From: Vazquez, Jorge (Jorge.Vazquez@acs-inc.com)
Date: Fri Mar 07 2008 - 15:41:40 ARST
I am using version 12.2(44), your link is mentioning something about the IOS
version may make the router stop advertising those routes.
Jorge
_____
From: Carlos Alberto Trujillo Jimenez
[mailto:carlos.trujillo.jimenez@gmail.com]
Sent: Friday, March 07, 2008 11:07 AM
To: Vazquez, Jorge
Cc: ccie forum
Subject: Re: BGP Table on the Lab Exam
Well, I labbed it, and in my lab topology it works fine.
The router is advertising the bgp prefix to its ebgp peer.
look, at the results from the router who has the "rib-faiulre" for the
prefix 7.7.7.0 <http://7.7.7.0> in the bgp table
r2#show ip bgp
BGP table version is 1310, local router ID is 172.16.102.1
<http://172.16.102.1>
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 <http://0.0.0.0> 172.16.10.4 <http://172.16.10.4>
0 100 0 (65000) 700 i
r> 7.7.7.0/24 <http://7.7.7.0/24> 172.16.10.4 <http://172.16.10.4>
0 100 0 (65000) 700 i
r2#show ip bgp rib-failure
Network Next Hop RIB-failure RIB-NH
Matches
7.7.7.0/24 <http://7.7.7.0/24> 172.16.10.4 <http://172.16.10.4>
Higher admin distance Yes
r2#show ip bgp 7.7.7.0 <http://7.7.7.0>
BGP routing table entry for 7.7.7.0/24 <http://7.7.7.0/24> , version 1316
Paths: (1 available, best #1, table Default-IP-Routing-Table,
RIB-failure(17))
Advertised to update-groups:
1 3
(65000) 700
172.16.10.4 <http://172.16.10.4> from 172.16.10.4 <http://172.16.10.4>
(172.16.104.1 <http://172.16.104.1> )
Origin IGP, metric 0, localpref 100, valid, confed-external, best
Router 2 is EBGP-PEERING with R5 and is also ADVERTISING prefix 7.7.7.0/24
<http://7.7.7.0/24>
r2#show ip bgp neighbors 172.16.25.5 <http://172.16.25.5> advertised-routes
BGP table version is 1317, local router ID is 172.16.102.1
<http://172.16.102.1>
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 <http://0.0.0.0> 172.16.10.4 <http://172.16.10.4>
0 100 0 (65000) 700 i
r> 7.7.7.0/24 <http://7.7.7.0/24> 172.16.10.4 <http://172.16.10.4>
0 100 0 (65000) 700 i
Total number of prefixes 2
r2#
In router 5, I can see the prefix 7.7.7.0 <http://7.7.7.0> is present in
the bgp table.
r5#show ip bgp
BGP table version is 3, local router ID is 172.16.105.1
<http://172.16.105.1>
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 <http://0.0.0.0> 172.16.25.2 <http://172.16.25.2>
0 100 700 i
*> 7.7.7.0/24 <http://7.7.7.0/24> 172.16.25.2 <http://172.16.25.2>
0 100 700 i
I found other sources that talk about the propagation of "rib-failure"
prefixes under bgp.
and as in my lab it is working. let me see if can see another example of
when a rib-failure network is not propagated.
http://ioshints.blogspot.com/2007/12/what-is-bgp-rib-failure.html
<http://ioshints.blogspot.com/2007/12/what-is-bgp-rib-failure.html>
Another question. did you lab it and get the results?
<http://www.cisco.com/en/US/docs/ios/12_2s/feature/guide/fs_sbair.html>
2008/3/7, Vazquez, Jorge <Jorge.Vazquez@acs-inc.com
<mailto:Jorge.Vazquez@acs-inc.com> >:
Please check this link, it says the routes are not advertised.
http://www.cisco.com/warp/public/459/bgpfaq_5816.shtml#twenty-three
<http://www.cisco.com/warp/public/459/bgpfaq_5816.shtml#twenty-three>
Jorge
_____
From: Carlos Alberto Trujillo Jimenez
[mailto:carlos.trujillo.jimenez@gmail.com
<mailto:carlos.trujillo.jimenez@gmail.com> ]
Sent: Friday, March 07, 2008 10:18 AM
To: Vazquez, Jorge
Cc: ccie forum
Subject: Re: BGP Table on the Lab Exam
Jorge, it is not correct.
