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HSRP using VLAN with different network subnet masks

I have configured a few VLANs uplinked to 2 x 4506 L2/L3 devices. All VLANs,

except one, is a different 10.1.n.n/24 network and the 4506's are configured for HSRP for each VLAN. ( .1 virtual, .2, .3). As well, OSFP has the network defined.

HSRP tests between the VLANs using SHUTDOWN worked well.

Then I added a VLAN to the configuration. HSRP was defined on the 2x4506 switches as for teh other VLANs. The VLAN was not added to OSPF.

Connectivity to/from these two network groups was confirmed.

However, HSRP tests were strange. If the ping is sent from to a device on any VLAN and the active or router interface is shutdown, recovery either does not happen at all, or every second ping times out.


Is there a problem with OSPG and HSRP together?

Should I add this new network to OSPF?


Re: HSRP using VLAN with different network subnet masks

At the first look, it looks really strange but What i can visualize is that your ping requests are reaching your destination but the replies somehow come in two direction (May be the routing table has 2 paths for the return path) and one of the reply dont reach ping originator because one of the HSRP interface is shutdown.

I would better check the routing table for any multiple paths in both directions


Re: HSRP using VLAN with different network subnet masks

Indeed without more info on the topology I would guess that (some of) the return traffic ends up on the switch where the vlan interface is shutdown and this switch does not have a route to

Possible solutions:

- add to ospf (and use passive-interface if you do not want to route over this vlan)

- redistribute connected in ospf

- add a static route to via the other switch (it will be overridden by the connected route as long as the vlan interface is up)



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