How many SVI's can be part of a GLBP group

[michaelarigan]

I have 2 nexus 7000's each currently running HSRP, All the SVI's are in 2 HSRP groups, my question is how many SVI's can be asocaited with 1 GLBP group? Does the Group have to be different for each VLAN? How many GLBP groups can be configured on the Nexus ?

[paul driver · Accepted solution]

Hello,

You have stated HRSP then GLBP which are configured roughly the same but GLBP is specifically for LoadSharing  and HRSP/VRRP is specifically for redundancy,

GLBP supports up to 1024 virtual routers (GLBP groups) on each physical interface of a router and up to four virtual forwarders per group.

http://www.cisco.com/en/US/docs/ios-xml/ios/ipapp_fhrp/configuration/xe-3s/fhp-glbp.html#GUID-26C72408-6183-415A-9949-8B97542246A9

http://www.cisco.com/en/US/docs/ios-xml/ios/ipapp_fhrp/configuration/xe-3s/fhp-hsrp.html#GUID-0C469257-64CB-4779-B9FC-964A2E051789

res

Paul

Please don't forget to rate this post if it has been helpful.

[Giuseppe Larosa · Accepted solution]

Hello Michael,

multilayer switches allow for re-using the same HSRP group number over multiple SVIs.

Actually this is recommended on low end / mid range multilayer switches as a way to achieve scalability as the systems are limited to be able to process only a few different HSRP related MAC addresses.

However, this limitation is not present in C6500, and it is likely not present on Nexus 7000.

When re-using the same HSRP group number over different SVIs I would suggest to use a different MD5 password on each SVI, so that, if by accident two broadcast domains are joined, the devices will not start to complain of receiving HSRP messages from not connected IP subnets.

So to answer your question you can re-use the same HSRP group number over many SVIs as you are actually already doing. Multilayer switches implementation of HSRP is different from that of SW based routers in this aspect.

Hope to help

Giuseppe

[michaelarigan]

Thank you for the answer! I have a follow up question maybe you can help with.  I noticed while wiresharking a SPAN session of a IP phone that it wsa recieving multicast packets form the GLBP with the Multicast address of 224.0.0.102. it would seem that GLBP packets is being sent out to all nodes on the access Level.  I have also implemented IGMP snopping  and seems to not have helped.

Is there a way to prevent this from happening?

Again thank you for the previous answer

[Giuseppe Larosa]

Hello Michael,

thanks for your kind rating

IGMP snooping  does not operate on link local multicast addresses in 224.0.0.0/24 range, so what you see should be normal.

The IP Phone likely discards the frame at NIC driver level, it shouldn't be an issue.

Hope to help

Giuseppe

[michaelarigan]

Awesome Thanks again!

Michael Arigan
CCNP