From: Manish Gupta (manishgu@cisco.com)
Date: Wed Nov 13 2002 - 06:14:59 GMT-3
Hi Wang
May be I am wrong. But the way I think, here is how OSPF works.
Everytime when we enable OSPF on a router. That router sends a HELLO
packet to "DIRECTLY" connected segments only. As in your case For Router C
& A, Router B is the only directly connected router with them. Thats why
the HELLO packets exchange will be only between A<--->B & B<---C but NOT in between
A<--->C as they are not connected directly.
If you ping A to C or vice-versa it works becuase under lying layer-2
(Frame Relay) already have map ip statement. But as far we talks about
OSPF HELLO packets. It just between directly connected only.
Thanks
-Manish
On Wed, 13 Nov 2002, Wang Tao wrote:
> Hi, Manish,
>
> The topology is just as what you drew below.
> As you said, in NBMA mode only directly connected neighbor can form
> neighborship.
>
> But why it need directly connect to build neighbor?
> I think Jl yan is right. In NBMA or Broadcast, the ttl of hello packet is
> set to 1.So you will find
> ping is successful but not be able to build neighbor with each other.
>
> Thanks & Regads
>
> Tao
>
> ----- Original Message -----
> From: "Manish Gupta" <manishgu@cisco.com>
> To: "jl yan" <yanjunling@hotmail.com>
> Cc: <wangtao_sh@hotmail.com>; <spage@nc.rr.com>; <ccielab@groupstudy.com>
> Sent: Wednesday, November 13, 2002 3:54 PM
> Subject: RE: OSPF on NBMA
>
>
> > Hi Tao
> >
> > I think your topology is like:
> >
> > <B>
> > | |
> > | |
> > | |
> > <C> <A>
> >
> > In this case, If B is DR, everything should work fine. But if you want to
> > make either A or C DR, In that case they will only form neighbor ship with
> > B only cause media is NBMA. In NBMA mode only directly connected neighbor
> > can form neighborship.
> >
> >
> > -Manish
> >
> >
> >
> >
> > On Wed, 13 Nov 2002, jl yan wrote:
> >
> > > I think the ttl vaule equals to 1. so it can ping each other but cannot
> > > establish neighbor
> > >
> > >
> > >
> > >
> > >
> > >
> > > >From: "Tao Wang" <wangtao_sh@hotmail.com>
> > > >Reply-To: "Tao Wang" <wangtao_sh@hotmail.com>
> > > >To: spage@nc.rr.com, ccielab@groupstudy.com
> > > >Subject: RE: OSPF on NBMA
> > > >Date: Wed, 13 Nov 2002 13:11:47 +0800
> > > >
> > > >I see this config should work.
> > > >But my question is that in NBMA if I could ping successully whether I
> could
> > > >build neigbor with the command "neighbor" even these two nodes haven't
> > > >directly PVC.
> > > >
> > > >
> > > >>From: "Jake Jake" <spage@nc.rr.com>
> > > >>To: "Tao Wang" <wangtao_sh@hotmail.com>, <ccielab@groupstudy.com>
> > > >>Subject: RE: OSPF on NBMA
> > > >>Date: Wed, 13 Nov 2002 00:10:17 -0500
> > > >>
> > > >>Configure B as the DR. Use neighbor statements on B pointing to A and
> to
> > > >C.
> > > >>Make sure A and C had low ospf priority so they dont become DR upon
> > > >reboot.
> > > >>
> > > >>
> > > >>-----Original Message-----
> > > >>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Tao
> > > >>Wang
> > > >>Sent: Tuesday, November 12, 2002 11:01 PM
> > > >>To: ccielab@groupstudy.com
> > > >>Subject: Q: OSPF on NBMA
> > > >>
> > > >>
> > > >>Dear all,
> > > >>
> > > >>I have question on OSPF on FR NBMA.
> > > >>
> > > >>There are 3 nodes--- A B and C. They build a Hub-Spoke structure. B is
> > > >HUB.
> > > >>
> > > >>Now I config to make C as DR and using the command "neighbor" to let B
> and
> > > >>A as the neighbors of C.
> > > >>On A B and C, I have made static maps to make them be able to ping
> each
> > > >>others successfully.
> > > >>
> > > >>But the result is C and A couldn't build neighbor with each other.
> > > >>I don't understand the command "neighbor" very much.C should use the
> > > >>unicast to send the hello
> > > >>packet to A. If C should ping A successfully, then the hello packet
> from C
> > > >>should be able to get A.
> > > >>
> > > >>From the result, I think if two nodes want to build neighbors with
> each
> > > >>other in NBMA, they should
> > > >>have dirctly PVC between them.But I don't know why exactly.
> > > >>
> > > >>Does someone please help?
> > > >>
> > > >>Thanks & Regards
> > > >>
> > > >>Tao
> > > >>
> > > >>
> > > >>
> > > >>
> > > >>
> > > >>_________________________________________________________________
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> > > >
> > > >
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