How can I get HSRP (or VRRP) to work with separated L3 switches

[bnace]

I have a distribution network that uses multiple L3 switches that route end points using OSPF routing protocol. The various L3 switches are connected using /30 point to point subnets. I can only get HSRP (or VRRP ) to work with adjacent L3 switches and then only if a L2 802.1q trunk connects the two switches.

How can I eliminate the trunk connection?

[Jon Marshall]

For HSRP and VRRP to work you need a L2 path between your switches so if you have multiple vlans you need a trunk. 

If your switches are only interconnected with L3 links then you can’t use either. 

Jon

[bnace]

Let me clarify the topology a little more. Two of the L3 switches are routable. The desired VLANs are created as well as SVC Vlan Interfaces. If a L2 switch connected Uplink and downlink via 802.1q to each of the switches and the l2 switch has switchports configured for the desired vlans, then edge host can communicate to any routable IP in the L3 switches routing table.

Let's for purpose of argument say one of the vlans is 301. If the L3 interface has an SVC interface for VLan301 and an IP is assigned to it on both L3 switches, then a L2 connection exists between the two end point L3 switch and the intermediate L2 switch. However; HSRP will not advertise through the 1 hop trunk. It will advertise over a direct connected trunk (no intermediate switch).
For example here's a log of two standby groups, 1 with only a direct connection (Grp 2) and the other with intermediate L2 switches (Grp 4)

*Sep 20 03:39:15.251: HSRP: Vl301 Grp 4 Hello out 10.9.30.158 Active pri 95 vIP 10.9.30.129
*Sep 20 03:39:16.104: HSRP: Vl61 Grp 2 Hello in 10.9.6.157 Active pri 110 vIP 10.9.6.129
*Sep 20 03:39:17.051: HSRP: Vl61 Grp 2 Hello out 10.9.6.158 Standby pri 95 vIP 10.9.6.129
*Sep 20 03:39:17.820: HSRP: Vl301 Grp 4 Hello out 10.9.30.158 Active pri 95 vI10.9.30.129
*Sep 20 03:39:18.694: HSRP: Vl61 Grp 2 Hello in 10.9.6.157 Active pri 110 vIP 10.9.6.129
*Sep 20 03:39:19.623: HSRP: Vl61 Grp 2 Hello out 10.9.6.158 Standby pri 95 vIP 10.9.6.129

Does anyone know how to get the HSRP advertisements through the L2 switch trunk? Without doing this I end up with both vIP being active which messes up the routing of traffic inbound from the L2 switch.

SWA#standn by brie
P indicates configured to preempt.
|
Interface Grp Pri P State Active Standby Virtual IP
Vl61 2 110 P Active local 10.9.6.158 10.9.6.129
Vl301 4 110 P Active local unknown 10.9.30.129
SWA#
SWB #standn by brie
P indicates configured to preempt.
|
Interface Grp Pri P State Active Standby Virtual IP
Vl61 2 110 P Active local 10.9.6.157 10.9.6.129
Vl301 4 110 P Active local unknown 10.9.30.129
SWB#

[Jon Marshall]

You only need a L2 path not a direct connection between your L3 switches. 

Check each switch and make sure you have added the vlan to vlan database and it is allowed on the trunk links. 

Jon

[bnace]

There is a L2 connection, just not a dedicated one. The series of L2 switches interconnect via an 802.1q trunk to the two L3 endpoints. I’m trying to understand the difference, from an HSRP POV, between a single dedicated trunk connection and a trunk that daisy-chains between a series of switches.

[Jon Marshall]

From HSRP's perspective absolutely no difference at all. 

Jon

[bnace]

That’s what I thought! When I run ‘debug standby packets’ from CLI , I see that the HSRP ‘out’ messages are being dispatched on both L3 switches but no ‘in’ packets are received. 

Do do I need some special cef setting on the L2 switches?

[bnace]

That’s what I thought! When I run ‘debug standby packets’ from CLI , I see that the HSRP ‘out’ messages are being dispatched on both L3 switches but no ‘in’ packets are received. 

Do do I need some special CEF setting on the L2 switches?

[Jon Marshall]

Did you do the checks I suggested before ? 

If so the only other thing I can think of is IGMP snooping which should not affect HSRP packets but I have seen it do so at least in lab setups. 

Jon

[bnace]

I don’t think I have IGMP snooping on. Do you recommend it be on or disabled?

[Jon Marshall]

It is usually on by default depending on your switch models. 

Check the vlan databases and the trunk links on all your switches. 

Jon

[bnace]

Did all this with no change. Vlan database OK. 

Still looking for ideas.

[bnace]

Yes, to answer your question about vans and trunks. That was one of the first thing I checked. Also verified that same native vlan is used in each L2 switch and that its local interface is ‘up’