multilayer switches allow HSRP group number reuse on different vlans (with is not possible on router lan subinterfaces that need different HSRP group number).
This gives you the desired scalability regardless of the max number of HSRP different group numbers supported.
I suggest you for HSRP group reuse to use different authentication passwords on each group, in case of an event that makes two different vlans to communicate (error in cabling or some form of bridging loop) they will not consider packets coming from the other vlan.
I realise you can reuse HSRP group numbers on different VLANs and using different passwords is a good idea but I understood there was a limit on the total number of VLANs that could be configured with HSRP.
A 3750 for example can only support 32 VLANs with HSRP.
I think I read that a Supy V can support 256 VLANs with HSRP but I could not find similar detail for the Supy II+
I've explained my understanding in my first post : the limit that is provided is on the number of distinct HSRP group numbers.
Using also the data provided by Victor you can define up to 1000 SVI interfaces.
HSRP is lightweight at L3 level but it has a price to pay on the NIC drivers level:
each distinct HSRP group number uses a different MAC address and each of them fills an entry in the so called packet filter that is the list of unicast and multicast MAC addresses that have to be used to capture traffic to be sent to upper layer protocols to the supervisor.
We had serious problems with HSRP on C7500 and C12000 Engine2 linecards: they have a 31 slots packet filter table and so the problem was that after filling the table the system could crash at the interface level or even at the node level.
0000.0c07.acXY is used by group xy
Those entries were used for the bia, OSPF (2), all routers in subnet and so on.
The workaround for us was to distribute the HSRP active role on both devices evenly.
Multilayer switches allow for HSRP group reuse (that implies also MAC address reuse that it is important).
The limit you are referring are for the number of distinct groups as far as I know.
In release notes it is only noted that HSRP is not supported in the LAN base image
thanks for your information: with 6500 other posters have reported of using 200 HSRP groups without group reusing.
I agree that these figures should be easily accessible.
HSRP is supposed to be vey lightweight but as I wrote in my penultimate post it can pose serious scalability issues at the point that in some platforms like a GSR is more scalable a BGP session that an HSRP group !
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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