IP routing table preemption. While working on Joe Brunner's

From: Greg Wendel (gwendel@gmail.com)
Date: Sat Mar 01 2008 - 21:06:45 ARST


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


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