From: Venkataramanaiah.R (vramanaiah@gmail.com)
Date: Thu Nov 24 2005 - 11:03:09 GMT-3
Ah, now i got the problem that you running into.. i am sorry, i did
assilimate your first e-mail well..
As you mentioned, it should work if you used a seperate net for the
tunnel i/f, if you use ip unnumbered, then BGP, will use the loopbacks
as next hop and then in the forwarding plane, the tunnel i/f will not
be used and would be normally routed via R2 resulting in blackhole. If
you use a different subnet, it would then send the traffic via the
tunnel which would be GRE encapsulation. R2 will transparently
forward it to the other router...
-Venkat
On 11/24/05, Venkataramanaiah.R <vramanaiah@gmail.com> wrote:
> Agree, Tunnel sounds like a good idea to avoid redistribution of BGP
> table. Never thought about this before..
>
> However, i do not understand the issue that you have with the tunnel
> i/f.. R u saying the tunnel keeps flapping? Then make tunnel interface
> as passive. it would then never run eigrp on it and the chicken/Egg
> story will be stopped..
>
> -Venkat
>
> On 11/24/05, Anthony Sequeira <terry.francona@gmail.com> wrote:
> > Hi Leigh!
> >
> > Errr - take another look - R1 and R4 are running iBGP with each other -
> > setting NEXT-HOP-SELF on the peering from R1 to R4 will have no effect.
> > Since R4 must use R2 to reach R1 - traffic will still be black-holed at R2.
> >
> >
> >
> > On 11/24/05, Leigh Harrison <ccileigh@gmail.com> wrote:
> > > Hey there Anthony,
> > >
> > > If you don't want to redistribute bgp into igp (not that popluar with
> > > me!), then you could pop in "next-hop-self".
> > >
> > > This way the next hop for the destinations can be found via the igp. No
> > > redistributing required. :)
> > >
> > > LH
> > >
> > > Anthony Sequeira wrote:
> > >
> > > >Hi *Venkataramanaiah.R!*
> > > >You are correct in that we do not need a tunnel for the iBGP peering to
> > work
> > > >between R1 and R4 through R2. As you know - the iBGP peerings do not need
> > to
> > > >be direct connections. The issue will come later with reachability. For
> > > >example - if we advertise a prefix into BGP on R1 - R4 will not have
> > > >reachability due to a "black-hole" situation on R2.
> > > >
> > > >I do not want to redistribute BGP into the IGP here - so I wanted to play
> > > >with the tunnel option as I describe here.
> > > >
> > > >
> > > >
> > > >On 11/24/05, Venkataramanaiah.R <vramanaiah@gmail.com> wrote:
> > > >
> > > >
> > > >>I do not understand the need for tunnel interfaces here for the IBGP
> > > >>to work via R2. Am i missing something here?
> > > >>
> > > >>-Venkat
> > > >>
> > > >>On 11/24/05, Tim <ccie2be@nyc.rr.com> wrote:
> > > >>
> > > >>
> > > >>>A couple things I noticed:
> > > >>>
> > > >>>1) The tunnel endpoints should be on R1 and R4, not R2.
> > > >>>
> > > >>>2) You didn't adjust the cost of the tunnel to make it less preferred
> > > >>>
> > > >>>
> > > >>path
> > > >>
> > > >>
> > > >>>than the physical path.
> > > >>>
> > > >>>3) I would use the physical interface as the tunnel source on each
> > > >>>
> > > >>>
> > > >>router.
> > > >>
> > > >>
> > > >>>4) If using the lo0 for the tunnel ip address doesn't work, you can
> > try
> > > >>>using the ip address of the physical interface for the tunnel address.
> > > >>>
> > > >>>Just a couple ideas,
> > > >>>
> > > >>>Tim
> > > >>>
> > > >>>-----Original Message-----
> > > >>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > > >>>Anthony Sequeira
> > > >>>Sent: Wednesday, November 23, 2005 9:42 PM
> > > >>>To: Cisco certification
> > > >>>Subject: Let's Tunnel BGP Due to Non-BGP Speaker in Transit Path!
> > > >>>
> > > >>>I want to tunnel my iBGP peering from R1 to R4 because R2 is not
> > running
> > > >>>BGP. I want to use the loopback 0 interfaces for the peerings. The IGP
> > > >>>
> > > >>>
> > > >>in
> > > >>
> > > >>
> > > >>>use is EIGRP and all of the interfaces shown below are running EIGRP.
> > > >>>
> > > >>>
> > > >>>
> > > >>>R1-----4.4.8.0 /24-----R2-----4.4.12.0/24-----R4
> > > >>>
> > > >>>
> > > >>>
> > > >>>R1 lo0 4.4.1.1/24
> > > >>>
> > > >>>R4 lo0 4.4.4.4/24
> > > >>>
> > > >>>
> > > >>>
> > > >>>I have this sample scenario labbed up and I am having a heck of a time.
> > > >>>
> > > >>>
> > > >>I
> > > >>
> > > >>
> > > >>>have tried the following with no luck:
> > > >>>
> > > >>>
> > > >>>
> > > >>>Attempt 1
> > > >>>
> > > >>>R1:
> > > >>>
> > > >>>int tunnel 0
> > > >>>
> > > >>>ip unnumbered lo0
> > > >>>
> > > >>>tunnel source 4.4.8.1
> > > >>>
> > > >>>tunnel destination 4.4.12.4
> > > >>>
> > > >>>
> > > >>>
> > > >>>R2:
> > > >>>
> > > >>>int tunnel 0
> > > >>>
> > > >>>ip unnumbered lo0
> > > >>>
> > > >>>tunnel source 4.4.12.4
> > > >>>
> > > >>>tunnel destination 4.4.8.1
> > > >>>
> > > >>>
> > > >>>
> > > >>>Attempt 2
> > > >>>
> > > >>>R1:
> > > >>>
> > > >>>int tunnel 0
> > > >>>
> > > >>>ip unnumbered lo0
> > > >>>
> > > >>>tunnel source lo0
> > > >>>
> > > >>>tunnel destination 4.4.4.4
> > > >>>
> > > >>>
> > > >>>
> > > >>>R2:
> > > >>>
> > > >>>int tunnel 0
> > > >>>
> > > >>>ip unnumbered lo0
> > > >>>
> > > >>>tunnel source lo0
> > > >>>
> > > >>>tunnel destination 4.4.1.1
> > > >>>
> > > >>>
> > > >>>
> > > >>>You see this is easy and works great if I create a new subnet for the
> > > >>>tunnel and use that in my BGP peerings the issue that I am having is
> > > >>>trying to use the loopback addresses for the peerings and still use my
> > > >>>tunnel.
> > > >>>
> > > >>>
> > > >>>
> > > >>>I notice that my tunnel interface does not show up in the routing table
> > > >>>
> > > >>>
> > > >>when
> > > >>
> > > >>
> > > >>>I am pulling the address from the loopback..I guess this must be why
> > my
> > > >>>
> > > >>>
> > > >>BGP
> > > >>
> > > >>
> > > >>>is not using it????
> > > >>>
> > > >>>
> > > >>>
> > > >>>Anyone feel like labbing this one up and trying this one? Or is it
> > > >>>
> > > >>>
> > > >>something
> > > >>
> > > >>
> > > >>>really simple that I am missing about tunnels?
> > > >>>
> > > >>>
> > > >>>
> > > >>>Thanks in advance for you consideration of this e-mail.
> > > >>>
> > >
> > >>>_______________________________________________________________________
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> > >
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> > > >>>
> > > >>>
> > > >
> > >
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