[c-nsp] Sharing HSRP group numbers across multiple HSRP instances

[Christian MacNevin]

As far as I'm aware, the group number is irrelevant. You're still getting a
group per vlan, it's just that the identifier only reaches 255. The
configuration is all local to the
VLAN, so i'm not aware of any shared anything except for number *space*.

ie:
int vlan 1
standby group 1
standby ip 1.2.3.4
standby preempt
!
int vlan 2
standby group 1
standby ip 1.2.3.5
standby preempt

Still results in two completely separate calculations and sets of
advertisements, no?



On Mon, Dec 22, 2008 at 11:18 AM, Justin Shore <justin at justinshore.com>wrote:

> 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
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