Ignoring routing updates based on tag value

Cisco supports route tagging for most IGP's

BGP uses communities to mark and to classify routes see Application of BGP Communities

for IS-IS see for RIP IPv6 see

for OSPF we should be more precise in describing the feature - a route map can be used to prevent OSPF routes from being added to the routing table. This filtering happens at the moment when OSPF is installing the route in the routing table. So the route is "blocked" only on the router that has the filtering configured Received LSA's are still added to the OSPF database and LSA flooding continues as normal.

This is entirely correct. Additionally when routes are redistributed between routing protocols, including OSPF, the route is blocked from all routers participating in the particular "routing domain".

[snip]

see

for RIP IPv6 see The documentation does indeed say how to tag IS-IS and RIPv6 routes -- but offers no solution for the problem of ignoring routes carrying a specific tag, which is what I want to do. Apparently the only place where tags can be used to control router behavior is in redistribution.

Yes. Preventing the route from being added to the routing table is enough for my purposes.

Best regards, Tiago

your problem may be the type of routes.

OSPF relies on all routers in an area having identical LSDB contents - the protocol breaks if not. This affects "internal" OSPF routes.

external routes are those carried that came from other sources and those dont have the same restrictions.

So all the filters can do is affect what gets translated into an active rouete - see the other posts.

With OSPF it is much simpler to filter the routes at source and stop them getting into the OSPF process in the 1st place.