From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Mon Jul 29 2002 - 00:21:21 GMT-3
Ted,
Based on the scenario you pointed out on CCO in the bgp design
guide(CIDR1), there is
no other way to meet the requirements. The key issue here is getting the
160.0.0.0 route advertised
by RtrB(AS200) to the neighboring peer, RtrC(in AS300).
The problem as shown in the example, is that bgp natively performs
auto-summarization, and the
network route(160.10.0.0) in question will remain the same. There is no
other way to generate a
route for the 160.0.0.0 without a "static route" to null0 as the example
depicts. Furthermore, even if
the "aggregate-address" or "network" commands are used this will not work
because bgp will
also need to know of the route(on the 160.0.0.0 network) before it could be
advertised.
However, this would require an interface to be configured which technically
will
not work due to the overlap on subnets which is why the two options
identified was used.
HTH
Nigel
----- Original Message -----
From: "Bruce Williams" <bruce@williamsnetworking.com>
To: "Ted McDermott" <tedmcdermott@yahoo.com>; <ccielab@groupstudy.com>
Sent: Sunday, July 28, 2002 9:31 PM
Subject: RE: BGP - Suppressing Specific Routes
> The "aggregate address x.x.x.x y.y.y.y suppress-map map name" worked.
Router
> 3 is eBGP peer with R5. R3 is advertising 3 loopbacks 200.200.200.0 /24,
> 200.200.201.0 /24 and 200.200.202.0 /24. I aggregated them into
200.200.0.0
> 255.255.0.0 and suppressed all of the three more specific routes with a
> route map. I pasted R3's configs and the "sh ip bgp" from R5.
>
> !
> hostname r3
> !
> !
> ip subnet-zero
> no ip domain-lookup
> !
> !
> !
> interface Loopback900
> ip address 200.200.200.1 255.255.255.0
> no ip directed-broadcast
> !
> interface Loopback901
> ip address 200.200.201.1 255.255.255.0
> no ip directed-broadcast
> !
> interface Loopback902
> ip address 200.200.202.1 255.255.255.0
> no ip directed-broadcast
> !
> interface Ethernet0
> ip address 172.16.50.3 255.255.255.0
> no ip directed-broadcast
> !
> interface Ethernet1
> ip address 172.16.35.3 255.255.255.0
> no ip directed-broadcast
> !
> interface Serial0
> no ip address
> no ip directed-broadcast
> no ip mroute-cache
> shutdown
> no fair-queue
> !
> interface Serial1
> no ip address
> no ip directed-broadcast
> shutdown
> !
> router bgp 1
> network 172.16.0.0
> network 200.200.200.0
> network 200.200.201.0
> network 200.200.202.0
> aggregate-address 200.200.0.0 255.255.0.0 suppress-map suppres
> neighbor 172.16.35.5 remote-as 2
> !
> ip classless
> !
> access-list 99 permit 200.200.200.0 0.0.0.255
> access-list 99 permit 200.200.201.0 0.0.0.255
> access-list 99 permit 200.200.202.0 0.0.0.255
> route-map suppres permit 10
> match ip address 99
> !
> route-map suppres deny 20
> !
> !
> line con 0
> exec-timeout 0 0
> transport input none
> line aux 0
> line vty 0 4
> !
> end
>
>
> r5#sh ip bgp
> BGP table version is 4, local router ID is 172.16.35.5
> 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
> *> 172.16.0.0 0.0.0.0 0 32768 i
> * 172.16.35.3 0 0 1 i
> *> 200.200.0.0/16 172.16.35.3 0 1 i
> r5#
>
>
> Bruce
>
>
>
>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Ted McDermott
> Sent: Sunday, July 28, 2002 4:23 PM
> To: ccielab@groupstudy.com
> Subject: BGP - Suppressing Specific Routes
>
>
> In Cisco - BGP Case Studies Section 4
> (http://www.cisco.com/warp/customer/459/16.html), the
> author gives two solutions for suppressing the
> specific local route 160.10.0.0 while advertising an
> aggregate 160.0.0.0 route. Since an "aggregate
> summary-only" command would not suppress the more
> specific local route, the author gives two options,
> both of which involve creating a static route to
> null0. Neither of these would be acceptable if static
> routes are not allowed. Is there any solution for this
> which avoids static routes?
>
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:47 GMT-3