From: cebuano (cebu2ccie@cox.net)
Date: Sun Oct 13 2002 - 02:16:51 GMT-3
Dave,
You might want to check this...
http://www.cisco.com/warp/public/104/24.html
HTH,
Elmer
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Dave Cooper
Sent: Saturday, October 12, 2002 10:43 PM
To: CCIE
Subject: RE: OSPF NBMA - Hub and Spokes
Hi
Thanks for all the replies.
I tried 2 options suggested
1. p-2-mp : this works fine
2. NBMA : On all interfaces (r1,r2&r3). Each has
neighbor config for other 2 routers. I've set ospf
priority as
r1 = 100
r2 = 50
r3 = 60
Adj. is not formed between R2 and R3. I get TTL exceed
drop messages as R1 (Src=R2 Dest=R3 & vice versa)
Also R1 is rightfully elected as DR. But both R2 and
R3 think that they are BDR.
I guess for NBMA network to work properly (each router
is neighbor of every other router) on frame relay, we
need to have full mesh. Otherwise DR/BDR election
process is screwed.
Comments ??
Thanks
Deepesh
>
> Hi
>
>
> r1-----r2
> |
> |-----r3
>
>
> - Version 12.1(11.6). All interfaces are frame relay
> sub interfaces.
> - OSPF Area=1 for all interfaces
> - r1 interface is p-2-m. Has frame-r map to r2 & r3
> (have added broadcast too in the map command)
> - r2 is p-2-p. Has frame-r interface-dlci going to
> r1
> (On 12.1 frame-r map is not allowed on p-2-p)
> - r3 is p-2-p. Has frame-r interface-dlci going to
> r1
> (frame-r map is not allowed)
> - I can ping from every router to every other
> router.
>
> Problem 1
> =========
> On r1 - sh ip ospf inter shows interface as NBMA.
> Also
> I've added nei as r1 and r3. OSPF pri = 100
> On r2 - sh ip ospf inter shows interface as p-2-p.I
> didn't add neibhor.
> On r3 - sh ip ospf inter shows interface as p-2-p.I
> didn't add neibhor.
>
> I can't form adjacency between r1--r2 & r1--r3.
> However if I make r2 & r3 interface as NBMA and add
> r1
> as neighbor (on both r2 & r3), adj. is formed.
>
> I think, few days back I saw email (if hub is nbma,
> spoke need not be NBMA) which was contrary to what
> I'm
> seeing.
>
> Should we have hub=NBMA && spoke(s)=NBMA ??
>
>
> Problem 2
> =========
> further,
> On r2 - I add r3 as neighbor
> On r3 - I add r2 as neighbor
> Adj is not formed, even though r2 & r3 can ping each
> other. I keep getting TTL exceed drop messages on R1
> (source=r2, dest=r3 and vice versa)
>
> Why are pings going through but adj is not formed ??
>
> Am I missing something really basic here ?
>
>
> thanks
> Dave
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