Generally speaking, people tend to configure hsrp for addresses serving as default gateways.
When the client's NIC software initializes & gathers values for the default gateway (dynamically or otherwise), it arps for the gateway's mac address, which, under ideal conditions, is answered by the active member of the HSRP group. If the active member of the HSRP group fails, and the standby ISs can detect this, They will begin answering on behalf of the mac address associated with the ip default gateway address. If the client attempts to speak directly to the other address the router is maintaining on the same ip network it will arp for the BIA of the IS's ethernet interface. ----- Original Message ----- From: "LongTrip" To: Sent: 23 June 2002 12:44 pm Subject: Re: Re: HSRP [7:47177] > So you are saying the client never sees the MAC address of RouterA? It only > sees the MAC address of the "Virtual Router"? > > Kim > > > > > From: "Michael L. Williams" > > Date: 2002/06/23 Sun AM 11:29:24 EDT > > To: [EMAIL PROTECTED] > > Subject: Re: HSRP [7:47177] > > > > This isn't quite right. See comments below. > > > > "Kim Graham" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > This brings up a question. I understand that after the initial "hi I > will > > > be handling your requests please use me as your destination mac address". > > > (Router talking to client). > > > > > > But what happens when the initial router fails and HSRP kicks in? After > an > > > unreachable, would ClientA send out an arp or would RouterB initiate the > > > arping to re-establish connections to any client that was using RouterA > > > after it noticed that RouterA was not responding? > > > > > > Scenario: > > > > > > > > > ClientA ----- RouterA/B(HSRP) ------ ClientB > > > > > > ClientA sends a packet to ClientB > > > ClientA talks to the Virtual RouterA/B -- RouterA/B sends to ClientB > > > RouterA/B tells ClientA -- RouterA will be handling your requests. > > > > Router A never tells Client A that "Router A will be handling your > > requests". As you mentioned, Client A talks to the Virtual Router via the > > Virtual IP address which it ARPs to find the Virtual MAC. Client A never > > knows which of the HSRP routers is "intercepting" and processing it's > > requests.... When Client A sends a frame to the Virtual MAC to go out of > > it's gateway, both Router A and Router B "hear" the packet, but only the > > HSRP Active router will process it. So if, the janitor steps in and > unplugs > > Router A, then after Router B misses enough Hello packets from Router A, it > > declares itself the Active HSRP router for that HSRP group, and at that > > point it starts to process the information sent to the Virtual IP/Virtual > > MAC. This is all transparent to the end clients, Client A in this example. > > So as far as Client A knows, it's still sending traffic to the Virtual IP > > via the Virtual MAC address it has in its ARP cache..... > > > > HTH, > > Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47243&t=47177 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
