Kevin Dorrell, CCIE #20765

27 Apr 2008

NMC Lab 9.8 BGP

Filed under: BGP — dorreke @ 09:34

Following a posting on DISCUSSiT, I reloaded my configs for Lab 09 to investigate the BGP question.  Here are my notes:

Start with default from FRS:

R3#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 65034", distance 20, metric 0, candidate default path
  Tag 700, type external
  Last update from 172.16.34.7 00:03:25 ago
  Routing Descriptor Blocks:
  * 172.16.34.7, from 172.16.34.7, 00:03:25 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 700
R4#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 65034", distance 20, metric 0, candidate default path
  Tag 700, type external
  Last update from 172.16.34.7 00:03:28 ago
  Routing Descriptor Blocks:
  * 172.16.34.7, from 172.16.34.7, 00:03:28 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 700

Shut down Lo107:

FRS#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
FRS(config)#int Lo107
FRS(config-if)#shut

This is what happens on R3 and R4:

R3#
*Apr  8 17:20:36: RT: del 0.0.0.0 via 172.16.34.7, bgp metric [20/0]
*Apr  8 17:20:36: RT: delete network route to 0.0.0.0
*Apr  8 17:20:36: RT: NET-RED 0.0.0.0/0
*Apr  8 17:20:36: RT: NET-RED 0.0.0.0/0
*Apr  8 17:20:37: RT: SET_LAST_RDB for 0.0.0.0/0
  NEW rdb: is directly connected
*Apr  8 17:20:37: RT: add 0.0.0.0/0 via 0.0.0.0, static metric [250/0]
*Apr  8 17:20:37: RT: NET-RED 0.0.0.0/0
*Apr  8 17:20:37: RT: default path is now 0.0.0.0 via 0.0.0.0
*Apr  8 17:20:37: RT: new default network 0.0.0.0
*Apr  8 17:20:37: RT: NET-RED 0.0.0.0/0
*Apr  8 17:20:37: RT: delete route to 172.16.107.0 via 172.16.34.4, eigrp metric [90/158720]
*Apr  8 17:20:37: RT:
R3#SET_LAST_RDB for 172.16.107.0/24
  OLD rdb: via 172.16.34.4, FastEthernet0/1
*Apr  8 17:20:37: RT: no routes to 172.16.107.0
*Apr  8 17:20:37: RT: NET-RED 172.16.107.0/24
*Apr  8 17:20:37: RT: delete subnet route to 172.16.107.0/24
*Apr  8 17:20:37: RT: NET-RED 172.16.107.0/24
R3#
.Apr 27 10:22:55: RT: recursion error routing 172.16.107.0 - probable routing loop
.Apr 27 10:22:55: RT: del 172.16.0.0/16 via 172.16.107.0, static metric [1/0]
.Apr 27 10:22:55: RT: delete subnet route to 172.16.0.0/16
.Apr 27 10:22:55: RT: NET-RED 172.16.0.0/16
.Apr 27 10:22:55: RT: NET-RED 0.0.0.0/0
R3#
R3#
R3#
R3#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "static", distance 250, metric 0 (connected), candidate default path
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 0, traffic share count is 1

And on R4:

R4#
*Apr  8 17:01:33: RT: del 0.0.0.0 via 172.16.34.7, bgp metric [20/0]
*Apr  8 17:01:33: RT: delete network route to 0.0.0.0
*Apr  8 17:01:33: RT: NET-RED 0.0.0.0/0
*Apr  8 17:01:33: RT: NET-RED 0.0.0.0/0
*Apr  8 17:01:33: RT: SET_LAST_RDB for 0.0.0.0/0
  NEW rdb: is directly connected
*Apr  8 17:01:33: RT: add 0.0.0.0/0 via 0.0.0.0, static metric [250/0]
*Apr  8 17:01:33: RT: NET-RED 0.0.0.0/0
*Apr  8 17:01:33: RT: default path is now 0.0.0.0 via 0.0.0.0
*Apr  8 17:01:33: RT: new default network 0.0.0.0
*Apr  8 17:01:33: RT: NET-RED 0.0.0.0/0
*Apr  8 17:01:34: RT: delete route to 172.16.107.0 via 172.16.34.7, eigrp metric [90/156160]
*Apr  8 17:01:34: RT:
R4#SET_LAST_RDB for 172.16.107.0/24
  OLD rdb: via 172.16.34.7, FastEthernet0/0
*Apr  8 17:01:34: RT: no routes to 172.16.107.0
*Apr  8 17:01:34: RT: NET-RED 172.16.107.0/24
*Apr  8 17:01:34: RT: delete subnet route to 172.16.107.0/24
*Apr  8 17:01:34: RT: NET-RED 172.16.107.0/24
R4#
.Apr 27 10:22:55: RT: recursion error routing 172.16.107.0 - probable routing loop
.Apr 27 10:22:55: RT: del 172.16.0.0/16 via 172.16.107.0, static metric [1/0]
.Apr 27 10:22:55: RT: delete subnet route to 172.16.0.0/16
.Apr 27 10:22:55: RT: NET-RED 172.16.0.0/16
.Apr 27 10:22:55: RT: NET-RED 0.0.0.0/0
R4#

