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New Member

DDR Backups with Floating Static routers

I am setting up DDR backups and have a question about errors. We have these two sites that have cronic problems with thier T1's. Although the T1 doesn't go down hard, it starts to take so many CRC errors that traffic degrades severly. I am afraid the RIP2 updates will still cross the link since it still passes traffic and never trigger the Dialer.

Can this be a problem and is there a way around it?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: DDR Backups with Floating Static routers

Edwin

You seem to have understood Denny's question to be about the possibility of RIP triggering the dialer. I understand something different in his question. I believe that the question is based on an assumption that when the primary circuit becomes degraded that he would like the backup to kick in and questions if the degraded circuit will still pass RIP updates which will prevent the dialer from starting. I believe that the answer is that probably the degraded circuit will pass enough RIP updates that the dialer will not start.

If my understanding of the basic assumption is correct it is slightly different from the typical environment of DDR wich is intended to initiate when the primary circuit fails, not just is degraded. In the traditional implementation I do not believe that there is a way to get it to start when the circuit is degraded but still operational. I have not used it and can not say for sure that it would work, but I believe that a new feature in IOS may allow Denny to achieve the initiation of DDR when the circuit is degraded. The new feature is Enhanced Object Tracking. This feature tracks reachability of remote objects, and if I understand it correctly it allows you to set a threshold where it will take action. So you might be able to configure it to ping some address and if x% of pings fail it can remove the route from the table which could trigger DDR.

This link is a good place to start to learn about Enhanced Object Tracking:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541be.html

HTH

Rick

4 REPLIES

Re: DDR Backups with Floating Static routers

Hi

If your seeing CRC errors in your T1 links would always suggest to get the reliability of the same with your Telco by taking a loop from their end.

in most of the case that would solve the probs in the first place.

about RIP2 updates dialing out your dialer you can block the rip packets in triggering the dialer by allowing only the particular interesting traffic to dial out using the dialer-list command in conjuntion with the ACL matching the source/destination networks.

regds

Hall of Fame Super Silver

Re: DDR Backups with Floating Static routers

Edwin

You seem to have understood Denny's question to be about the possibility of RIP triggering the dialer. I understand something different in his question. I believe that the question is based on an assumption that when the primary circuit becomes degraded that he would like the backup to kick in and questions if the degraded circuit will still pass RIP updates which will prevent the dialer from starting. I believe that the answer is that probably the degraded circuit will pass enough RIP updates that the dialer will not start.

If my understanding of the basic assumption is correct it is slightly different from the typical environment of DDR wich is intended to initiate when the primary circuit fails, not just is degraded. In the traditional implementation I do not believe that there is a way to get it to start when the circuit is degraded but still operational. I have not used it and can not say for sure that it would work, but I believe that a new feature in IOS may allow Denny to achieve the initiation of DDR when the circuit is degraded. The new feature is Enhanced Object Tracking. This feature tracks reachability of remote objects, and if I understand it correctly it allows you to set a threshold where it will take action. So you might be able to configure it to ping some address and if x% of pings fail it can remove the route from the table which could trigger DDR.

This link is a good place to start to learn about Enhanced Object Tracking:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541be.html

HTH

Rick

New Member

Re: DDR Backups with Floating Static routers

Rick,

Thank you for your response. This is exactly what I was looking for.

Re: DDR Backups with Floating Static routers

hi rick

Thts simply kool & gr8 :-).

From next time on i will make myself to think out of box solutions too..

regds

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