Route Redistribution

[NETAD]

Hello, we are adding a new remote site with 2 MPLS circuits and 2 ASR's at the DC and each will have its own MPLS circuit. The remote site is Meraki so we have to use OSPF. In our Data Center we have EIGRP running. I'm looking for advise onto where should I redistribute. Should I redistribute on the ASRs and block the routes from looping back in or should I redistribute on the Core switch. 

[Giuseppe Larosa · Accepted solution]

Hello @NETAD ,

redistributing on the two ASR nodes would require the use of route-maps to set route-tags unless you can send in OSPF a simple default route to the remote site to avoid mutual redistribution.This can be acceptable if internet access of remote site is via DC site.

On the other hand if the core device is only one device at least at logical level (using VSS or SVL) it would be a better place to perform mutual redistribution with no risks.

OSPF requires the subnets keyword to avoid automatic summarization when redistributing EIGRP into OSPF.

EIGRP requires that a seed metric made of 5 components to be set either as a default-metric or in the route-map used for redistrution to be able to redistribute OSPF routes into EIGRP routing domain.

Hope to help

Giuseppe

[NETAD]

Thanks. So if I perform the redistribution on the Core (and it is a C9500 stackwise virtual setup) do I still have to tag the routes and block the tag inbound on the ASRs? 

[ngkin2010 · Accepted solution]

As @Giuseppe Larosa said, if your core switch is the only one device (logically) doing mutual redistribution, then you don't need to tag the route, and block the tag inbound.

To add one more note, route tag is one of the option/trick to prevent routing loop (if you got any EIGRP external route in DC). You may also adjust the administrative distance of OSPF external route, such that it become higher than EIGRP external (170).