[c-nsp] cisco 3750 arp timeout

[Rodney Dunn]

Yeah.  From what I remember you would send
the arp request then you send one last chance
to get it.

200_#clear arp
200_#
3d00h: %SYS-5-CONFIG_I: Configured from console by console
*Jan 13 20:48:22.978: IP ARP: sent req src 1.1.1.1 aabb.cc00.c800,
                 dst 1.1.1.2 aabb.cc00.c900 Ethernet0/0
*Jan 13 20:48:22.998: IP ARP: rcvd rep src 1.1.1.2 aabb.cc00.c900, dst 1.1.1.1 E
thernet0/0
*Jan 13 20:48:22.998: IP ARP: creating entry for IP address: 1.1.1.2, hw: aabb.c
c00.c900

1 minute later I send a refresh attempt:

200_#
*Jan 13 20:49:24.082: IP ARP: sent req src 1.1.1.1 aabb.cc00.c800,
                 dst 1.1.1.2 aabb.cc00.c900 Ethernet0/0

Didn't get a response because I shut 1.1.1.2 down.

and then 60 seconds later it sends one last effort to get it
and no response it's removed:

200_#
*Jan 13 20:49:24.082: IP ARP: sent req src 1.1.1.1 aabb.cc00.c800,
                 dst 1.1.1.2 aabb.cc00.c900 Ethernet0/0
200_#
*Jan 13 20:50:24.082: IP ARP: sent req src 1.1.1.1 aabb.cc00.c800,
                 dst 1.1.1.2 aabb.cc00.c900 Ethernet0/0
200_#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  1.1.1.1                 -   aabb.cc00.c800  ARPA   Ethernet0/0


I don't know when but in future code it will all be made event
driven so the 60 second timer dependency will be removed.

Rodney

On Thu, Jan 13, 2005 at 12:46:42PM -0800, Matt Bazan wrote:
> I set the timeout to be 60 but I still see them aging past 1
> minute..ideas? 
> 
> > -----Original Message-----
> > From: Rodney Dunn [mailto:rodunn at cisco.com] 
> > Sent: Thursday, January 13, 2005 12:37 PM
> > To: Matt Bazan
> > Cc: cisco-nsp at puck.nether.net
> > Subject: Re: [c-nsp] cisco 3750 arp timeout
> > 
> > I'm pretty sure this has not changed recently.
> > There is a background process that ages the
> > arp entries and it runs every 60 seconds so
> > 60 should be a minimum setting.
> > Actually the minimum I would ever recommend
> > is 120 seconds due to the CEF adjacency entries.
> > 
> > Rodney
> > 
> > 
> > On Thu, Jan 13, 2005 at 12:22:47PM -0800, Matt Bazan wrote:
> > > 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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> >