If you are placing lots of HSRP groups on the same interface I would imagine at some point hello traffic would become an issue... I guess it really depends on the bandwidth and how aggressively you tune your timers...
Bill -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Justin Shore Sent: Monday, December 22, 2008 4:07 PM To: Arie Vayner (avayner) Cc: Cisco-nsp Subject: Re: [c-nsp] Sharing HSRP group numbers across multiple HSRP instances Arie & Christian, Thanks for the replies. So re-using HSRP group #s doesn't create any conflicts? That's good to know. It also won't reduce the load? That's unfortunately. For some reason I had it in my mind that you could create some sort of collective HSRP instance over a common L2 infrastructure that would share hellos and switch as one common unit. It would be list MST for HSRP essentially. One design scenario I didn't ask about was if I could do the same thing with HSRP instances on sub-ints of a router. On the other end of these MPLS/VPNs is a pair of ISRs facing a 3560 with 1Q trunks. On each ISR is an int facing the 3560 and that int is broken up into several sub-ints. I have HSRP instances on those as well. I have a matching instance on each ISR for each customer VLAN. However I just tried to create a new sub-int with the same HSRP group # and it yelled at me. Apparently it isn't supported on the same physical interface. % Must use unique HSRP group number for each logical interface that is a member of the same physical interface. This isn't a problem for me. Our contiguous L2 infrastructure isn't so big that 4096 HSRP group numbers won't handle it. I doubt if we'll have more than 1000 before I'm breaking it up into smaller pieces for bandwidth reasons. Thanks for the info Justin Arie Vayner (avayner) wrote: > Justin, > > The group number sets the virtual MAC address assigned to that group. > If you have some transparent L2 infrastructure (such as a VPLS domain > you try to transit) this could cause issues, and using different groups > per different VLANs is critical. In most other cases there is no need to > change group numbers between VLANs. > > Take a look here: > http://www.cisco.com/en/US/docs/ios/ipapp/command/reference/iap_s2.html# > wp1073440 > > Another point is that you can use HSRPv2, which extends the group number > to 4096: > http://www.cisco.com/en/US/docs/ios/ipapp/command/reference/iap_s3.html# > wp1063204 > > Arie > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Justin Shore > Sent: Monday, December 22, 2008 21:19 > To: 'Cisco-nsp' > Subject: [c-nsp] Sharing HSRP group numbers across multiple HSRP > instances > > I have a situation in which I'm wondering if I can use the same HSRP > group number for multiple SVIs on a pair of 7600s. The VLANs all > perform similar functions in groups of 3; outside of FWSM contexts, > inside of FWSM context, SVI for terminating client IPSec VPNs. Ie, each > > customer has 3 VLANs that perform these functions. I have multiple > customers and each has 3 VLANs in VRFs (where applicable) on my 7600s > carved out for these specific functions. > > Can I use the same HSRP group for each of the individual 3 VLANs across > multiple customers? ie: > > Customer VLAN Purpose > ------------------------------- > 1 1501 Outside > 1 1601 Inside > 1 1701 CVPN > 2 1502 Outside > 2 1602 Inside > 2 1702 CVPN > 3 1503 Outside > 3 1603 Inside > 3 1703 CVPN > > Purpose HSRP Group > --------------------------- > FWSM outside 100 > FWSM inside 101 > CVPN 102 > > VLANs 1501-1503 get group 100, 1601-1603 get group 101, 1701-1703 get > group 102. Each customer VLAN performing that specific role shares that > > HSRP group #. That's worded better. All VLANs share the same L2 > infrastructure (actually they never leave the 7600s). > > Is this doable or should I just use HSRPv2 and one of the 4096 group #s > available to me? Would sharing group #s result in few HSRP hellos send > and processed, thus lower RP overhead? > > Just curious. Thanks > Justin > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
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