Solved: Routing VLAN between two routers

Rickey369 · ‎01-12-2018

Hi All,

I was asked this question in an interview. I have attached the topology.

Question: Switch has 2 VLANS's ( VLAN 10 and VLAN 20). Vlan 10 has to pass through Router R1, Vlan 20 has to pass through Router R2.

If Router R1 fails then Both Vlan's (Vlan 10 and 20) has to pass through R1.

I will be delighted if anyone could help me with this. I am just a CCNA passed out and have just started working in a company.

Regards,

Rickey

Deepak Kumar · ‎01-12-2018

Hi,
It is possible with HSRP protocol.
Here, I am sharing a link to more practice and study.

http://www.routerfreak.com/how-to-configure-hsrp-on-a-cisco-router/

Don't forget to vote, if your issue resolved.

Thanks,
Deepak Kumar

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution if this comment will help you!

View solution in original post

Jon Marshall · ‎01-12-2018

HSRP is per vlan/IP subnet so it would meet the requirements.

Jon

View solution in original post

Joseph W. Doherty · ‎01-12-2018

BTW, not mentioned in the other posts, the links between SW1 and R1 and R2 would need to be trunks, otherwise as the diagram is shown, VLAN 10 would only transit via R1 and VLAN 20 would only transit via R2.

Using trunks wouldn't be the only solution. You could also have one line per VLAN from the switch to each of R1 and R2. The important thing, is to have HSRP work, both R1 and R2 need an interface in those VLANs.

What about the converse? I.e. HSRP can "select" which router is the primary for each VLAN, but what about traffic returning to VLANs 10 and 20?

If that's also a concern, you would need to insure the "costing" to R3 and R4 is such that R1 is preferred for traffic to VLAN 10 and R2 is preferred for VLAN 20.

View solution in original post

Deepak Kumar · ‎01-12-2018

Hi,
It is possible with HSRP protocol.
Here, I am sharing a link to more practice and study.

http://www.routerfreak.com/how-to-configure-hsrp-on-a-cisco-router/

Don't forget to vote, if your issue resolved.

Thanks,
Deepak Kumar

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution if this comment will help you!

Rickey369 · ‎01-12-2018

Hi Sir,

Thank you for the reply.

In HSRP one router will be active and the other will be in standby. But In this case both router has to forward the Vlan traffic( ie; Vlan 10 through R1 , Vlan 20 through R2). Will HSRP help in this case?

Correct me if I am wrong.

Regards

Rickey

Jon Marshall · ‎01-12-2018

HSRP is per vlan/IP subnet so it would meet the requirements.

Jon

Rickey369 · ‎01-12-2018

Hi Jon,

Thank You so much.

Regards,

Rickey

Joseph W. Doherty · ‎01-12-2018

BTW, not mentioned in the other posts, the links between SW1 and R1 and R2 would need to be trunks, otherwise as the diagram is shown, VLAN 10 would only transit via R1 and VLAN 20 would only transit via R2.

Using trunks wouldn't be the only solution. You could also have one line per VLAN from the switch to each of R1 and R2. The important thing, is to have HSRP work, both R1 and R2 need an interface in those VLANs.

What about the converse? I.e. HSRP can "select" which router is the primary for each VLAN, but what about traffic returning to VLANs 10 and 20?

If that's also a concern, you would need to insure the "costing" to R3 and R4 is such that R1 is preferred for traffic to VLAN 10 and R2 is preferred for VLAN 20.

Rickey369 · ‎01-13-2018

Hi Sir,

Thank you so much for those info

Regards
Rickey