Studying up for my BGP+MPLS exam as part of the CCIP track and was working out some labs on BGP Confederations. We don’t use them at work so they were something that I’ve never experienced. First of all I can’t figure out why anyone would want to use them over route reflectors. A couple things I’ve learned:
To redistribute between MP-BGP (Core) and OSPF (CPE), you must redistribute MP-BGP into OSPF and OSPF into MP-BGP.
Assumptions -
In the PE router, a VRF specific OSPF process needs to be started:
PE01(config)#router ospf 200 vrf Cust_B
PE01(config-router)#redistribute bgp 65000 subnets
Very important to include the subnets option unless you are and will ONLY work with classful networks. You will get a warning that only classful networks will be redistributed if you don’t include it. Chances of only working with classful networks are slim (no use of loopbacks), so probably best practice to always include ’subnets’. In my study material I was told that having a customer use OSPF as their routing protocol was not a good idea as the routers were limited to 32 OSPF processes (28 usable). Just checked Cisco and looks like that has been fixed with IOS 12.3(4)T and higher.
PE01(config-router)#router bgp 65000
PE01(config-router)#address-family ipv4 vrf Cust_B
PE01(config-router-af)redistribute ospf 200 vrf Cust_B
Pretty easy setup, just need to remember the redistribution is bi-directional.
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