Maximum HSRP group in CAT 6509

MKCHAURASIA · ‎08-15-2008

I have to configure HSRP but the prob is my 6509 support only 16 HSRP group in the present config vlan100 belongs to group 100 so can I assign same HSRP group to other VLAN as well with different standby IP

config is below

CORE 1

interface vlan100

ip add 10.197.208.3 255.255.255.0

standby 100 ip 10.197.208.1

standby 100 preempt

standby 100 priority 110

CORE 2

interface vlan100

ip add 10.197.208.2 255.255.255.0

standby 100 ip 10.197.208.1

standby 100 preempt

configure a new VLAN with with same HSRP group but with different standby IP

CORE 1

interface vlan500

ip add 10.197.213.3 255.255.255.0

standby 100 ip 10.197.213.1

standby 100 preempt

standby 100 priority 110

CORE 2

interface vlan500

ip add 10.197.213.2 255.255.255.0

standby 100 ip 10.197.213.1

standby 100 preempt

is this config correct ?

the change that i make is assign different standby IP add to same instance of HSRP group in this case 100

now my HSRP group count is not exceeded by group 100 has to diffent stanby IP

Thanks ...

Giuseppe Larosa · ‎08-15-2008

Hello Manish,

this is possible and best practice for some multilayer implementations of HSRP.

The limitation comes from the fact that every HSRP group consumes an entry in the list of unicast MAC addresses that have to be processed at the NIC level.

Here on multilayer switches, the switch can distinguish frames of different L2 vlans because they have different layer 2 802.1Q tags for example. So it's safe to reuse the same HSRP group number on different Vlans.

You cannot do this on vlan subifs of a router.

Hope to help

Giuseppe

MKCHAURASIA · ‎08-15-2008

Hello Giuslar,

Thank you for your reply, so this means we can have virtually any number of vlans (ofcourse the maximum vlan allowed) beloging to same group number but with different stand-by IP add.

and we dont need to worry about the number of HSRP group supported for any given MSFC