From: kasturi cisco (kasturi_cisco@xxxxxxxxxxx)
Date: Wed Jul 24 2002 - 15:44:17 GMT-3
Hunt,
U may have used the ip route (static routes)to loopback of RTB and RTC on
RTA for load balancing. In that case may be the static route goes into the
IP table for RTD and shows up ur next hop as RTA. Have u got redistribute
static on RTa ? or may be static routes point to the serial interface of RTA
for the 172.17.0.0 net on RTA ?
Am i making sense here ? that looks surprising. Let me think further ?
Let me know.Can u post ur configs.
kasturi.
>From: Hunt Lee <ciscoforme3@yahoo.com.au>
>Reply-To: Hunt Lee <ciscoforme3@yahoo.com.au>
>To: ccielab@groupstudy.com
>Subject: BGP Next Hop?
>Date: Thu, 25 Jul 2002 00:48:31 +1000 (EST)
>
>Can someone please clarify this for me?
>
> RTB
> /
>RTD -- RTA
> \
> RTC
>
>RTB & RTC are both in AS1
>RTA & RTD are both in AS2
>
>RTD's interface (connecting to RTA) :- 25.25.25.1
>RTA's interface (back to RTD) :- 25.25.25.2
>RTA's interface (to RTB) :- 10.1.1.1
>RTB's interface (back to RTA) :- 10.1.1.2
>RTA's interface (to RTC) :- 10.1.2.1
>RTC's interface (back to RTA) :- 10.1.2.2
>
>RTA is connected with RTB & C with Serial connections, while
>connecting with RTD with Ethernet
>
>Both RTB & RTC are advertising a network 172.17.1.0/24 (directly
>connected via Eth from both routers). Also, in order to do BGP load
>balancing to that network, I have use the "maximum-paths 6" command
>at RTA.
>
>RouterA#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
>B 172.17.1.0 [20/0] via 10.1.2.2, 00:36:24
> [20/0] via 10.1.1.2, 00:36:18
> 25.0.0.0/24 is subnetted, 1 subnets
>C 25.25.25.0 is directly connected, Ethernet0
> 10.0.0.0/30 is subnetted, 2 subnets
>C 10.1.2.0 is directly connected, Serial1
>C 10.1.1.0 is directly connected, Serial0
>RouterA#
>
>Ok, here's what I am very confused. When I lookup RTD's BGP table
>(shown below), for the BGP route 172.17.1.0/24, instead of the
>Next-hop being 10.1.1.2 or 10.1.2.2, it is 25.25.25.2. Since I
>thought that in EBGP peering, the next hop is the IP address of the
>neighbor that announced the route, while IBGP peering preserve the
>Next-hop attribute learned from EBGP peers. So in the case, if I
>haven't use next-hop-self on RTA, I would think the Next-Hop in RTD's
>BGP table would be either 10.1.1.2 or 10.1.2.2....
>
>RouterD#sh ip bgp
>BGP table version is 9, local router ID is 25.25.25.1
>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 25.25.25.2 100 0 1 i
>*>i10.1.2.0/30 25.25.25.2 100 0 1 i
>*>i25.25.25.0/24 25.25.25.2 0 100 0 i
>*>i172.17.1.0/24 25.25.25.2 0 100 0 1 i
>RouterD#
>
>
>RouterA#sh ip bgp
>BGP table version is 12, local router ID is 25.25.25.2
>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 10.1.2.2 0 1 i
>* 10.1.1.2 0 0 1 i
>*> 10.1.2.0/30 10.1.1.2 0 1 i
>* 10.1.2.2 0 0 1 i
>*> 25.25.25.0/24 0.0.0.0 0 32768 i
>*> 172.17.1.0/24 10.1.1.2 0 0 1 i
>* 10.1.2.2 0 0 1 i
>RouterA#
>
>
>RouterB#sh ip bgp
>BGP table version is 7, local router ID is 172.17.1.1
>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
>*>i10.1.2.0/30 172.17.1.2 0 100 0 i
>* i25.25.25.0/24 10.1.2.1 0 100 0 2 i
>*> 10.1.1.1 0 0 2 i
>* i172.17.1.0/24 172.17.1.2 0 100 0 i
>*> 0.0.0.0 0 32768 i
>RouterB#
>
>
>RouterC#sh ip bgp
>BGP table version is 7, local router ID is 172.17.1.2
>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
>*>i10.1.1.0/30 172.17.1.1 0 100 0 i
>*> 10.1.2.0/30 0.0.0.0 0 32768 i
>* i25.25.25.0/24 10.1.1.1 0 100 0 2 i
>*> 10.1.2.1 0 0 2 i
>* i172.17.1.0/24 172.17.1.1 0 100 0 i
>*> 0.0.0.0 0 32768 i
>RouterC#
>
>
>Thanks
>Hunt Lee
>
>http://www.sold.com.au - SOLD.com.au
>- Find yourself a bargain!
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:42 GMT-3