[c-nsp] cisco 3750 arp timeout

[Robert Crowe]

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Matt,

        I believe I ran into the same issue your talking about awhile
back when I was doing systems work. Our issue was with pairs of
servers running Win2k Advanced Server and Microsoft clustering. The
storage was EMC. It ended up being the way Microsoft clustering sends
the gratuitous arp. One way to tell is to failover the services and
immediately do "clear arp" on the switches they are plugged into. We
ended writing a script that would snmp poll the virtual address for
the hostname of the box. When a failover occurred the hostname would
change and the script would telnet to the 2 switches and clear the
arp entries.


- -
Robert Crowe



- -----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Matt Bazan
Sent: Thursday, January 13, 2005 4:49 PM
To: Church, Chuck; cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] cisco 3750 arp timeout

Hi Chuck,
        In this particular case I've got two 3750's in a stack and
several MS clusters attached (one cluster node plugs into stack
member 1, the other node into member 2) and I'm having communication
problems reaching the cluster virtual servers when I 'roll' the
resources over from one node in the cluster to the other.  One of my
theories is that the stack could be having problems with the grat
arps it's getting from the MS cluster.

        As these systems are in our data center I'll have to wait
till the next time I'm over there to put a sniffer on the wire to see
if I can glean more info.

        In the meantime, to attempt to rule out a grat arp issue, I
was trying to get the ciscos to not cache the cluster's virt server
IP and associated MAC. 

  Matt

> -----Original Message-----
> From: Church, Chuck [mailto:cchurch at netcogov.com]
> Sent: Thursday, January 13, 2005 1:19 PM
> To: Matt Bazan; cisco-nsp at puck.nether.net
> Subject: RE: [c-nsp] cisco 3750 arp timeout
>
> Matt,
>
>       On a side note, why are you trying to do this?  Rodney
> mentioned the CEF issue.  Are you trying to speed up HSRP/VRRP or
> something along those lines?  Just curious...
>
>
> Chuck Church
> Lead Design Engineer
> CCIE #8776, MCNE, MCSE
> Netco Government Services - Design & Implementation Team 1210 N.
> Parker Rd.
> Greenville, SC 29609
> Home office: 864-335-9473
> Cell: 703-819-3495
> cchurch at netcogov.com
> PGP key:
> http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x4371A48D 
>
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Matt Bazan
> Sent: Thursday, January 13, 2005 3:23 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] cisco 3750 arp timeout
>
> I've got a number of interfaces on one of my 3750's (IOS 12.1(11)AX
> SMI) that I've set the arp timeout to be one second.  However, the
> entries in the arp cache continue to show up until the default arp
> timeout has been reached.  It was my understanding that setting the
> arp timeout per interface to 1 would clear these entries after 1
> second.  Am I misunderstanding how this command works?  If so, is
> there a command to remove entries from the arp cache after 1
> second?  Thanks,
>
>   Matt
>
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