ospf network advertising

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Sep 26th, 2008
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Hi all, After just reading a book, I see that if I want to advertise a network on my router, the best thing to do is advertise the full wildcard mask of the interface you want to advertise, then it will advertise the subnet of the interface, so if I have interface ay 192.168.1.1/24 and I add router ospf 1 network 192.168.1.1 0.0.0.0, it will still advertise the 192.168.1.0/24 network, is this correct ?

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Giuseppe Larosa Fri, 09/26/2008 - 07:44
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Hello Carl,

yes it is for this reason that network area commands can be regarded as similar to ACL statements:

the network area command is used to decide on what interface(s) to run the OSPF neighbor machine, the IP subnets associated to these interfaces are advertised.


Hope to help

Giuseppe


Giuseppe Larosa Sat, 09/27/2008 - 09:01
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Hello Carl,

if you want to have a fine control this can be used.

However, in my opinion the better choice is to use a wildcard that matches the ip subnet mask.


There are some specific cases where having used 0.0.0.0 in the network area commands lead to some side effects in the forwarding address field of LSA type 5 (if I remenber correctly).


See the following for an exact explanation of network area command


http://www.cisco.com/en/US/docs/ios/12_0/np1/command/reference/1rospf.html#wp1018719


Hope to help

Giuseppe



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