>
> > >>I am at a loss to understand what has changed. Could it
> be that the
> > >>line DOWN -> UP time of the em interface is longer thereby
> > causing a
> > >>loss of ARPs ? Any suggestions ?
> > >>
> > >>
> > >>
> > >Yes, I can reproduce this too, no gratuitous ARP is sent.
> > >
> > >
> > >Cheers,
> > >
> > >
> >
> >
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