ospf point to multipoint

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Aug 26th, 2007
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hi, i have 2 routers on a frame-relay network, i ran ospf on them with network type point-to-multipoint, now when i check the routing table on both routers i can see other serial interface ip with /32 mask which is directly connected to the other router, so i checked cisco and it said that it happens

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9ea.shtml

but i dont understand that why it is happening ?? and if i want to prevent it can i do it ??


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Joseph W. Doherty Sun, 08/26/2007 - 11:27
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I don't recall if this would fix your concern about seeing the /32, but you might try using point-to-point if you running a PVC only between your two routers. Helps avoid some NBMA issues. See the OSPF design guide, start with "Adjacencies on Non-Broadcast Multi-Access (NBMA) Networks " in: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t24

Edison Ortiz Sun, 08/26/2007 - 12:05
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It's working as designed. On a NBMA network, the router needs to know about its neighbor in order to send the hello packets.


NBMA network, by default, is non-broadcast and when OSPF is configured on the interface, you must also configure the neighbors under the OSPF process.


If you change the OSPF network as point-to-multipoint, the protocol will announce its interface as a stub network to its neighbors for reachability. Removing this function will break the OSPF adjacency.


HTH,




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