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michaelwarner
Beginner

OSPF Network Mask?

Hello,

I am configuring OSPF on our MPLS routers in order to advertise our internal networks out to BGP (via the redistribute command).  I am a bit confused on the proper syntax of the OSPF network command for our situation.  The normal setup is that the MPLS router has a link to the core router for that site via a /24 network.  That network is part of a /21 range for the entire site, so the networks would look something like this:

MPLS link to core: 192.168.1.0/24

Core networks: 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24, etc.

Would the best option for  OSPF network statements be:

MPLS router: network 192.168.1.0 0.0.0.255

Core router: network 192.168.1.0 0.0.7.255

or

MPLS router: network 192.168.1.0 0.0.7.255

Core router: network 192.168.1.0 0.0.7.255

or

MPLS router: network 192.168.1.0 0.0.0.255

Core router: network 192.168.1.0 0.0.0.255, network 192.168.2.0 0.0.0.255, network 192.168.3.0

Thanks,

Mike

1 ACCEPTED SOLUTION

Accepted Solutions

Hi,

I would enable OSPF just in the interfaces that are going to speak this protocol, for example:

net 192.168.1.1 0.0.0.0 area 0

net 192.168.2.1 0.0.0.0 area 0

net 192.168.3.1 0.0.0.0 area 0

Best Regards,

Jose.

View solution in original post

8 REPLIES 8
Muhammad Thanveer
Contributor

Can you please make a simple diagram for your network.

basically your network command for 192.168.1.0 0.0.0.7.255 makes to check the networks 192.168.0.0 to 192.168.6.0

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."

This may be useful to you

http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cospf.html#wp4937

Please rate helpful posts.

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."

Hello Muhammad,

I have looked at Cisco's OSPF documentation, but still have not found a clear answer for this question.  Apparently the network statements define the network range for all OSPF interfaces on a particular device.  I guess my question is if the wildcards on the MPLS router and core need to match?  Here is a diagram of what I am trying to do:

By the network diagram you have shared

I understood that

you have a mpls router which made a ospf adjacency with the network 192.168.1.0 (in Area 0) with the core device at site 1

and all other routers has made adjacency with core device at site1 with their respective networks

and core has summarised the network and made adjacency with all the respective routers.

Q1) Can you see all the routes which are under core device when you issue a command show ip route ospf by O as their flag.

If your answer is yes we wll proceed furthur, now if you see all the routes then you have redistributed them in to bgp and all the bgp routes in to ospf at site 1. Now when you issue the commands you would be able to see the bgp routesre which are distributed as OE1 or OE2 routes

Q2) Are you able to see them.

If yes then their is no issue at site 1.

Now if you go to site 2

Can you see all the routes which are comming from the BGP neighbor.

If yes you can redistribute them in to ospf adjacent router. and you would be able to see them as OE1 or OE2 routes.

If this explanation doesn't serve your need give me the exact network diagram, I will make a test lab and share you with the configs.

Please Rate the helpful posts.

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."

It looks like all of the networks are being advertised with the exception of a couple of networks at different sites.  The only thing I can find that stands out in the config is that the internal networks are represented as individual /24 nets in the OSPF config on the core routers.  I will try summarizing these sometime this week to see if it fixes the issue.

Hi,

I would enable OSPF just in the interfaces that are going to speak this protocol, for example:

net 192.168.1.1 0.0.0.0 area 0

net 192.168.2.1 0.0.0.0 area 0

net 192.168.3.1 0.0.0.0 area 0

Best Regards,

Jose.

View solution in original post

Thanks Jose.  After all I have read on the subject, this seems to be the safest way to go.

Mike

It's time to forget the network command and use the

ip ospf 1 area 0

interface command.