From: mcaplan.cs@xxxxxxxxxxxxxxx
Date: Sat May 05 2001 - 16:45:13 GMT-3
Thanks to everyone for their comments on this one.
Its just a quirk worth remembering......dont rely on a default route for
eBGP neighbors.
Cheers
Mark
> ----------
> From: Brian Dennis[SMTP:brian@5g.net]
> Sent: Samstag, 5. Mai 2001 17:33
> To: Chuck Larrieu; Norma Schutt; mcaplan.cs@clearstream.com;
> ccielab@groupstudy.com
> Subject: RE: Default route not good enough for EBGP session
>
> 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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