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HSRP+Many VLANs = Wasted IP Space?

I have a situation where I have 2x 2800s providing LAN connectivity to multiple floors in a building. Each tenant on each floor receives their own VLAN - some floors have 3-4 tenants, others have 40+; there are ~110 VLANs total.

These are all trunked on 3500-24XLs to the primary 2800's g0/0. That is working fine.

I am attempting to add the second 2800 into the mix to make things redundant, and the obvious answer is HSRP. Problem is that every HSRP virtual interface requires 3 IP addresses - one virtual, one on 2800A and one on 2800B.

Overwhelmingly we issue /30s and then, if needed, route a /28 or /29 to them. If we use the standard HSRP model, we have to renumber, for which we do not have the ip space - we go from using /30s to /29s and wasting a LOT of addresses.

I have attempted to use 10.10.10.x subnet addresses on the physical subinterfaces on 2800A & 2800B, then putting the public IP on the virtual HSRP int (different subnets for real/virt). Problem is that the HSRP IPs do not show up in the routing table. This makes sense, considering the documentation stating that all three IP addresses must be in the same subnet.

Any way around this? We already have WAN connectivity handled, but this has us tied up. Renumbering is extremely time consuming and will most definitely put us in an IP crunch. Any solutions or recommendations will be most welcome.




Re: HSRP+Many VLANs = Wasted IP Space?

For the IP address space, there is no way to use less IP address for HSRP.

You may need to enable the NAT in 2800 then reassign the IP address subnet to all users. Otherwise, there is no way to borrow IP subnet from any locations. Prepare a good IP address plan will solve the problem.

Hope this helps.

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