From: Xiangling (xianglingzj@gmail.com)
Date: Thu Jan 25 2007 - 20:53:44 ART
Hi, Brain,
May seek advise from you for use P2MP in the exam?
In case the NBMA network is using /24 mask on the hub and spokes. If P2MP
is used and only /32s only, do you think it will be considered correct in
the lab exam in case they ask to :
- Enable OSPF on the certain interface
or
- Ensure full reachability
or
- Inject the network into OSPF area xxx but do not elect DR/BDR
Please advise, thanks.
Regards,
Xiangling
On 1/23/07, Brian Dennis <bdennis@internetworkexpert.com> wrote:
>
> Here is a post I made a few months back on this subject:
>
> The behavior of point-to-multipoint is to advertise each end-point out
> as a /32 and suppress the advertisement of the network itself.
> Point-to-multipoint advertised the end points to overcome possible
> reachability issues between devices that are on the same logical subnet
> but do not have direct communication (i.e. spoke to spoke communication
> in a hub and spoke environment). The OSPF point-to-multipoint and
> loopback network types do not advertise the network itself but advertise
> a host route for each end-point. This is as per the RFC.
>
> If you want to suppress the /32s and advertise only the network, you
> would need to use an OSPF network type other than point-to-multipoint or
> configure the network to be in its own OSPF area. After the network is
> put in its own OSPF area, use the area range command to summarize the
> /32s so other routers only see the summarized route.
>
> HTH,
>
> Brian Dennis, CCIE4 #2210 (R&S/ISP-Dial/Security/SP)
> bdennis@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Direct: 775-745-6404 (Outside the US and Canada)
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> johngibson1541@yahoo.com
> Sent: Monday, January 22, 2007 7:28 PM
> To: ccielab@groupstudy.com
> Subject: ip ospf network point-to-multipoint non-broadcast, result is
> that only /32 routes are advertised out
>
> Did any one have the same surprise ? Or is that my IOS version's bug ?
>
> I know point-to-multipoint adds extra /32 routes to 2 adjacent routers.
> Nothing wrong. Still reachable to every interface. Just strange to me.
>
> But I didn't know when "non-broadcast" is added, ONLY /32 routes are
> advertised out to all other ospf routers.
>
> I once used 12.3(1a) with 2514 just to discover that nssa
> default-information originate doesn't work on that particular version.
>
> Now I use 12.3(17a). Don't know if there is a problem.
>
> John
>
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-- Thanks & Regards, Xiangling |-------------------------| | | \ I Love You All / \ / \___________/
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