From: Hunt Lee (huntl@xxxxxxxxxxxxxxxxx)
Date: Sat Jul 13 2002 - 22:26:42 GMT-3
Thanks for you guys explanation for this one.
My understanding is this:-
If the Loopback interface added on RTB is only propagated out via BGP, but
is not used for BGP neighbor relationship (with RTC), then my config is
fine... there is no need for adding it into IGP (between RTB & RTC) or add
static route to it (at RTC), since the only thing that it will affect is
RTB's BGP Router ID.
However, if the Loopback interface added on RTB is used for BGP neighbor
relationship (with RTC) - with the "neighbor x.x.x.x update-source Loopback
0" command, then one must add it into IGP (between RTB & RTC) or add static
route to it (at RTC).
Regards,
H.
-----Original Message-----
From: Peter van Oene [mailto:pvo@usermail.com]
Sent: Friday, 12 July 2002 8:31 AM
To: Omer Ansari
Cc: ccielab@groupstudy.com
Subject: Re: next-hop reachability
Doing that still will not allow RC to resolve the IGP nexthop for the
route(s). You'd need to put the loopback on Rb into an IGP or add statics
on Rc
At 05:46 PM 7/11/2002 +0100, you wrote:
>Unless you add the loopback interface as a network statement into BGP.
>
>but then you could avoid the two commands, and extra routes in the route
>table by just using next-hop-self.
>
>On Thu, 11 Jul 2002, Peter van Oene wrote:
>
> > 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!
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:29 GMT-3