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New Member

OSPF over NBMA - how to add redundancy?

Good day.


Please take a look at Pic.


R1 and R2 are HQ routers. R3, R4, R5 are branch routers.

HQ routers have FR PVSs to every other router, branch routers have PVCs only to HQ routers. Nevertheless possibility of accessing resources in one branch from another must be ensured.


At a glance it seems that it will be good solution for this topology to use OSPF network type broadcast and police that R1 will become DR and R2 BDR, and add static FR mappings between R3, R4 and R5. But consider possibility of broken communication for e.g. between R5 and R1. This action will not trigger R2 to become DR (R1 is still alive) so R5 will still has working path to HQ but will not receive any OSPF LSAs, cos it hasn`t connection to DR.

Ok, so from that i can made conclusion that electing DR/BDR on FR topologies with redundant nodes at HQ is not desired (BTW can anyone give me example where it really required?).

From here i had changed ospf network type to point-to-multipoint and voilà - R5 now  received LSAs and have converged OSPF database... but R5 loss access to other branches. Why? Cos it have static FR mapping to other branches goes through R1, but  connection to R1 is lost.  How to handle whith it? The only answer i see - use of full mesh, but constraints are that partial mesh exists.


Can anyone give a tip here?


Hey,Lets add another static


Lets add another static mapping to access other sites via R2, what say..??




New Member

Good day.But its impossible,

Good day.

But its impossible, isn`t it?

%Address already in map