HSRP and STP Coexistence over a L3 Connexion

[sandu_nastas1]

Hello,

Here's the issue:

There are 2 datacenters (DC1 and DC2) and 1 users site. They are interconnected as following:

- DC1 - DC2 (Layer 2 extension). Needed for clustering and high availability (TRUNK Link)

- UsersSite - DC1 - Layer 3 (VLAN 10) (ACCESS Link)

- UsersSite - DC2 - Layer 3 (the same VLAN 10) (ACCESS Link)

There will be a network core switch on every site (3750 or 4500 - haven't decided yet). So the 3 network cores will be interconnected as explained above. (see image attached).

There will be an HSRP configured between the 2 network cores (DC1 and DC2).

So in order to access a ressource on DC1 - the users site has to send its packets to the gateway (which is the HSRP address on vlan 10 of DC1 and DC2).

THE PROBLEM is that at Layer 2 - there is STP enabled, and there is a loop, between these 3 sites. So, in case if, for example, DC1 is the active core, and STP decided to block the port that connects Users site with DC1 site - IT WON'T WORK.

Could you please tell me how can this design be modified, or what configuration has to be deployed for this to work ?

Any advices will be useful.

Thank You !

[Abzal]

Hi,

Which of them is root bridge for VLAN 10? It should be HSRP active router and HSRP standby secondary root bridge.

Switch on UserSite:

#sh spanning-tree vlan 10

I assume you created on these switches SVI for VLAN 10, ports with access mode VLAN 10?

Hope it will help.

[Hari Vishnu]

Can you please provide bit more clarity on the number of VLANS. From the figure, I could understand that user site Switch have only local VLAN which is connected to Core switch by an L3 link. You would like to configure HSRP under L3 interface / under SVI.

Do you have any other user sites. ?

Hari