From: Brian Dennis (brian@xxxxxx)
Date: Sat May 05 2001 - 12:33:44 GMT-3
If you're talking about the next-hop-address for a BGP route you're right,
you can't use a default route for it. You can use any valid route that
matches but the default route when looking up the next-hop-address.
Okay that being said, how do you get around this issue of BGP not using the
default for the next-hop-address? Think creatively. What would be the next
best thing to a default?
Brian Dennis, CCIE #2210 (R&S)(ISP/Dial) CCSI #98640
5G Networks, Inc.
brian@5g.net
(925) 260-2724
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Chuck Larrieu
> Sent: Saturday, May 05, 2001 7:57 AM
> To: Norma Schutt; mcaplan.cs@clearstream.com; ccielab@groupstudy.com
> Subject: RE: Default route not good enough for EBGP session
>
>
> Hhhmmmm.... You know, that might just explain a phenomenon I have been
> seeing.
>
> I've done this a couple of times now - hooked up with people and run BGP
> across the internet. ( yes it can be done and yes it offers a lot of
> opportunity to try things that would be difficult to duplicate in a modest
> home lab. )
>
> Essentially, my compatriot and I will set up BGP between our public side
> interfaces. With both iBGP and eBGP, one must use the
> ebgp-multihop command
>
> On my routers I have my usual default 0.0.0.0 0.0.0.0 ip of my isp router
>
> Things do not come up, and my partner and I fumble around until we try a
> defined static - his ip address to next hop my isp router
>
> Doh!
>
> To put this into the study / mastery perspective, it does make sense. BGP
> looks for a specific route, not just any old route. It's been a
> while since
> I looked at the RFC, but my recollection is that the RFC assumes directly
> connected networks. Multihop and use of loopbacks must be the result of
> revisions based on real world experience after the RFC was published.
>
> Chuck
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Norma Schutt
> Sent: Friday, May 04, 2001 10:49 PM
> To: mcaplan.cs@clearstream.com; ccielab@groupstudy.com
> Subject: Re: Default route not good enough for EBGP session
>
> I read somewhere but can't remember where it was now that you can't use a
> default route to set up your EBGP sessions. If you aren't using the
> directly connected interfaces, then you must have a specific route to the
> EBGP neighbor's loopback.
>
> 3 days and 7 hours.......
> Norma Schutt
>
>
> At 10:55 AM 5/4/2001, mcaplan.cs@clearstream.com wrote:
> >HI,
> >
> >I have a very simple set up
> >
> >(lo 0)R1----frame PVC-----R2(lo 0)
> >
> >Configs ar shown below. I am setting up EBGP between R1 and R2,
> using Lo 0
> >as the peer IP address in both cases. I can do an extended ping
> from R1 to
> >R2 usng Lo 0 as the source address. The neighbor relationship
> however will
> >not progress beyond active.
> >The following is the output from debug ip bgp
> >
> >03:59:52: BGP: 11.11.11.11 multihop open delayed 19344ms (no route)
> >
> >There is a route, but it just happens to be the default route.
> It all works
> >fine if I put a more precise route onto R1 or R2. Why does it fail with
> >default routes, when extended ping works fine ?
> >
> >
> >R1
> >
> >interface Loopback0
> > ip address 10.10.10.10 255.255.255.255
> > no ip directed-broadcast
> >!
> >interface Serial0
> > ip address 12.1.1.1 255.0.0.0
> > no ip directed-broadcast
> > encapsulation frame-relay
> >!
> >router bgp 1
> > neighbor 11.11.11.11 remote-as 2
> > neighbor 11.11.11.11 ebgp-multihop 255
> > neighbor 11.11.11.11 update-source Loopback0
> >!
> >ip classless
> >ip route 0.0.0.0 0.0.0.0 12.2.2.2
> >
> >Gateway of last resort is 12.2.2.2 to network 0.0.0.0
> >
> > 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
> >C 10.10.10.10/32 is directly connected, Loopback0
> >C 10.1.0.0/16 is directly connected, TokenRing0
> >C 12.0.0.0/8 is directly connected, Serial0
> >S* 0.0.0.0/0 [1/0] via 12.2.2.2
> >
> >R2
> >
> >interface Loopback0
> > ip address 11.11.11.11 255.255.255.255
> > no ip directed-broadcast
> >!
> >interface Serial0
> > ip address 12.2.2.2 255.0.0.0
> > no ip directed-broadcast
> > encapsulation frame-relay
> > no ip route-cache
> > no ip mroute-cache
> > logging event subif-link-status
> > logging event dlci-status-change
> > no fair-queue
> > clockrate 2000000
> >!
> >router bgp 2
> > neighbor 10.10.10.10 remote-as 1
> > neighbor 10.10.10.10 ebgp-multihop 255
> > neighbor 10.10.10.10 update-source Loopback0
> >!
> >ip classless
> >ip route 0.0.0.0 0.0.0.0 12.1.1.1
> >
> >Gateway of last resort is 12.1.1.1 to network 0.0.0.0
> >
> > 11.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
> >C 11.11.11.11/32 is directly connected, Loopback0
> >C 11.1.0.0/16 is directly connected, Ethernet0
> >C 12.0.0.0/8 is directly connected, Serial0
> >S* 0.0.0.0/0 [1/0] via 12.1.1.1
> >
> >
> >Any advice with this strange behaviour ?
> >
> >Cheers
> >
> >Mark
> >
> >
> >Visit us at http://www.clearstream.com
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