If you have routes in the BGP table under RIB-failure, those router are
ADVERTISED to is peer routers via bgp.
In my example router 2 and router 5 are peering via bgp.
Router 2 has the "RIB-FAILURE" for the prefix 7.7.7.0/24 <http://7.7.7.0/24>
because the same prefix via learned via ospf.
r2#show ip bgp
BGP table version is 1309, local router ID is 172.16.102.1
<http://172.16.102.1/>
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 <http://0.0.0.0/> 172.16.10.4 <http://172.16.10.4/>
0 100 0 (65000) 700 i
r> 7.7.7.0/24 <http://7.7.7.0/24> 172.16.10.4 <http://172.16.10.4/>
0 100 0 (65000) 700 i
r2#show ip route ospf
O E2 7.7.7.0 <http://7.7.7.0/> [110/1] via 172.16.10.4
<http://172.16.10.4/> , 03:54:12, Serial0/0/0
Now you form an EBGP-PEERING between router and and router 5 and check the
bgp table of router 5 to see if it is learning via bgp the prefix 7.7.7.0
<http://7.7.7.0/> .
r5#show ip bgp
BGP table version is 3, local router ID is 172.16.105.1
<http://172.16.105.1/>
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 7.7.7.0/24 <http://7.7.7.0/24> 172.16.25.2 <http://172.16.25.2/>
0 100 700 i
The prefix is present.
2008/3/7, Vazquez, Jorge <Jorge.Vazquez@acs-inc.com
<mailto:Jorge.Vazquez@acs-inc.com> >:
But, I think if you have some routes in the BGP table under RIB-failure,
those routes are not advertised to the neighbors. So you may not have full
reachability.
Jorge
_____
From: Carlos Alberto Trujillo Jimenez
[mailto:carlos.trujillo.jimenez@gmail.com
<mailto:carlos.trujillo.jimenez@gmail.com> ]
Sent: Friday, March 07, 2008 6:52 AM
To: Vazquez, Jorge
Cc: ccie forum
Subject: Re: BGP Table on the Lab Exam
Jorge.
Adding one more thing.
The presence of a rib-failure and the removing of that, depends of what is
asked to do in the question.
If the question states FULL REACHABILITY with rib-failure works fine.
but if the question states PRESENT IN THE ROUTING TABLE VIA BGP. You may
adjust some configurations as stated in my last mail, to let it work.
2008/3/7, Carlos Alberto Trujillo Jimenez <carlos.trujillo.jimenez@gmail.com
<mailto:carlos.trujillo.jimenez@gmail.com> >:
Hi Jorge.
A Rib Failure happens when a prefix is present in the bgp table, as well as
in the routing, means the router recibes the same prefix via IBGP as well as
ANY IGP (OSPF, RIP, EIGRP).
According to the administrative distance ANY IGP is prefered over any IBGP
ROUTE. Thats why the route is still present in the routing table, but
learned via any of the IGP you are using in your network.
If you have a RIB-FAILURE you can test it and it must work fine, you must
have reachability to that prefix.
From the BGP point of view, that route present in the bgp table (as
RIB-FAILURE) is still propagated via bgp to its neighbors.
if you want to remove the RIB-FAILURE in your bgp table you may adjust the
ADMIN DISTANCE of the IGP to be higher than the IBGP or may REDUCE the IBGP
admin distance to be lower than the IGP.
cheers.
2008/3/7, Vazquez, Jorge <Jorge.Vazquez@acs-inc.com
<mailto:Jorge.Vazquez@acs-inc.com> >:
Any advice or comment about this? I would like to know what is correct
solution when a RIB-failure appears, cause trying to fix that may impact the
routing in all the network topology and maybe it may not be necessary.
Jorge
_____
From: Vazquez, Jorge
Sent: Thursday, March 06, 2008 10:29 AM
To: ccie forum
Subject: BGP Table on the Lab Exam
I have completed some IE labs in the last days, I have one question about
the BPG table, in case I get some routes with RIB-failure, do I have to fix
that or is that ok to have some routes on RIB-failure?
Regards,
Jorge
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