From: Scott Meeuwsen (scott@xxxxxxxxxxxx)
Date: Mon Dec 31 2001 - 15:22:17 GMT-3
Stephen,
The rule of syncronization isn't about next hops, next hop must always be
reachable (Not necessarily via an IGP though and possibly via recursive BGP
routes), synchronization on or off. Synchronization is about whether the
destination prefix is reachable already via an IGP, in your case OSPF. In
other words, if the the BGP information isn't redundant (the router already
knows how to get there) you must turn off synchronization.
Not 100% sure why this isn't working in your case since to me 5.0.0.0/8
satifies this criteria, but it is listed as unsynchronized so for whatever
reason it is NOT satisfying the synchronization rule. My best guess (total
guess) is that the reason is because info is known via an E2 route which
means the route is learned outside the autonomous system and may have come
from BGP originally. Thus the route is not trustable in BGP's eyes... Try
making the route an O, O IA, or S (quick plop in a static route to null0)
and see if it it synchronizes...
--Scott
----- Original Message -----
From: "Stephen Oliver" <stevie_oliver@hotmail.com>
To: <Parry.Chua@compaq.com>; <fred190044@hotmail.com>;
<ccielab@groupstudy.com>
Sent: Monday, December 31, 2001 8:53 AM
Subject: RE: BGP routes.
> Parry,
>
> Here's the BGP table and routing table along with the output from one of
the
> prefixes not being marked as best.
>
> As you see the route has a next hop of 137.6.2.17 from router with RID of
> 137.6.2.2. Both these prefixes are in the main routing table so my
> understanding was that the route should be marked best. I know I can turn
> off synchronization and get it to work but I didn't think I had to if the
> next hop was reachable. If I have to do a no sync then fine and my
> understanding of the rule is at fault.
>
> Thanks, Stephen.
>
> Network Next Hop Metric LocPrf Weight Path
> * i0.0.0.0 137.6.2.9 100 0 i
> * i5.0.0.0 137.6.2.17 0 100 0 111 100 i
> * i6.0.0.0 137.6.2.17 0 100 234 100 i
> * i7.0.0.0 137.6.2.17 0 100 0 100 i
> * i137.6.1.1/32 137.6.2.17 0 100 0 100 i
> * i137.6.2.2/32 137.6.2.9 0 100 0 i
> * i137.6.2.8/29 137.6.2.10 0 100 0 i
> *> 0.0.0.0 0 32768 i
> * i137.6.2.16/30 137.6.2.9 0 100 0 i
> *> 137.6.3.3/32 0.0.0.0 0 32768 i
> * 137.6.3.16/28 137.6.3.18 0 0 300 i
> *> 0.0.0.0 0 32768 i
> 2612#show ip bgp 5.0.0.0
> BGP routing table entry for 5.0.0.0/8, version 0
> Paths: (1 available, no best path)
> Not advertised to any peer
> 111 100
> 137.6.2.17 (metric 176) from 137.6.2.10 (137.6.2.2)
> Origin IGP, metric 0, localpref 100, valid, internal, not
synchronized
> Originator: 137.6.2.2, Cluster list: 137.6.5.5
> 2612#show ip route
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter
> area
> * - candidate default, U - per-user static route, o - ODR
> P - periodic downloaded static route
>
> Gateway of last resort is not set
>
> 137.6.0.0/16 is variably subnetted, 9 subnets, 4 masks
> O 137.6.2.9/32 [110/128] via 137.6.2.10, 00:04:25, Serial0/0
> C 137.6.2.8/29 is directly connected, Serial0/0
> O 137.6.2.10/32 [110/64] via 137.6.2.10, 00:04:25, Serial0/0
> O IA 137.6.2.2/32 [110/129] via 137.6.2.10, 00:02:30, Serial0/0
> O IA 137.6.5.5/32 [110/65] via 137.6.2.10, 00:02:30, Serial0/0
> O E2 137.6.1.1/32 [110/78] via 137.6.2.10, 00:02:30, Serial0/0
> C 137.6.3.3/32 is directly connected, Loopback0
> C 137.6.3.16/28 is directly connected, Ethernet0/0
> O 137.6.2.16/30 [110/176] via 137.6.2.10, 00:04:26, Serial0/0
> O E2 5.0.0.0/8 [110/78] via 137.6.2.10, 00:02:31, Serial0/0
> O E2 6.0.0.0/8 [110/78] via 137.6.2.10, 00:02:31, Serial0/0
> O E2 7.0.0.0/8 [110/78] via 137.6.2.10, 00:02:31, Serial0/0
> 2612#
>
>
> >From: "Chua, Parry" <Parry.Chua@compaq.com>
> >To: "Stephen Oliver" <stevie_oliver@hotmail.com>,
<fred190044@hotmail.com>,
> ><ccielab@groupstudy.com>
> >Subject: RE: BGP routes.
