configure HSRP on two routers and do layer 3 IP routing on a core switch

[eash]

Hi ,

Please help me configuration of HSRP with 3750 switch and two routers for internet backup.

Regards,

Easwar

[Konstantin Dunaev]

what is the goal for HSRP? to connect 3750 and to other routers? I'd suggest to use a dynamic routing instead.

[smitesh kharecha]

Hi,

You need to track the internet link on your primary router for your requirement.

However, I would suggest to load balance between two links and not just use one link at a time, as you would be paying for your secondary link; even though when you would be very rarely using that.

HTH,

Smitesh

[eash]

Hi Konstantin,

Service would not allow us to configure any sort of dynamic routing.

the setup is as follows

Internet

|          |

|          |

|          |

R1     R2

\          /

\       /

   \   /

Switch(3750)

Regards,

Easwar  

[Konstantin Dunaev]

what do you mean "service"?

you can configure HSRP as Smitesh suggested, but from the experiebce I can say that all kinf of  tracking interface is not very reliable.

[Kishore Chennupati]

Hi Konstantin,

I beg to differ here with you. HSRP is widely deployed in such scenarios in small to medium scale enterprise netwrk deployments. Can you shed some light where you didnt find it particularly unreliable?. please relate your answer to similar scenario and not any other.

I agree that dynamic routing also is good and works well. I guess it depends on what you network requirements are. For eg: in this case Eshwar's company doesnt want dynamic routing protocol for whatever reasons so he has to go for HSRP.

HTH

Kishore

[Konstantin Dunaev]

I aggree that HSRP is widly deployed, but mainly in access layer, to get the end devices reliable access to the network. Of course if the dynamic routing protocol is not possible for some reasons - HSRP is a good option.

in short: HSRP provides only, let say one-way, communication, one can configure a tracking and adjust a HSRP prio based on reachability of next hop to switch the traffic to the backup link, the opposite side doesn't know that it should use alternative way. But in you answer you've already gave  some tips what and how can one use HSRP in such scenario.

I've just suggested to think about dynamic routing, because from my point of view it's more suitable for such scenarios.

[Kishore Chennupati]

Hi Eshwar,

Lets assume you want R1 as primary and R2 as backup. In HSRP you use something called priority to establish which one is primary router and which is backup. The maximum priority is 255 and default is 100 so you can set the priority on the R1 router to say 120 and it will be the primary path for the traffic going outbound.

Below links should help you more. Let me know if you need more help with this.

http://www.ciscopress.com/articles/article.asp?p=766858&seqNum=4

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080093f2c.shtml

Now, you are takling about internet here so have you got BGP configured with correct Local preference etc so that you have a primary back up scenario. Also have you got iBGP configured between R1 and R2 as well?

Because to fully configure a primary/ backup path you need to make sure you have the right config in terms of HSRP and BGP as well otherwise assymetric routing will occurs causing performance issues.

HTH

Kishore

[Kishore Chennupati]

Hi Eashwer,

How did you go with this? Did you deploy the solution yet?

Kishore