From: Patrick Aland (paland@gmail.com)
Date: Wed Jun 22 2005 - 08:49:31 GMT-3
NMC has a great paper titled "Forwarding behavior of IGP routing
protocols on the broadcast part I" that talks about some of hte issues
you might run into when using 0.0.0.0 0.0.0.0 in your network
statements instead of being a bit more specific.
http://www.netmasterclass.com/site/member.php?&category=demo&togo=category=Lib
Its under the "Public" PDF files.
On 6/22/05, George Cassels <glcassels3@nc.rr.com> wrote:
> I would say only if the requirements tell you that all IPs must be sent
> with their configured subnet mask would you need to worry about doing
> the ip ospf network point-to-point command. Also I may be off but you
> seem to be saying that the subnet mask in the network command under OSPF
> has to match up with the configured network mask on the interface. If
> that is the case of what you are saying it is not correct. You could
> match 1.X.X.X networks on your router with 1.0.0.0 0.255.255.255. So
> for instance if I have 1.1.1.1/24, 1.2.2.x/24, and 1.3.3.0/24 I could
> match them all with 1.0.0.0 0.255.255.255 area 0. You can also use the
> network command 0.0.0.0 255.255.255.255 which will match every
> configured IP on your router. If I remember right sequence does matter
> so you need to be careful on how exactly you enter the network
> statements. This is because a more general statement like 0.0.0.0
> 255.255.255.255 first will cause the router to never reach the more
> specific statement if they are in different areas.
>
> I did run into a do it lab that had isis running between like R1 and R2
> and ospf running between R2 and R3. What network command you put into
> the ospf network statement would dictate whether R3 had to go through R2
> (the redistributing router) or straight to R1 since they are all on the
> same subnet. I don't remember the exact IPs, but by using the network
> command 172.16.1.0 0.0.0.255 area 0 it allowed R3 to go straight to R1.
> Where as if you use the network command of say 172.16.1.2 0.0.0.0 area 0
> on R2 it would make the next hop IP on R3 R2's address.
>
> Way too much info for your question...Sorry,
> George
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> yesar1@yahoo.com
> Sent: Wednesday, June 22, 2005 12:08 AM
> To: ccielab@groupstudy.com
> Subject: /32 vs /24 for loopback and OSPF
>
> Greetings,
>
> When asked to configure loopback interface as part of OSPF area, when
> should I be
> -using /32 mask for the IP address and subsequently 0.0.0.0 in the ospf
> network statement
>
> (e.g.
> int lo0
> ip add 1.1.1.1 255.255.255.255
> router ospf 0
> network 1.1.1.1 0.0.0.0 area 0.0.0.0)
>
> vs
> -using /24 mask and 0.0.0.255 in the ospf network statement
> (e.g.
> int lo0
> ip add 1.1.1.1 255.255.255.0
> ip ospf network point-to-point
> router ospf 0
> network 1.1.1.1 0.0.0.255 area 0.0.0.0)
>
> Thanks in advance for your help,
>
> Mark
>
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-- --Patrick
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