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Migrating from MPLS Cell Mode to Frame Mode over ATM

We have a backbone of Cat8540MSR acting as ATM-LSR, and 7206VXR with PA-A3 as edge ATM-LSR. Routing protocol on core is OSPF. Currently MPLS (or tag-switching more precisely) is working in cell mode.

For some reasons related to recurent bug and strange behaviours, we are looking into changing our configuration to be able to work in frame mode only.

The idea would be to create a logical star topology by adding 4 "big routers" to our network (12400 routers attached with OC12 to the Cat8540), and

create ATM pvc starting from the 7206VXR to those 4 routers. Frame mode MPLS would be used on those pvc. This means that the Cat8540 would not be used as ATM-LSR anymore, but just as a regular ATM switch.

Sounds crazy? Any comments on this would be welcome.


Re: Migrating from MPLS Cell Mode to Frame Mode over ATM

I do not think it is worth doing this. If I were you then I would sort out the problems by escalating the issues with CIsco and have them fixed.

Changing over to frame based network, you are going to loose all the benefits of cell mode mpls.

Re: Migrating from MPLS Cell Mode to Frame Mode over ATM


I would state this to be a good idea. If you run MPLS over a PVC it is in fact frame mode MPLS. So my first idea would be to setup PVCs between the PEs and then to enable LDP between them and use the Cat8540 only as ATM switch -> NOT cell mode MPLS. There should be no harm done in case you do not include that into routing. check your LDP neighborship and then go on to enable routing. By that you should be able to move all your traffic to frame mpde MPLS. It requires a full mesh of PVCs between your PEs however ... or you could setup the 12400 as core LSRs.

There should be no problem in following your migration path. Nevertheless: get the Cisco guys to help you anyhow ;-)

Kind regards


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