Routing between three ML-Switches (two of them in an HSRP Group)

[Jochen Reinecke]

Hello guys,

i like to route between some Multilayer-Switches in our Company. Two of them are oparing in an HSRP-Group for some Client-VLANs. So These Switches only have L2-Connections between them, no routed-ports.

I want to connect a third Multilayer-Switch with both, the active and the standby unit. I like to configure static Routing with load sharing and fault tolerance. So i've configured two Transfer Networks to the hsrp Switches. The default route on this (third) side is clear, but how can i Setup Routing on the hsrp Switches to reach the Networks behind the third device over two ways?

Any idea? I belive it's a simple solution but i was thinking about a few days and didn't catch the goal. The topology is shown graphically in the attachment.

Thanks and Regards,

Jochen

[Reza Sharifi]

Hi,

In order for HSRP to work correctly, the first thing you need to do is to connect each 2960 access switch to both core switches (10.222.10.2 and 3) if not, there is really no need for HSRP as the access switches connect to one device only and does not provide gateway redundancy for the end devices. Once that is correct, you can use static route from the core to the third switch to provide access to vlans 10 and 30 so they can communicate.

on the core switches 

ip route 10.221.30.0 255.0.0.0 10.220.10.2

on the 3rd switch 

ip route 10.221.10.0 255.0.0.0 10.220.10.1

HTH

[Jochen Reinecke]

Hi Reza,

i am agree with your HSRP considerations. But im not sure about Routing on core-switches as you discribed.

If i only use 10.220.10.2 as next hop, how schould traffic be load balanced via 10.220.20.2 an how does the other HSRP node schould know about These Transfer Network if Primary router Fails? It isn't directly connected.

Thanks and Regards,

Jochen

[Reza Sharifi]

Hi,

If i only use 10.220.10.2 as next hop, how schould traffic be load balanced via 10.220.20.2 an how does the other HSRP node schould know about These Transfer Network if Primary router Fails? It isn't directly connected.

So, the traffic will not be load balanced.

The outbound traffic (vlan 10) will always go through the HSRP active switch.  So, in your diagram, if the 10.222.10.3 is the active HSRP, all traffic from vlan 10 will traverse that until that router or switch fails and than traffic will use 10.2.  This is all assuming your access switches have connectivity to both core switches.

Is that what you are asking?

HTH

[Jochen Reinecke]

Hi,

i am searching exactly for a solution to forward traffic to SWI3 if the active hsrp router Fails.

Regards,

Jochen

[Reza Sharifi]

Than in that case you really don't need HSRP.  You just need 3 routed (layer-3) links between sw1 and sw2, sw1, 3 and switch 2 and 3.  So, in this case if the link between sw1 and sw3 fails, the traffic will get rerouted through sw2 and up to sw3.

HTH

[Diana Karolina Rojas]

Firts you have to enable routing (ip routing command). For full tolerance you can use Tracking (In the HSRP Switches configuration in links connected to the SW3 switch)

You can configure differents subnets betweens the ports connected to the SW3 switch and the both connected to the HSRP switches, and configure static routing using the next hop configured in the SW3 switch respectively, using the command ip route 10.221.30.0 255.255.255.0 next hop ip address. Also you can enable any dynamic routing protocol.

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Regards,