Troy,
The HSRP routers use a virtual MAC address. When the backup router does not
get a hello packet, it send out a frame with the same virtual MAC address.
The switch see the MAC address and think that the interface had move from
one port to another. It will immediately start to send frames to the new
port.
Albert
"Troy C" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Nat,
>
> This is one of those things that differientiate [sp?] a _LOGICAL_
> drawing and a _PHYSICAL_ drawing. Figure 9-3 on that page shows
> "Network 3.0.0.0" and "Network 2.0.0.0" This is a logical drawing.
> These networks could be utilizing a HUB, Switch, or a direct connect
> such as a cross-over cable. Typically, in the real world [assuming
> you meant in a production enviroment] it is a switch.
>
> Now, let's assume it is a switched network. The switch wouldn't send
> out any "hello" type packets. The HRSP protocol is a _router_
> protocol. So the routers are talking to each other, ensuring the
> primary is alive and well, and if not, a take over by the secondaries.
> The switch is just the medium.
>
> But this brings up another question that I had not found until you
> posted the link. And that was what about layer-2? IE: MAC address
> resolution. How did a switch, using VLANs quite possibly, ensure it
> went to the correct MAC address?
>
> From that link:
> ..." When you configure HSRP, the router automatically selects one of
> the virtual MAC addresses from a range of addresses in the Cisco IOS
> software that is within the range of Cisco's MAC address block"...
>
> Aha! So the MAC address stays the same [as does the associated IP
> address] But wait! How does the switch _relearn_ where that MAC
> address is?
>
> In other words:
>
> Primary router A, with IP of 1.1.1.1 and Mac adder of x:x:x:x is off
> switch port 5. Router A dies, and Router B takes over...using IP
> 1.1.1.1 and Mac adder of x:x:x:x now on switch port 8. But the switch
> still thinks x:x:x:x is on switch port 5. How does he get updated??
> [besides arp table purge] Yet to figure this one out...but I will
> keep you updated, as I have been put on the HA [High Availability]
> Project where I work.
>
> FWIW, We are also looking at Cisco's Local director, F5's BigIP/3DNS,
> and a combination of pure physical redundancy.
>
> Troy Coulombe
> Network Engineer, CCNA
> ...and all around nice guy
>
>
>
> On 28 May 2000 03:17:35 -0400, [EMAIL PROTECTED] wrote:
>
> >Hola newbies. I had a question that went unanswered a while back about
load
> >balancing and backup. I found the answer to it tonight. See this link for
> >information:
> >
>
>http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2022.htm#xtocid1851
22
> >
> >Now for those of you in the real world.....no where in this doc do I see
a switch. If there were one, do you just tell it to accept traffic from any
> >of the routers, and are there weights or values to do this? Does the
switch send some kind of hello packet to find out who the main router is
> >or what???
> >
> >Thanks!
> >
> >Nat
> >CCNA. MCSE, CNA
> >
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