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New Member

Adding floating static routes for backup

We have to routers servicing our backbone

Router A used to service our backbone connection between our offices. It has our ISDN backup on it as well should connectivity be lost between our offices. The backbone connection has now been moved to router B. The ISDN backup is still on A.

Do I just a route statement on router B to router A with a metric of 240? This would be for the ISDN backup.

Do I have to create any other configs on both routers to make the floating static work?

8 REPLIES

Re: Adding floating static routes for backup

Hi Friend,

All you have to do is add a static route with a higher metric than the prefered one pointing it to the routerB (ISDN router)

eg.. on router B

ip route

ip route 20

HTH, rate if it does

Narayan

New Member

Re: Adding floating static routes for backup

thanks,

will try this and let you know.

Silver

Re: Adding floating static routes for backup

Do you mean both A & B are located at same site ?

I believe the primary path is router A and router B as backup path to remote. If this is the case, you have to carry below modification and considerations:

1) Any routing protocol between A & B ?

2) If there is dynamic routing protocol, the floating static at A should be advertise to B. And there is no floating static at B required. At the same time, you have to add corresponding floating static at remote routers.

3) If it is static route between A & B, it can't be possible to have the fail-over, due to static will not know the remote WAN status.

BTW, I could like to counter propose another solution if my assumption as above is correct.

Enable dynamic routing protocol between A & B, you have to configure HSRP between A & B. Let the HSRP to select which router as out-going path. Enable the residtribute connected at router A routing protocol. If one of the remote site down, the ISDN at router A will be triggered and this dialer interface will be redistributed into the routing protocol then router B will it (router B will be the primary gateway at HSRP to the local users, due to it is primary WAN connection). And add corresponding floating static at remote routers.

Please let me know if this suit for you and I believe there should be some areas to be fine tuned for better design. Hope you understand my idea.

Hope this helps.

New Member

Re: Adding floating static routes for backup

lo Jack,

Router B has connection to our REMOTE OFFICE on it. The ISDN PRI backup is on Router A. This whole setup was initially on Router A. We are moving our backbone off the cust router(Router A) but cannot move the PRI off there. Basically the requirement for me to add a route from B to A should our connection to RO drop. The ISDN backup should then kick in and bring up temp connection.

ip route xxx.xxx.xxx.xxx (mask) (ROUTER A IP) 210

Would this work?

Silver

Re: Adding floating static routes for backup

If my assumption is correct, both A & B are located at same sites and connected via LAN. According to my last response, you must have a dynamic routing protocol between A & B in order to let each other to know the routing status. e.g. if ther primary WAN at B is up, the A should know it, otherwise, the floating static of A will up and trigger the ISDN.

In your case, B is primary connection to remote office, so the floating static should be configured at A (PRI) instead of B. Unless B is a backup or secondary link.

Please correct me if I misunderstood the case.

Hope this helps.

New Member

Re: Adding floating static routes for backup

you are 100% correct with what you are saying. The WAN link to remote office is on router B. The ISDN backup is on router A.

So what you saying is that a simple ip route statement is not going to work?

Re: Adding floating static routes for backup

It would depend on how your network is designed and how the return traffic is forwarded fron the remote end.

Also does all the traffic to RO reaches routerB and none of them goes to routerA with PRI ?

say for eg if both the links from router A and router B are terminating on a single router at the remote office then when the PRI link between the RO & routerB fails router B would forward the packets to router a which can dial the ISDN and reach the other side and the return traffic will also be from the same link.

If this case the floating static route at B would work

HTH, rate if it does

Narayan

Silver

Re: Adding floating static routes for backup

I agreed w/ Narayan that add the floating static at B and point to A will work. But B will always be the default gateway for local user. It was because if the default gateway change to A but A require corresponding route to return the packet to B then the primary WAN (assume part of the RO are still using primary WAN connection at B).

Therefore, I prefer to enable dynamic routing protocl between A & B and enable the floating static at A and point to the RO as next-hop. At these floating static will be redistributed to the dynamic routing protocol and the primary WAN routes will also be included in the dynamic routing protocol. Enable the HSRP at A & B LAN interface for local user GW. In this case, both A & B routing table is sync. and easier to troubleshoot if there is link failure, you just need to check the next-hop of the failure route and know the which path is using.

Hope this helps.

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