From: ccie candidate (ccie1@xxxxxxxxx)
Date: Wed Jul 10 2002 - 21:37:59 GMT-3
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 a
ble to push the 199.172.1.0 into its routing table , because no sync and now th
e 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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