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New Member

backup PVCs for frame-relay PVCs


My company runs a backbone that relies on cisco WAN equipment : BPX 8620 , MGX 8850. We deliver frame-relay services to our customers. I want to establish a back-up PVC in case the main PVC goes down. When the main PVC comes back up, the backup goes down. both PVCs shouldn't be up at the same time, so the customer can't do load balancing over them. Assumint the topology is a star, with the customer's branches connect to the headquarters by 2 PVCs. The headquarters has 2 routers for redundancy with the main PVC terminates on the main router and the backup one terminates on the backup router. The 2 routers will run HSRP for the workstations behind them. Each branch has one router only.

The thing is: i want the backup PVC to be created on the fly (when the main one goes down), or at least remain inactive till the main PVC goes down. I need this to be controlled from my side and be completely transparent to my customers.

what i'm talking about has nothing to do with Autoroute and SVCs.

Do my equipment support my requirments? i guess some other vendors like NORTEL can support something similar called: shadow PVC.

help me please

Thanks in advance.


New Member

Re: backup PVCs for frame-relay PVCs

Hi !!

My name is Kevin. There is no real way of doing what you want. In the days of StrataCom they had a product called INS which worked with the IGX. Using ISDN, you were able to provide a backup path and DLCI PVC for a remote site if it went down. There is a messy way of doing it on an IGX where you can use job triggers. How this would work is you would set up a job trigger to detect a line failure. This would then trigger off a job (which you create) to delete the existing PVC and re-create a new PVC down the alternate path. Since you are using BPX's and MGX's i assume your frame relay connections are terminating on an FRSM in the MGX. The problem is you cannot create jobs on the MGX therefore this will not work in your scenario. A customer of mine rquires a similar solution, but they use IGX nodes. I am working on a solution for them where we will use ISDN. How this works is we will have a router connected to each of the IGX's running frame relay switching, with a PRI ISDN interface connected to the Telco. At the remote customer site, they will have a router with a normal serial connection connected to the IGX with a single PVC. If the Telco line goes down, it will trigger an ISDN call into the router directly connected to the IGX, at the same time it will trigger via a job to delete or down the existing PVC and re-create a new one to terminate on the router configured for frame relay switching. In theory it shold work but we may have to get clever with our router configs as we might need to set up tunnels to bind the ISDN call to a specific DLCI. If you like i can keep in contact and let you know how it goes. although i don't know how we could do this on an MGX.


New Member

Re: backup PVCs for frame-relay PVCs


Thanks for your response. But did you hear of the "shadow PVC" feature on NORTEL. I supposed that if NORTEL supports such a thing then CISCO might be doing the same but i don't know how. thank you again


New Member

Re: backup PVCs for frame-relay PVCs

Do you have individual PVCs fail, or are you saying that you have one PVC to one data center router and another PVC to the other data center router? I guess I was trying t guage whether you are trying to have redundant routers, or trying to have both redundant routers and redundant telco paths. In my experience, the more likely scenario would be that the carrier service would require redundancy. Using the same Frame Relay network for both seems to leave you open to carrier outages. I don't have much a solution for you on your specific problem, but it seems you might be better off choosing an alternate medium for your backup path, perhaps an ISDN backup link (maybe too slow?), perhaps a fractional T1 (perhaps too expensive?). Seems having a different medium altogether would be important if fault tolerance is the goal.