rip, bgp & default

From: Volkov, Dmitry (IDS Canada) (dmitry_volkov@ca.ml.com)
Date: Sun Jul 13 2003 - 18:51:22 GMT-3


http://www.cisco.com/en/US/tech/tk365/tk554/technologies_tech_note09186a0080
094374.shtml
<http://www.cisco.com/en/US/tech/tk365/tk554/technologies_tech_note09186a008
0094374.shtml>
Note: In IOS release 12.0T and later, RIP does not advertise the default
router if the route is not learned via RIP. Therefore, it may be necessary
to redistribute the route into RIP, or use the default-information originate
command.
 
ibgp--(170.70.200.1)R1(170.70.10.1)---rip---(.16)R16 (IOS 12.1.5 T14)
 
 
1) R1 gets default via IBGP; R1 doesn't redistr BGP to RIP but has
default-information originate command.
R1 doesn't advertise 0.0.0.0 network to R16
 
r1#
   Network Next Hop Metric LocPrf Weight Path
*>i0.0.0.0 170.70.200.4 0 100 0 444 ?
r1#sh ip ro 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 543", distance 200, metric 0, candidate default path
  Tag 444, type internal
  Last update from 170.70.200.4 00:00:00 ago
  Routing Descriptor Blocks:
  * 170.70.200.4, from 66.3.3.3, 00:00:00 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1

r16#sh ip ro 0.0.0.0
% Network not in table
 
2) R1 does BGP redistr to RIP - default goes to R16
 
r16#sh ip ro 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "rip", distance 120, metric 2, candidate default path
  Redistributing via rip
  Last update from 170.70.10.1 on Ethernet0, 00:00:00 ago
  Routing Descriptor Blocks:
  * 170.70.10.1, from 170.70.10.1, 00:00:00 ago, via Ethernet0
      Route metric is 2, traffic share count is 1
 
3) Shut BGP neighbor - default goes to R16 !!!
  
r1(config)#router bgp 543
r1(config-router)#neighbor 66.3.3.3 shu
 
r16#sh ip ro 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "rip", distance 120, metric 1, candidate default path
  Redistributing via rip
  Last update from 170.70.10.1 on Ethernet0, 00:00:00 ago
  Routing Descriptor Blocks:
  * 170.70.10.1, from 170.70.10.1, 00:00:00 ago, via Ethernet0
      Route metric is 1, traffic share count is 1
 
Any explanations ??



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