From: Koen Zeilstra (koen@koenzeilstra.com)
Date: Thu Oct 18 2007 - 02:59:37 ART
Correct. The conditions are never met for ACL 10.
I have labbed the original and this solution up, no AND just OR.
Quoting Balmik Soin <balmik@staff.iinet.net.au>:
> Unless I'm reading it wrong, it looks like the config is wrong, which is
> causing confusion.
>
> Your Loopback2 is 2.2.2.0/24, but access-list 10 is matching 2.0.0.0
>
> Thus, the conditions for access-list 10 are never met. Only access-list
> 20 is met, and when you shutdown loopback20, it no longer is, causing
> the route to be withdrawn.
>
> If you want to test this, either change Loopback2 to be a 2.0.0.0
> subnet, change access-list 10 to match 2.2.2.0, or just try shutting
> down Loopback2 instead of Loopback20 and see what happens.
>
> - Balmik.
>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
>> Bob Sinclair
>> Sent: Thursday, 18 October 2007 5:42 AM
>> To: Saul Arjona
>> Cc: ccielab@groupstudy.com
>> Subject: Re: conditional default advertising in BGP with multiple
> routes
>> to monitor
>>
>> Saul Arjona wrote:
>> >> Bob,
>> >>
>> >
>> >
>> >
>> > I labbed it up and it is not working as a functional AND but as a
>> functional
>> > OR as Koen mentioned. So as long as one of the routes is still in
> the
>> > routing table we will still advertise the default route, it will
> stop
>> > advertising it only if both routes are out of the routing table.
>> >
>> > regards,
>> > -Saul
>> >
>> > You might want to lab this up. When I do a conditional default
> using
>> >
>> >> RIP or BGP the router in fact implements the match as an AND
> function.
>> >> In other words, BOTH must be in the table. Here is an example
> with
>> BGP:
>> >>
>> >> interface Loopback2
>> >> ip address 2.2.2.2 255.255.255.0
>> >> !
>> >> interface Loopback20
>> >> ip address 20.0.0.1 255.0.0.0
>> >> shutdown
>> >> router bgp 200
>> >> no synchronization
>> >> bgp log-neighbor-changes
>> >> neighbor 172.16.25.5 remote-as 500
>> >> neighbor 172.16.25.5 default-originate route-map CONDITIONAL
>> >> no auto-summary
>> >> access-list 10 permit 2.0.0.0
>> >> access-list 20 permit 20.0.0.0
>> >> !
>> >> route-map CONDITIONAL permit 10
>> >> match ip address 10 20
>> >>
>> >>
>> Hi Saul,
>>
>> It for this reason that I always tell students "believe none of what
> you
>> hear and only half of what you see". The result of any test will
>> depend on the complete context and exact procedures. Above, I have
>> shown you what I consider to be the relevant config on the sending
>> router. Below you will see the debug of what happens when ONLY ONE
> of
>> the loopbacks is shut:
>>
>> R2#sh ip int brief | excl unass
>> Interface IP-Address OK? Method
>> Status Protocol
>> Serial0/0 172.16.123.2 YES NVRAM administratively
>> down down
>> Serial1/0 172.16.25.2 YES NVRAM
>> up up
>> Loopback2 2.2.2.2 YES manual
>> up up
>> Loopback20 20.0.0.1 YES manual
>> up up
>>
>>
>> R2(config)#int loop20
>> R2(config-if)#shut
>> R2(config-if)#
>> *Oct 16 04:21:10.321: BGP(0): 172.16.25.5 send unreachable 0.0.0.0/0
>> <<<<<<<NOTE
>> *Oct 16 04:21:10.321: BGP(0): 172.16.25.5 enqueued default-originate
>> update
>> R2(config-if)#
>> *Oct 16 04:21:12.317: %LINK-5-CHANGED: Interface Loopback20, changed
>> state to administratively down
>> *Oct 16 04:21:13.317: %LINEPROTO-5-UPDOWN: Line protocol on Interface
>> Loopback20, changed state to down
>> R2(config-if)#no shut
>> R2(config-if)#
>> *Oct 16 04:21:17.413: BGP(0): 172.16.25.5 enqueued default-originate
>> update <<<<< NOTE
>> R2(config-if)#
>> *Oct 16 04:21:19.405: %LINK-3-UPDOWN: Interface Loopback20, changed
>> state to up
>> *Oct 16 04:21:20.405: %LINEPROTO-5-UPDOWN: Line protocol on Interface
>> Loopback20, changed state to up
>> R2(config-if)#
>>
>>
>> It sure looks to me like when I shut ONE of the loopbacks, withdrawing
>> ONLY ONE of the required routes, BGP withdraws the default. And when
> I
>> no-shut that interface it is re-advertised. To me, this pretty
> clearly
>> says that the router is implementing the route-map as an AND.
>>
>> What am I missing??
>>
>> Maybe you could share some of the context that led to your conclusion.
>>
>> --
>>
>>
>> Bob Sinclair CCIE 10427 CCSI 30427
>> www.netmasterclass.net
>>
>>
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