Which failover method would fit best?

[NiclasAnd]

Hi,

I have been given a task, where I need to create a failover setup from a 1800 Cisco router to a LAN network 2 hobs away (see topology).

The reason I have been given this task is because the wireless links are not so realiably, but necessary.

I'm thinking of doing this failover task with IP SLA on the routers fiber 1 and fiber 2 link, so when/if one off the links goes down, it instantly chooses the other link.

I have also been thinking about implementing STP instead, and replace the router with a switch, but i'm not sure exactly how to implement it.

These are only some thoughts I have been given this task, but I'm very open for other ideas.

Unfortunately I'm not able to test anything, as we are still waiting for the fiber lines, but I want to be prepared as much as possible.

Regards,

Niclas

[blau grana]

Hello Niclas,

I got some ideas, but to be sure they can be used, could you specify what types of router and switches are you using?

If S1 & S2 would be L3 switches, you can run HSRP/VRRP between them so if primary wireless link will fail, backup will be used. If you configure more groups, you can load balance traffic and still use one wireless link as backup for another and vice versa.

Between on fibre link interfaces you will run udld aggresive, so if fibre link will fail, interface will go down. Interface status will be tracked by HSRP, so if switch (S1,S2) detects that fibre interface is down, local switch can not be used as gateway anymore and advertise this info to HSRP/VRRP peer.

Best Regards

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[NiclasAnd]

Hi Blau Grana,

Thank you for the reply.

I will be using L3 switches, so HSRP will be supported.

If I decide to use HSRP, how can I configure the tracking?

The wireless devices which are connected to the S1 and S2 are both an Ubnt Nanostation M5 and therefore it's a separate device, which is why the tracked port will not shutdown if I use tracking on a port.

I can see that it's possible to track an object, but how does that work?

Regards,

Niclas

[blau grana]

Hello Niclas,

If I decide to use HSRP, how can I configure the tracking? The wireless devices which are connected to the S1 and S2 are both an Ubnt Nanostation M5 and therefore it's a separate device, which is why the tracked port will not shutdown if I use tracking on a port. 

HSRP will be configured on switches S1 and S2. Thanks to udld aggresive running on fiber links [R1<=>S1 and R1<=>S2] switch port will go down if link will fail. HSRP will track this uplink port toward R1. If uplink port is down => switch has not working uplink link, no connection to gateway => HSRP will not provide gateway service to hosts on S3.

S1 and S2 will run HSRP to communicate together, hellos will be send via both wireless links and S3. So if primary fiber link fail, HSRP will advertise this change to HSRP peer which will preempt to become new gateway.

If both fibre links are working, but primary wireless link will fail, no HSRP hellos will be sent/received, so HSRP backup will preempt and become new gateway.

If you have any further questions about design or you need any help with configuration, just let us know

Best Regards

Please rate all helpful posts and close solved questions

[paul driver]

Hello
as blau stated we need to define how.your topology is setup

ip sla is an a poasible option and that could be used with EEM

also a simple backup command could be used

all depends on your topology!

res
Paul


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[Collin Clark]

This may seem a little bit overkill but because of unreliable links I think a good option would be to use PfR. Here's a link explaining what it does and how it can overcome less than reliable links.

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/ps8787/product_data_sheet0900aecd806c4ee4.html

Hope it helps.