From: Marius Venter (marius@aict.co.za)
Date: Mon Apr 03 2006 - 05:31:38 GMT-3
Hi all
If you configured R1 and R3 with ip OSPF priority 0 and R3 with ip OSPF
priority 10 and R1 and R3 are configured for NBMA mode, R1 and R3 will not
form an adjacency.
The reason for this is that on any network where there is DR election the
neighbors would only ever talk to DR or BDR. Neither R1 nor R2 will become
neighbors and therefore will not complete the adjacency.
N/A 0 ATTEMPT/DROTHER - 66.162.1.1 Serial1/0
In the previous example R3 and R1 both were set up with IP OSPF Priority 0
and thus will not partake in DR and BDR election thus breaking the NBMA rule
with DR election
You can verify this by setting the ip OSPF priority to 1 on either R1 or R3
and then run the show commands again.
This whole discussion is however based on the assumption made in the first
paragraph.
Hope this will shed some light on the topic
Marius Venter
Network Professional Services
African Technology Holdings
Block G, Hurlingham Office Park, co Republic and Woodlands Drive Hurlingham
Manor
) +27 (0) 11 787 9997 (Office Number)
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E-mail: marius@aict.co.za
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Michael
Sent: Monday, April 03, 2006 10:06 AM
To: 'sheng li'; catwater@aussiemail.com.au
Cc: ccielab@groupstudy.com
Subject: RE: OSPF - Hub & Spoke - Point-to-Multipoint
So this output would be expected in a partial mesh topology?
Thanks kindly.
R3#show ip ospf nei
Load for five secs: 0%/0%; one minute: 0%; five minutes: 0%
No time source, *17:41:35.786 MST Sun Feb 28 1993
Neighbor ID Pri State Dead Time Address Interface
66.162.1.2 1 FULL/DR 00:01:46 66.162.1.2 Serial1/0
N/A 0 ATTEMPT/DROTHER - 66.162.1.1 Serial1/0
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
sheng li
Sent: Monday, April 03, 2006 12:16 AM
To: Michael; catwater@aussiemail.com.au
Cc: ccielab@groupstudy.com
Subject: RE: OSPF - Hub & Spoke - Point-to-Multipoint
You need NBMA when lab instruction tells you NOT to
broadcast, or NOT to touch ospf network type, or to
elect DR (because P-M never has DR). I'd love to use
P-M whenever possible, however, P-M does introduce
some 32bit networks for those endpoints, maybe
something to worry about.
--- Michael <mamiller2@comcast.net> wrote:
> Ok, but doesn't Cisco documentation say differently?
> I'm really confused
> about this for some reason I don't understand yet.
> I do understand about
> TTL = 1. So with any configuration then R1 and R3
> will never be neighbors
> in OSPF? Only neighbors are spoke(s) & hub then?
>
> The optional OSPF interface settings only allow DR
> election & timer
> settings?
>
> So when would you logically use Cisco default NBMA
> OSPF interface rather
> than P-M?
>
>
> -----Original Message-----
> From: Charlie Atwater
> [mailto:catwater@AUSSIEMAIL.COM.AU]
> Sent: Sunday, April 02, 2006 11:15 PM
> To: mamiller2@comcast.net
> Cc: ccielab@groupstudy.com
> Subject: Re: OSPF - Hub & Spoke -
> Point-to-Multipoint
>
> Michael I believe this is because R1 and R2 are
> neighbors as are R2 and R3.
> But R1 and R3 are not actually neighbors.
>
> CAT
>
> --- mamiller2@comcast.net wrote:
>
> From: "Michael" <mamiller2@comcast.net>
> To: "ccielab" <ccielab@groupstudy.com>
> Subject: OSPF - Hub & Spoke - Point-to-Multipoint
> Date: Sun, 2 Apr 2006 21:43:09 -0600
>
> Hi All,
>
>
>
> I am trying to understand some information about FR
> Point-to-Multipoint
> network interfaces in a Hub and Spoke architecture.
> I think I just figured
> it out but I still would like to hear comments.
>
>
>
> R1 (Spoke) <-> R2 (Hub) <-> R3 (Spoke)
>
>
>
> All three routers are physically connected to a IOS
> router and configured
> using routed PVC's. Is it because of the routed
> pvc's that I do not see "IP
> OSPF Neighbors" of R3 in R1?
>
>
>
> I am using physical (multipoint) interfaces with
> frame maps.
>
>
>
> Is it true that switched pvc's in my IOS router
> would react differently?
>
>
>
> Thanks,
>
> Michael
>
>
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