From: Mas Kato (loomis_towcar@xxxxxxxxxxxxxx)
Date: Tue Apr 16 2002 - 03:35:51 GMT-3
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Bill,
Yes, a VMAC is created and by default takes the form 0000.0C07.ACxy, where xy=t
he group number in hex. It can be overriden by using the 'standby mac-address'
command.
Regarding using the BIA, one thing that comes to mind is there were certain har
dware interfaces that needed to reset themselves after taking on the new MAC ad
dress. This, in conjunction with the spanning-tree forwarding delay of an exter
nally-connected switch, would sometimes cause the interfaces to constantly flap
between the standby and active states. I don't know if the 6000 series interfa
ces need to reset, although I doubt it. The other thing is certain switches imp
lement a form of loop detection when the same MAC address appears on more than
one interface within a certain interval. Instead of immediately updating the fo
rwarding table and moving frames, frames with that MAC address are dropped for
the interval.
You typically do not have to clear any ARP caches or bridge forwarding tables b
ecause the appropriate interface will issue a gratuitous ARP reply when it beco
mes active for the group.
Some other things you might want to think about might include tracking the stat
e of an important upstream interface for efficiency, preemption for control of
the normal active state and deciding whether it's worth doing additional traffi
c engineering if any asymmetrical routing occurs.
Regards,
Mas Kato
https://ecardfile.com/id/mkato
> "Bill Mckenzie" <bmckenzie@hotmail.com> ccielab@groupstudy.com HSRPDate: Mon,
15 Apr 2002 22:03:17 +0000
>Reply-To: "Bill Mckenzie" <bmckenzie@hotmail.com>
>
>I have a question about HSRP.
>
>Here's the scenario: We have a collapsed backbone structure, with Cat 6509
>switches with Routing Modules as the Distribution\Core Switches. We want to
>implement HSRP on the two 6509's. My question is, when activating the HSRP
>group, does it create it's own virtual mac address? Also, why would you ever
>want to use the burned in Address? All the Vlans use the same mac address
>(which is the mac of the switching module). Do you have to clear the arp
>cache on the servers to get the new mac of the new gateway? Are there any
>other issues someone has encountered when trying to implement this? I don't
>want anything unforseen to sneak up on me.
>
>
>Thanks,
>Bill Mckenzie
>
>
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