From: david@gotimmons.com
Date: Sun Mar 02 2008 - 03:37:38 ARST
Hi,
You might do a search for bgp best path selection. The admin distance is about about seventh in the decision process.
Sent from my BlackBerry. wireless device
-----Original Message-----
From: "Greg Wendel" <gwendel@gmail.com>
Date: Sat, 1 Mar 2008 20:27:01
To:"Joseph Brunner" <joe@affirmedsystems.com>
Cc:"Cisco certification" <ccielab@groupstudy.com>
Subject: Re: IP routing table preemption. While working on Joe Brunner's
lab.
Joe,
Thanks for the link, I had never heard of this BGP issue prior to your
link. You are correct, the EBGP of 20 should win, but as your link shows it
doesn't. In the Network Pro article the solution was to increase the weight
of the routes or increase the admin distance of EIGRP to 200.
In my case if I cleared the routes in EIGRP they would no longer preempt the
bgp routes for the same prefixes, but if they were existing before the BGP
peer started then they would remain in the routing table.
Thanks again for your great lab idea.
FYI,
Here is the lab I am using so there might be other reasons for this.
R1 connection to R3 EIGRP
R1 connection to R4 EBGP
R3 conection to R1 EIGRP
R3 connection to R2 OSPF
R2 connection to R3 EIGRP
R2 connection to R4 RIP
R4 connection to R2 RIP
R4 connection to R1 EBGP
Mutual redistribution everywhere
I am also in process of adding another router R5 between R2 and R3 to add
complexity with the OSPF and RIP redistribution.
On Sat, Mar 1, 2008 at 7:57 PM, Joseph Brunner <joe@affirmedsystems.com>
wrote:
> >NO bgp routes even though admin distance of 200 wins.
>
> Wouldn't EIGRP be preferred, with an AD of 90 or 170? Didn't you mean
>
> NO bgp routes even though admin distance of 20 wins.
>
> Your only BGP neighbor is in a different AS, hence EBGP when these routes
> come back? Yes?
>
> I think your running into the same EXACT fleet of Romulans we encountered
> last year check this link, and look at " Narayan's" first response...
>
>
> http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20I
>
> nfrastructure&topic=WAN%2C%20Routing%20and%20Switching&CommCmd=MB%3Fcmd%3Ddi<http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=WAN%2C%20Routing%20and%20Switching&CommCmd=MB%3Fcmd%3Ddi>
> splay_location%26location%3D.1ddec668
>
> -Joe
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Greg
> Wendel
> Sent: Saturday, March 01, 2008 6:07 PM
> To: Cisco certification
> Subject: IP routing table preemption. While working on Joe Brunner's lab.
>
> I am following Joe B's advice to setup a bunch of routers and redistribute
> them all over the place and I found something interesting.
>
> Is the below expected behavior. I understand the end result but I am
> curious if this is expected behavior. While doing labs I always reset the
> processes clear bgp soft, clear ip route * etc to make sure my changes
> work
> as I expect.
>
> executive summary: BGP will not preempt EIGRP routes unless the EIGRP
> neighbor is cleared and vice versa.
>
> Here is the relevant config:
>
> router eigrp 100
> redistribute bgp 14 route-map BGP2EIGRP
> network 10.13.13.1 0.0.0.0
> network 10.213.213.213 0.0.0.0
> default-metric 1 1 1 1 1
> no auto-summary
> eigrp router-id 1.1.1.1
> !
> router bgp 14
> no synchronization
> bgp router-id 1.1.1.1
> bgp log-neighbor-changes
> network 10.14.14.0 mask 255.255.255.0
> network 10.214.214.214 mask 255.255.255.255
> redistribute eigrp 100 metric 100
> neighbor 10.14.14.4 remote-as 41
> no auto-summary
>
> Here is the interesting part
>
> Rack1R1(tcl)# sh ip route summ
> IP routing table name is Default-IP-Routing-Table(0)
> IP routing table maximum-paths is 16
> Route Source Networks Subnets Overhead Memory (bytes)
> connected 0 4 288 544
> static 0 0 0 0
> *eigrp 100 0 13 936 1768*
> bgp 14 0 0 0 0
> External: 0 Internal: 0 Local: 0
> internal 1 1156
> Total 1 17 1224 3468
>
> Enter configuration commands, one per line. End with CNTL/Z.
> Rack1R1(config)#router bgp 14
>
> Rack1R1(config-router)#no neighbor 10.14.14.4 shu
>
> Rack1R1(config-router)#end
>
> Rack1R1(tcl)#sh ip bgp
> *Mar 1 01:31:28.399: %BGP-5-ADJCHANGE: neighbor 10.14.14.4 Up
> *Mar 1 01:31:29.079: %SYS-5-CONFIG_I: Configured from console by console
> Rack1R1(tcl)#sh ip bgp summ
> BGP router identifier 1.1.1.1, local AS number 14
> BGP table version is 96, main routing table version 96
> 17 network entries using 1989 bytes of memory
> 34 path entries using 1768 bytes of memory
> 7/3 BGP path/bestpath attribute entries using 868 bytes of memory
> 1 BGP AS-PATH entries using 24 bytes of memory
> 0 BGP route-map cache entries using 0 bytes of memory
> 0 BGP filter-list cache entries using 0 bytes of memory
> BGP using 4649 total bytes of memory
> BGP activity 17/0 prefixes, 101/67 paths, scan interval 60 secs
>
> Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
> State/PfxRcd
> 10.14.14.4 4 41 116 117 96 0 0 00:00:02
> 17
> Rack1R1(tcl)#sh ip route bgp
>
> Rack1R1(tcl)#
>
> NO bgp routes even though admin distance of 200 wins.
>
> But then if I do a clear ip eigrp neighbors
>
>
> Rack1R1(tcl)# sh ip route summ
> IP routing table name is Default-IP-Routing-Table(0)
> IP routing table maximum-paths is 16
> Route Source Networks Subnets Overhead Memory (bytes)
> connected 0 4 288 544
> static 0 0 0 0
> eigrp 100 0 0 0 0
> *bgp 14 0 13 936 1768
> * External: 13 Internal: 0 Local: 0
> internal 1 1156
> Total 1 17 1224 3468
> Rack1R1(tcl)#
>
>
> --
> Gregory Wendel
> Springfield VA, 22153
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
-- Gregory Wendel Springfield VA, 22153
This archive was generated by hypermail 2.1.4 : Tue Apr 01 2008 - 07:53:51 ART