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sandu_nastas1
Beginner

HSRP and STP Coexistence over a L3 Connexion

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).

design.jpg

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 !

2 REPLIES 2
Abzal
Rising star

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.

Best regards,
Abzal
Hari Vishnu
Beginner

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