> >Date: Mon, 31 Dec 2001 08:59:53 +0800
> >
> >Hi,
> >
> >Do a show ip bgp a.b.c.d and see nwhat is the reason that it is NOT the
> >best route,
> >if it is "no sync" and the route of a.b.c.d is from ospf, then you
> >should check the RID
> >of the network a.b.c.d
> >
> > > Parry Chua
> > >
> >
> >
> >-----Original Message-----
> >From: Stephen Oliver [mailto:stevie_oliver@hotmail.com]
> >Sent: Saturday, December 29, 2001 7:02 PM
> >To: fred190044@hotmail.com; ccielab@groupstudy.com
> >Subject: Re: BGP routes.
> >
> >
> >Fred,
> >
> >Well, for example, the 5.0.0.0 route is in the bgp table with next hop
> >as
> >137.6.2.17. This route is in the routing table, 137.6.2.16/30 but the 5
> >
> >prefix is not marked as best in the bgp table. I am trying to do this
> >by
> >not setting no sync just to test the bgp rules. I thought that since
> >the
> >next hop is reachable through an IGP then it would be marked as *> in
> >the
> >bgp table. I can get the route to be marked as *> by setting no sync
> >but I
> >wanted to avoid using this if I could. I probably just misunderstand
> >the
> >synchronization rule.
> >
> >Thanks, Stephen.
> >
> >
> > >From: "Fred Danson" <fred190044@hotmail.com>
> > >To: ccielab@groupstudy.com
> > >CC: stevie_oliver@hotmail.com
> > >Subject: Re: BGP routes.
> > >Date: Fri, 28 Dec 2001 09:42:48 -0500
> > >
> > >Which prefix is not working properly? Do you have "no sync" set in this
> >
> > >router? Would you mind posting your configs?
> > >
> > >
> > >>From: "Stephen Oliver" <stevie_oliver@hotmail.com>
> > >>Reply-To: "Stephen Oliver" <stevie_oliver@hotmail.com>
> > >>To: ccielab@groupstudy.com
> > >>Subject: BGP routes.
> > >>Date: Fri, 28 Dec 2001 12:09:54 +0000
> > >>
> > >>I have a BGP network with OSPF running along side. A loopback
> >propogates
> > >>through the BGP tables but on one router it is not installed as best
> >even
> > >>though OSPF provides a route to the next hop in the routing table. I
> > >>thought if this criteria was met the BGP table would mark the route as
> > >
> > >>for
> > >>best. The routing and BGP tables are below.
> > >>
> > >>Any ideas ?
> > >>
> > >>Thanks, Stephen.
> > >>
> > >>Gateway of last resort is not set
> > >>
> > >> 137.6.0.0/16 is variably subnetted, 9 subnets, 4 masks
> > >>O 137.6.2.9/32 [110/128] via 137.6.2.10, 00:00:12, Serial0/0
> > >>C 137.6.2.8/29 is directly connected, Serial0/0
> > >>O 137.6.2.10/32 [110/64] via 137.6.2.10, 00:41:05, Serial0/0
> > >>O IA 137.6.2.2/32 [110/129] via 137.6.2.10, 00:08:44, Serial0/0
> > >>O E2 137.6.1.1/32 [110/78] via 137.6.2.10, 00:08:44, Serial0/0
> > >>O IA 137.6.5.5/32 [110/65] via 137.6.2.10, 00:08:44, Serial0/0
> > >>C 137.6.3.3/32 is directly connected, Loopback0
> > >>C 137.6.3.16/28 is directly connected, Ethernet0/0
> > >>O 137.6.2.16/30 [110/176] via 137.6.2.10, 00:41:06, Serial0/0
> > >>O E2 5.0.0.0/8 [110/78] via 137.6.2.10, 00:08:46, Serial0/0
> > >>O E2 6.0.0.0/8 [110/78] via 137.6.2.10, 00:08:46, Serial0/0
> > >>O E2 7.0.0.0/8 [110/78] via 137.6.2.10, 00:08:46, Serial0/0
> > >>2612#show ip bgp
> > >>BGP table version is 4, local router ID is 137.6.3.3
> > >>Status codes: s suppressed, d damped, h history, * valid, > best, i -
> > >>internal
> > >>Origin codes: i - IGP, e - EGP, ? - incomplete
> > >>
> > >> Network Next Hop Metric LocPrf Weight Path
> > >>* i5.0.0.0 137.6.2.17 0 100 0 111 100 i
> > >>* i6.0.0.0 137.6.2.17 0 100 0 100 i
> > >>* i7.0.0.0 137.6.2.17 0 100 0 100 i
> > >>* i137.6.1.1/32 137.6.2.17 0 100 0 100 i
> > >>* i137.6.2.2/32 137.6.2.9 0 100 0 i
> > >>* i137.6.2.8/29 137.6.2.10 0 100 0 i
> > >>*> 0.0.0.0 0 32768 i
> > >>* i137.6.2.16/30 137.6.2.9 0 100 0 i
> > >>*> 137.6.3.3/32 0.0.0.0 0 32768 i
> > >>* 137.6.3.16/28 137.6.3.18 0 0 300 i
> > >>*> 0.0.0.0 0 32768 i
> > >>
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