From: Adam Quiggle (aquiggle@xxxxxxxxx)
Date: Sun Jan 13 2002 - 00:31:39 GMT-3
At 08:57 PM 12/11/01, EA Louie wrote:
>In the configuration of R6, there is no route to R5's ethernet. Therefore, R7
>has no route to the next-hop router, and does not populate it's table. In the
>instructions, you are given the opportunity to add a static default route to
>R5 to get the bgp routes to R7.
>
>I found 2 other ways to accomplish this without that static default route,
>keeping in mind that the static route solution may not be viable in the lab
>exam. Is anyone working that lab and would you like to take a stab at it?
>(all of the solutions are elegant and require very little thought)
-EA
How about:
Solution #1
-----------------------
R6(config)#router bgp 3
R6(config-router)#router bgp neighbor 12.2.1.2 next-hop-self
Solution #2
-----------------------
R6(config)#router ospf 11
R6(config)#network 11.1.0.0 0.0.255.255 area 0
R6(config)#passive-interface ethernet0
Is that what you were thinking? For some reason it never dawned on me that
the default route could be used to determine reachability to the
next-hop. I'm currently playing with this lab and see that the default
route can be used to determine reachability to the next-hop. Here you can
see that both 41.1.1.0/24 and 44.1.1.0/24 installed into the routing table
(auto-summary is turned on)
R7#show ip bgp
BGP table version is 133, local router ID is 7.7.7.7
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i12.0.0.0 12.2.1.1 0 100 0 ?
*>i41.1.1.0/24 11.1.1.5 300 0 2 1 ?
*>i44.1.1.0/24 11.1.1.5 300 0 2 1 i
*>i177.1.0.0 12.2.1.1 0 100 0 ?
R7#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter
area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 12.2.1.1 to network 0.0.0.0
177.1.0.0/16 is variably subnetted, 2 subnets, 2 masks
B 177.1.0.0/16 [200/0] via 12.2.1.1, 00:13:38
C 177.1.1.0/24 is directly connected, Loopback0
41.0.0.0/24 is subnetted, 1 subnets
B 41.1.1.0 [200/0] via 11.1.1.5, 00:05:22
12.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C 12.4.0.0/16 is directly connected, Loopback1
B 12.0.0.0/8 [200/0] via 12.2.1.1, 00:13:38
C 12.2.0.0/16 is directly connected, Serial0
C 12.3.0.0/16 is directly connected, FastEthernet0
44.0.0.0/24 is subnetted, 1 subnets
B 44.1.1.0 [200/0] via 11.1.1.5, 00:05:23
O*E2 0.0.0.0/0 [110/1] via 12.2.1.1, 02:24:44, Serial0
R7#
However this behavior concerns me from a general perspective. How does R7
know that the next-hop just isn't unreachable if it uses the default
route? Can I adjust this behavior? I can't think of anyway to stop this
off the top of my head.
Thanks,
AQ
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:56:26 GMT-3