Now bring back Lo107:

FRS(config-if)#
FRS(config-if)#no shut
FRS(config-if)#
*Mar  1 01:13:15: %LINK-3-UPDOWN: Interface Loopback107, changed state to up
*Mar  1 01:13:16: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback107, changed state
 to up

This is R3:

R3#
.Apr 27 10:23:44: RT: SET_LAST_RDB for 172.16.107.0/24
  NEW rdb: via 172.16.34.4
.Apr 27 10:23:44: RT: add 172.16.107.0/24 via 172.16.34.4, eigrp metric [90/158720]
.Apr 27 10:23:44: RT: NET-RED 172.16.107.0/24
R3#
.Apr 27 10:23:46: RT: closer admin distance for 0.0.0.0, flushing 1 routes
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: SET_LAST_RDB for 0.0.0.0/0
  NEW rdb: via 172.16.34.7
.Apr 27 10:23:46: RT: add 0.0.0.0/0 via 172.16.34.7, bgp metric [20/0]
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: default path is now 0.0.0.0 via 172.16.34.7
.Apr 27 10:23:46: RT: new default network 0.0.0.0
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
R3#
.Apr 27 10:23:51: RT: network 172.16.0.0 is now variably masked
.Apr 27 10:23:51: RT: SET_LAST_RDB for 172.16.0.0/16
  NEW rdb: via 172.16.107.0
.Apr 27 10:23:51: RT: add 172.16.0.0/16 via 172.16.107.0, static metric [1/0]
.Apr 27 10:23:51: RT: NET-RED 172.16.0.0/16
.Apr 27 10:23:51: RT: NET-RED 0.0.0.0/0
R3#
Apr 27 10:23:55: RT: NET-RED 0.0.0.0/0
R3#
R3#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 65034", distance 20, metric 0, candidate default path
  Tag 700, type external
  Last update from 172.16.34.7 00:00:24 ago
  Routing Descriptor Blocks:
  * 172.16.34.7, from 172.16.34.7, 00:00:24 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 700

And R4:

R4#
.Apr 27 10:23:44: RT: SET_LAST_RDB for 172.16.107.0/24
  NEW rdb: via 172.16.34.7
.Apr 27 10:23:44: RT: add 172.16.107.0/24 via 172.16.34.7, eigrp metric [90/156160]
.Apr 27 10:23:44: RT: NET-RED 172.16.107.0/24
R4#
.Apr 27 10:23:46: RT: closer admin distance for 0.0.0.0, flushing 1 routes
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: SET_LAST_RDB for 0.0.0.0/0
  NEW rdb: via 172.16.34.7
.Apr 27 10:23:46: RT: add 0.0.0.0/0 via 172.16.34.7, bgp metric [20/0]
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
.Apr 27 10:23:46: RT: default path is now 0.0.0.0 via 172.16.34.7
.Apr 27 10:23:46: RT: new default network 0.0.0.0
.Apr 27 10:23:46: RT: NET-RED 0.0.0.0/0
R4#
.Apr 27 10:23:51: RT: network 172.16.0.0 is now variably masked
.Apr 27 10:23:51: RT: SET_LAST_RDB for 172.16.0.0/16
  NEW rdb: via 172.16.107.0
.Apr 27 10:23:51: RT: add 172.16.0.0/16 via 172.16.107.0, static metric [1/0]
.Apr 27 10:23:51: RT: NET-RED 172.16.0.0/16
.Apr 27 10:23:51: RT: NET-RED 0.0.0.0/0
R4#
Apr 27 10:23:55: RT: NET-RED 0.0.0.0/0
R4#
R4#
R4#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 65034", distance 20, metric 0, candidate default path
  Tag 700, type external
  Last update from 172.16.34.7 00:00:17 ago
  Routing Descriptor Blocks:
  * 172.16.34.7, from 172.16.34.7, 00:00:17 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 700
R4#

Shows BGP route does pre-empt the static.

 

 

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