From: Peter van Oene (pvo@xxxxxxxxxxxx)
Date: Thu Jul 11 2002 - 09:41:00 GMT-3
If RB has a loopback, it will use that as the next hop and then its not so
nice.
At 05:37 PM 7/10/2002 -0700, ccie candidate wrote:
> i think what you did is nice ..when RB advertises 172.17.1.0 subnet to
> RC , it will be propagated to RC with next hop of RB , so RC will be able
> to add this network into the routing table ( because the two conditions
> are satisfied , no sync and next hop ,)
>as long as this subnet appears in RC routing table , the router again will
>be able to push the 199.172.1.0 into its routing table , because no sync
>and now the next hop is known ( 172.17.1.0 ) which is RA address .
>
>interesting :)
>
>
>
>--
>
>On Wed, 10 Jul 2002 23:53:45
> Hunt Lee wrote:
> >Hi Group,
> >
> >199.172.1.0 / 24 --- RTA --- RTB --- RTC
> >
> >RTA's interface - 172.17.1.2 (connecting to RTB)
> >RTB's interface - 172.17.1.1 (connecting to RTA)
> >RTB's interface - 10.1.1.1 (connecting to RTC)
> >RTC's interface - 10.1.1.2 (connecting to RTB)
> >
> >RTA is in AS 1
> >RTB & RTC are both in AS 2
> >
> >I understand that for a router to learn and install an IBGP route
> >from an IBGP neighbor, it will need either "no sync" command or
> >learnt via any IGP. But for the BGP route's next-hop reachability, I
> >have searched on Cisco books & CCO website, but they only said either
> >advertised the next-hop to the IBGP router (in this case, RTC) with
> >IGP routes, or use "next-hop-self" command (on RTB). However, I
> >found that if I advertise the next-hop reachability (the
> >172.17.1.0/24 subent) via BGP's network command, it would also work.
> >Is this ok to use?? Is there any gotcha on this?? I just thought it
> >is pretty handy to just use BGP, without relying on any IGP.
> >
> >
> >RouterB#sh ip bgp
> >BGP table version is 4, local router ID is 192.168.0.1
> >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
> >*> 10.1.1.0/30 0.0.0.0 0 32768 i
> >*> 172.17.1.0/24 0.0.0.0 0 32768 i
> >*> 199.172.1.0 172.17.1.2 0 0 1 i
> >
> >RouterB#sh 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 not set
> >
> > 172.17.0.0/24 is subnetted, 1 subnets
> >C 172.17.1.0 is directly connected, Ethernet0
> > 10.0.0.0/30 is subnetted, 1 subnets
> >C 10.1.1.0 is directly connected, Serial0
> >B 199.172.1.0/24 [20/0] via 172.17.1.2, 01:34:38
> >C 192.168.0.0/24 is directly connected, Loopback0
> >RouterB#
> >
> >And at RTC, it would be able to reach 199.172.1.0 /24 via next hop of
> >172.17.1.2, which in turn is reached via 10.1.1.1.
> >
> >RouterC#sh ip bgp
> >BGP table version is 4, local router ID is 172.16.3.1
> >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
> >*>i10.1.1.0/30 10.1.1.1 0 100 0 i
> >*>i172.17.1.0/24 10.1.1.1 0 100 0 i
> >*>i199.172.1.0 172.17.1.2 0 100 0 1 i
> >
> >RouterC#sh 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, * -
> >candidate
> >default
> > U - per-user static route, o - ODR
> >
> >Gateway of last resort is not set
> >
> > 172.17.0.0/24 is subnetted, 1 subnets
> >B 172.17.1.0 [200/0] via 10.1.1.1, 00:26:57
> > 172.16.0.0/24 is subnetted, 2 subnets
> >C 172.16.2.0 is directly connected, Loopback1
> >C 172.16.3.0 is directly connected, Loopback0
> > 10.0.0.0/30 is subnetted, 1 subnets
> >C 10.1.1.0 is directly connected, Serial0
> >B 199.172.1.0/24 [200/0] via 172.17.1.2, 00:25:57
> >RouterC#
> >
> >
> >Any ideas will be greatly appreciated.
> >
> >Thanks!!!
> >
> >H.
> >
> >
> >
> >http://www.sold.com.au - SOLD.com.au
> >- Find yourself a bargain!
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