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Scaling a large Layer 2 network

We have a specific requirement in our railway network implementation to have a long Layer 2 network, 40 stations in a row, 2 switches per station.

All these stations have multiple specific use case wireless access points hanging between them, in series.

Now the train must keep the same IP address while moving across the network, hence the need for a Layer 2 network.

We have been thinking of using RPVST+, with IE4010 switches but looks like it might not scale well across so many switches (40 hops from left to right), especially as we need very fast failover times (ideally within 3 seconds).

VPLS tunnels over MPLS seems like an option, but would raise the cost of equipment and make the config more complicated, not to mention we would need to build specific one to one tunnels depending on who wants to talk to what.

REP was considered, but the wireless access points do not support that, only support RSTP.

Any suggestions to build a scalable, resilient network without the additional costs and complexity of using VPLS? Is it a good idea to run RPVST+ on this network?

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johcurra
Cisco Employee

Have you considered using LISP for this?  If you put the train in the EID space, it can keep it's IP address at every station even though they are different L3 spaces.

It may complicate the design overall, but I think you would get much more stability than having an L2 domain span an 80 switch diameter L2 network.