OSPF - network command

[kevwilson6411]

This question has probably been asked many times before.

When typing a the network command in ospf ie network 10.0.0.1 0.0.0.0 area 0

I gather that the wildcard mask will associate all interfaces in the wildcard mask range with OSPF area 0. However is this like eirgp and all those attached ip addresses that match the network command will be advertised from that router?

Hope that makes sense.

Regards

Kev

[paul driver]

Hello kevin

Your syntax will advertise just that specific interface, to advertise all interfaces on that router you can use:

router ospf xx

network 0.0.0.0 0.0.0.0 area 0

res

Paul

Please don't forget to rate this post if it has been helpful.

[kevwilson6411]

Further Question

Will this advertise the interface to gain a neighbor?

What is confusing to me is that in EIGRP the network command does to things.

1. Advertises the network to its neighbors

2. All the interfaces in the network range to participate in sending hellos, to gain a neighbor.

What does the network command in OSPF do?

Is it just

1. All the interfaces in the network range to participate in sending hellos, to gain a neighbor.

Does it need to advertise the networks to its neighbours like eigrp, or does it use LSU / LSA to all this within that area?

Regards

[Reza Sharifi]

It is the same.  When you add the command under the OSPF, it advertises the networks to neighbors to gain neighbor(s).  If the neighbor router is not configured, then there will be no neighbor adjacency, but the network will be advertise to OSPF data base.

HTH

[paul driver]

Hello,

The adjacency will be formed from the most stable interface available, so ospf will choose a router id for this neighbor via the highest loopback ip address on the router, and if no loopback is available then it will choose the highest interface ip.

Bear in mind that a physical connect between the two routers is required and these interfaces will not necessary become the router id for the ospf adjacency.

Also, all interfaces as stated will be advertised in ospf with the above command.

hope this makes sense?

res

Paul

Please don't forget to rate this post if it has been helpful.

[kevwilson6411]

Many thanks,

regards

Kev

[paul driver]

Hello Kevin

Please don't forget to rate any posts that have been helpful.

[Joseph W. Doherty]

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Posting

To your original question, the OSPF network statement looks for interface IPs (just the IP; interface's subnet mask is ignored) to match the network statement's IP and mask; much like an ACL.  When a matching interface IP is found its interface joins the matching OSPF process and the interface's corresponding network joins the OSPF database.  This is the primary purpose of the network statement; identification of OSPF interfaces.

Once an interface has been included into the OSPF process, the interface isn't just a network destination to be advertised.

On this (your) question, interfaces that have been matched are candidates for forming neighbors, but there's much that has to agree between neighbors before they will form an adjacency.  For example, interface has to be non-passive, and many OSPF variables must agree (same area, same kind of area, passwords [if defined], etc.)

Once an OSPF adjacency is formed, the neigbors will sync up their corresponding databases.

Once the local OSPF process has what it believes to be a current database, it will populate the route table with what it believes to be the best path to different destinations.

[kevwilson6411]

Joseph,

Great explination

Thanks

Kev