Re: BGP Trick: Peering Double Default Route

Hi Jose,

I don't understand why it is not working with default routes at each end.

Sud

Sent from my iPad

On Jul 18, 2012, at 5:29 PM, Raghava Rao <raghava.rao85_at_gmail.com> wrote:

> Good article to further read on
>
> http://gandikitchen.net/post/2011/06/20/When-Null0-and-BGP-May-Cause-Problems
>
>
>
> //RR
>
> On 18 July 2012 17:14, Jose Jara <jjarafiz_at_gmail.com> wrote:
>
>> Hi mates,
>>
>> I am just writing to put here a trick that I have found out after doing
>> some testing in BGP peering. Let4s say we have two routers (R1&R2) directly
>> connected and they're going to establish an eBGP session between their
>> loopbacks.They will use update-source with the loopback and
>> disable-connected check. However, the reachability is via a default route
>> in each router, therefore, the BGP session can not be established:
>>
>> BGP: *2.2.2.2 active open failed - no route to peer*, open active delayed
>> 32091ms (35000ms max, 28% jitter)
>>
>> What I thought was, how could they go ahead and establish the session
>> without changing the routing? What if I install a route to the loopback
>> pointing to null 0 to bypass the BGP check and then, remove it ?
>> I tested it and surprisingly it worked! Look at that:
>>
>> *R1(config)#ip route 2.2.2.2 255.255.255.255 null 0
>> *R1(config)#
>> *Mar 1 00:05:11.751: BGP: 2.2.2.2 open active, local address 1.1.1.1
>> *R1(config)#no ip route 2.2.2.2 255.255.255.255 null 0
>> *R1(config)#
>> *Mar 1 00:05:17.843: BGP: 2.2.2.2 went from Active to OpenSent
>> *Mar 1 00:05:17.847: BGP: 2.2.2.2 sending OPEN, version 4, my as: 100,
>> holdtime 180 seconds
>> *Mar 1 00:05:17.851: BGP: 2.2.2.2 send message type 1, length (incl.
>> header) 45
>> *Mar 1 00:05:17.903: BGP: 2.2.2.2 rcv message type 1, length (excl.
>> header) 26
>> *Mar 1 00:05:17.907: BGP: 2.2.2.2 rcv OPEN, version 4, holdtime 180
>> seconds
>> *Mar 1 00:05:17.907: BGP: 2.2.2.2 rcv OPEN w/ OPTION parameter len: 16
>> *Mar 1 00:05:17.907: BGP: 2.2.2.2 rcvd OPEN w/ optional parameter type 2
>> (Capability) len 6
>> *Mar 1 00:05:17.907: BGP: 2.2.2.2 OPEN has CAPABILITY code: 1, length 4
>> *Mar 1 00:05:17.907: BGP: 2.2.2.2 OPEN has MP_EXT CAP for afi/safi: 1/1
>> *Mar 1 00:05:17.911: BGP: 2.2.2.2 rcvd OPEN w/ optional parameter type 2
>> (Capability) len 2
>> *Mar 1 00:05:17.911: BGP: 2.2.2.2 OPEN has CAPABILITY code: 128, length 0
>> *Mar 1 00:05:17.911: BGP: 2.2.2.2 OPEN has ROUTE-REFRESH capability(old)
>> for all address-families
>> *Mar 1 00:05:17.911: BGP: 2.2.2.2 rcvd OPEN w/ optional parameter type 2
>> (Capability) len 2
>> *Mar 1 00:05:17.911: BGP: 2.2.2.2 OPEN has CAPABILITY code: 2, length 0
>> *Mar 1 00:05:17.915: BGP: 2.2.2.2 OPEN has ROUTE-REFRESH capability(new)
>> for all address-families
>> BGP: 2.2.2.2 rcvd OPEN w/ remote AS 200
>> *Mar 1 00:05:17.915: BGP: 2.2.2.2 went from OpenSent to OpenConfirm
>> *Mar 1 00:05:17.915: BGP: 2.2.2.2 went from OpenConfirm to Established
>> *Mar 1 00:05:17.915: %BGP-5-ADJCHANGE: neighbor 2.2.2.2 Up
>>
>> Just for fun!
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Thu Jul 19 2012 - 21:00:15 ART