Hi Jeff, My understanding is that you are basically going to replace the default gateway for in a couple of vlans. (Same IP but different MAC.)
Active HSRP router will issue gratuitous ARP (gARP) when it becomes Active so there should be little disruption for the hosts inside the vlan trying to reach the default gateway. If hosts ignore gARP then they will try to forward frames to the wrong destination MAC for as long as their ARP entry is valid. Servers usually have ARP timeout of a few seconds to a few minutes where routers can have timeout of 4 hours (like Cisco) or more. HSRP is one thing. You still need to make sure the new routers know how to route packets the same way the old ones did. Good luck, JF Jean-François Dubé Technicien, Opérations Réseau IP Ingénierie Exploitation des Réseaux Vidéotron "cisco-nsp" <[email protected]> a écrit sur 2013-12-30 18:27:12 : > De : Jeff Kell <[email protected]> > A : "[email protected]" <[email protected]>, > Date : 2013-12-30 18:30 > Objet : [c-nsp] Quick question on HSRP... > Envoyé par : "cisco-nsp" <[email protected]> > > Quick question for someone that's been there, done that, as I'm a bit > rushed to try to lab test this... > > We're adding some new routers (4500Xs) for an upgraded server farm > arrangement with a number of server-side vlans / VRFs. The plan was to > trunk it with the existing L3 router, and fire up HSRP (v2) across them > to transition the L3 routing to the new router without being too > terribly disruptive. Not sure if we want to leave the HSRP in place > (thinking yes) or remove it (and the old router) after the migration, > but will cross that bridge when we get there. > > HSRP would place the current "default gateway" as the virtual IP, and I > presume it will pick up a new MAC address. I'm concerned this will > affect the active hosts with the ARP cached for their gateway. The MAC > address would still be valid (should match the original gateway) but the > traffic would be directed to the original (now virtual) IP, as opposed > to the new "physical" gateway on the router. > > So just how "disruptive" will introducing HSRP really be? > > Jeff > > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
