From: dusth@comcast.net
Date: Fri Nov 11 2005 - 11:53:43 GMT-3
Hi Leigh,
Thanks for the explanation on the next-hop-self, I the lab a while back but still keep my configuration so that's why I'm asking this question since I forget the concept. In my config, this is the iBGP and I do have the next-hop-self since I do not have IGP run on one of my peer BGP to the out side peer, but I could figure out the next-hop-self is for the tunnel reachability as well. I'm always thinking that this next-hop-self is only for router do the IGP reach abillity since I do not have IGP routing from my internal BGP to external router.
Thanks,
Dustin
-------------- Original message --------------
> Hey chap,
>
> It depends on the layout of your lab and the rules you're playing by.
>
> If you've got bgp neighbours next to eachother in the same AS, then:
> router bgp 1234
> neigh 1.2.3.4 remote-as 1234
>
> If it's a different as:-
> router bgp 1234
> neigh .1.2.3.4 remote-as 4321
>
> If they are not next to eachother (different AS), then you'll need to add:-
> neigh 1.2.3.4 ebgp-multi-hop
>
> If you're not allowed to pass the routes through an igp and your router
> doesn't know how to get there, then add:-
> neigh 1.2.3.4 next-hop-self
>
> The train of though goes:-
> If you can see him to peer with him (remember bgp peering uses tcp),
> then you must be able to route to him.
>
> It took me one very long night and a lot of coffee to grasp this one.
> One of my routers in bgp did not have a route to the next hop and
> wouldn't do a thing with the routes. When I *eventually* put in
> next-hop-self (on the advertising router), it sent it to the router that
> gave him the routes.
>
> Have a crack at a combination of the above. If I'm miles away, then
> post some of the question and I'll see if I can't be more specific.
>
> LH
>
> dusth@comcast.net wrote:
>
> >Hi Leigh, Yes, you are right. I can make the tunnel up and BGP traverse inside
> the tunnel if I give tunnel ip address and using tunnel ip address for peering.
> However, usually additional ip address and floating static route are not allowed
> and if I can not redistribute BGP into IGP:) What would be the better solution?
> Dustin
> >
> >-------------- Original message --------------
> >
> >
> >
> >>Quick note - if you do put that route in, the tunnel will collapse...
> >>As it'll think the destination of the tunnel is down the tunnel...
> >>
> >>Give the tunnel an ip address and peer with that as a test.
> >>
> >>LH
> >>
> >>Godswill Oletu wrote:
> >>
> >>
> >>
> >>>Dustine,
> >>>
> >>>nei 4.4.4.4 update-source loopback0
> >>>
> >>>Tell this router that, when it is negotiating bgp session with neighbor
> >>>4.4.4.4, it should present the ip address on interface loopback0 as its
> >>>source address.
> >>>
> >>>If you debug bgp on this router or on the remote router, you will discover
> >>>that this router is actually using the ip address of loopback0 as its source
> >>>address.
> >>>
> >>>But for this router to reach neighbor 4.4.4.4, it will go to your IGP
> >>>routing table and pick the next hop address to reach 4.4.4.4 and will send
> >>>the traffic to neighbor 4.4.4.4 through the next hop address in your
> >>>routing table. If that next hop address is through the tunnel14, then the
> >>>traffic will go through the tunnel14 interface.
> >>>
> >>>So, the answer to your question will a No.
> >>>
> >>>But if you do "ip route 4.4.4.4 255.255.255.255 tunnel 14'
> >>>
> >>>Then, bgp traffic will attempt to reach neighbor 4.4.4.4 via tunnel 14.
> >>>
> >>>HTH
> >>>Godswill Oletu
> >>>
> >>>
> >>>----- Original Message -----
> >>>From:
> >>>To:
> >>>Sent: Thursday, November 10, 2005 7:05 PM
> >>>Subject: BGP and Tunnel
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>>Hi all, I need some clarification on how does bgp know to traverse inside
> >>>>
> >>>>
> >>>>
> >>>>
> >>>the tunnel and what parameter of the tunnel interface tell that for bgp end
> >>>points? I do not have access to the lab right now so I can not verify the
> >>>config.
> >>>
> >>>
> >>>
> >>>
> >>>>Here is the example:
> >>>>r1:
> >>>>interface tunnel 14
> >>>>ip unnumber loopback 0
> >>>>tunnel source 1.1.1.1
> >>>>tunnel destination 4.4.4.4
> >>>>bgp 10
> >>>>nei 4.4.4.4 remote-as 10
> >>>>nei 4.4.4.4 update-source loopback0
> >>>>Does the ip unnumber of the tunnel or the tunnel source & destination tell
> >>>>
> >>>>
> >>>>
> >>>>
> >>>router that bgp traffic need to traverse inside the tunnel?
> >>>
> >>>
> >>>
> >>>
> >>>>Thanks in advance,
> >>>>Dustin
> >>>>
> >>>>_______________________________________________________________________
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> >>>>
> >>>>
> >>>>
> >>>>
> >>>_______________________________________________________________________
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> >>>
> >>>
> >>_______________________________________________________________________
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> >>
> >>
> >
> >_______________________________________________________________________
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