Ignoring routing updates based on tag value
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Posted by charset on May 27, 2008, 5:14 pm
Please log in for more thread options I am trying to configure Cisco IOS so as to ignore updates received through a particular routing process based on the tag they carry. So far, I found out about the distribute-list command used in router configuration mode, e.g.: router ospf 100 distribute-list route-map foo in ! route-map foo deny 10 match tag 42 ! The above commands, in my understanding, ignore all routing updates received via OSPF instance 100 carrying a tag with value 42. However, the documentation for IOS release 12.4T says that the route-map clause of the distribute-list command is only available for the OSPF and EIGRP routing protocols. Do you know of any way to filter updates based on the tag value in routing protocols other than these? Thanks in advance for your help. Best regards, Tiago | |||||||||||||
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Posted by Merv on May 28, 2008, 5:24 am
Please log in for more thread options Cisco supports route tagging for most IGP's BGP uses communities to mark and to classify routes see Application of BGP Communities http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_6-2/bgp_communities.html for IS-IS see http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gtisitag.html#wp1041820 for RIP IPv6 see http://www.cisco.com/en/US/docs/ios/12_2t/ipv6/SA_ripv6.html#wp1051864 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. | |||||||||||||
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Posted by on May 28, 2008, 6:56 am
Please log in for more thread options > > I am trying to configure Cisco IOS so as to ignore updates received
> > through a particular routing process based on the tag they carry. So > > far, I found out about the distribute-list command used in router > > configuration mode, e.g.: > 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". | |||||||||||||
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Posted by charset on May 28, 2008, 11:15 am
Please log in for more thread options > > I am trying to configure Cisco IOS so as to ignore updates received
[snip]
> > through a particular routing process based on the tag they carry. So > > far, I found out about the distribute-list command used in router > > configuration mode, e.g.: > for IS-IS
seehttp://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gtisit...
> for RIP IPv6
seehttp://www.cisco.com/en/US/docs/ios/12_2t/ipv6/SA_ripv6.html#wp1051864
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. > 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. Yes. Preventing the route from being added to the routing table is enough for my purposes. Best regards, Tiago | |||||||||||||
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> through a particular routing process based on the tag they carry. So
> far, I found out about the distribute-list command used in router
> configuration mode, e.g.: