Re: ARP / Cisco Router Wierdness
Peter Pauly <[EMAIL PROTECTED]> wrote: > This morning while attempting to replace a server with a new machine > (same IP address, the old machine was unplugged), The Cisco 2600 > router's arp table continued to point to the old DNS server's MAC > address. > > Even after rebooting the new server (Freebsd 5.2.1), the MAC address > remained unchanged in the router. The router continued to point to the > old machine's MAC address. > > I updated the entry manually in the router and all was well. But I am > concerned that Freebsd is not announcing it's MAC address when the > machine or interface comes up. Any ideas? I'm not an ARP expert, but isn't it the job of the device maintaining an ARP table to properly time out and refresh the entries in that table? I.e. shouldn't you be posting this question to a Cisco mailing list, asking why the 2600 didn't automatically pick up the new MAC address? Corrections are welcome if I'm wrong on this count. -- Bill Moran Potential Technologies http://www.potentialtech.com ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: ARP / Cisco Router Wierdness
This behavior is consistent with most IOS based routers I've worked around, they typically hold onto an ARP entry for about 20 minutes before expiring it. On linux I've used a network utility called send_arp that can shoot a user specified gratuitous arp packet at another host on the same layer2 network. I'm sure there are other tools available to do the same from freebsd (if you don't have administrative access to the cisco to clear the arp cache). I'm not sure if I like cisco routers by default being willing to accept an arp response that it didn't request, but that's a different issue. On Fri, 25 Jun 2004, Peter Pauly wrote: > This morning while attempting to replace a server with a new machine > (same IP address, the old machine was unplugged), The Cisco 2600 > router's arp table continued to point to the old DNS server's MAC > address. > > Even after rebooting the new server (Freebsd 5.2.1), the MAC address > remained unchanged in the router. The router continued to point to the > old machine's MAC address. > > I updated the entry manually in the router and all was well. But I am > concerned that Freebsd is not announcing it's MAC address when the > machine or interface comes up. Any ideas? > ___ > [EMAIL PROTECTED] mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "[EMAIL PROTECTED]" > ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: ARP / Cisco Router Wierdness
Hi, - Original Message - From: "Bill Moran <[EMAIL PROTECTED]>" To: To Peter Pauly Date: Fri, 25 Jun, 2004 15:21 BST Subject: Re: ARP / Cisco Router Wierdness > Peter Pauly <[EMAIL PROTECTED]> wrote: > > > This morning while attempting to replace a server with a new machine > > (same IP address, the old machine was unplugged), The Cisco 2600 > > router's arp table continued to point to the old DNS server's MAC > > address. > > > > Even after rebooting the new server (Freebsd 5.2.1), the MAC address > > remained unchanged in the router. The router continued to point to the > > old machine's MAC address. > > > > I updated the entry manually in the router and all was well. But I am > > concerned that Freebsd is not announcing it's MAC address when the > > machine or interface comes up. Any ideas? Cisco routers (depending on IOS version) will cache arp entries for at least 20 mins. To force an update, simply run "clear arp" on the router and any Cisco IOS-based switches as well. Regards, Stacey > > I'm not an ARP expert, but isn't it the job of the device maintaining an > ARP table to properly time out and refresh the entries in that table? > > I.e. shouldn't you be posting this question to a Cisco mailing list, > asking why the 2600 didn't automatically pick up the new MAC address? > > Corrections are welcome if I'm wrong on this count. > > -- > Bill Moran > Potential Technologies > http://www.potentialtech.com > ___ > [EMAIL PROTECTED] mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "[EMAIL PROTECTED]" pgppCYlhJxF1b.pgp Description: PGP signature
