Thanks Giuseppe

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+

rgds

Allan

Allan:

2,000 L2 vlans and 1,000 SVIs

http://www.cisco.com/en/US/prod/collateral/modules/ps2797/ps5347/product_data_sheet09186a0080197424_ps4324_Products_Data_Sheet.html

HTH

Victor

Hello Allan,

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.

Note:

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

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/release/note/OL_17886.html

Hope to help

Giuseppe

Giuseppe.

There is a limitation on how many VLAN you can configure HSRP onto in the Cat3560/3750 switches, even if you reuse the group number, and that figure is 32.

I believe that the limit is much higher in Cat4500, as well as in Cat3560E/3750E and Cat6500, but it would be nice to know if Cisco has a specific document stating these numbers.

Ingolf

Hello Ingolf,

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 !

Hope to help

Giuseppe

Right!

The unit which runs HSRP has to be a Layer 3 device as HSRP is a way to make the default gateway redundant, and an end-host like a Layer 2 switch cannot be the default gateway for anything.

So our comemnts regarding numbers of HSRP groups etc. goes for those Supervisors for Cat4500 which are Layer 3.

Sorry for any confusion caused.