BGP advertise-best-external on RR

Wed Sep 2 04:12:45 UTC 2015

There's no such thing as free lunch right :). If BGP Add-Path or
Diverse-Path isn't option for you then as you mentioned Internet VRF with
different RD is the third option but you have to understand the
implications here as well around increase in % of memory. Another option
could be to bypass the RR's and just fully mesh it.

But if none of the above is an option, then you may have to do some
unnatural act to solve it.

On Tue, Sep 1, 2015 at 7:51 AM, Mohamed Kamal <mkamal at noor.net> wrote:

> Hi,
>
> Diverse-path will only send the second best path, and in my case I have
> three routes not two. In addition to that, every PE will have to peer with
> the RR via a second session (on the same RR, as I will not deploy a new
> standalone shadow RR) and this will increase the BGP sessions to the double.
>
> Add-path will have a network-wide IOS upgrade for this BGP capability to
> be supported which is not viable now.
>
> So, is there any other recommendation other than the internet VRF with
> different RDs solution?
>
> Regards,
>
> Mohamed Kamal
> Core Network Sr. Engineer
>
> On 8/25/2015 11:37 AM, Jeff Tantsura wrote:
>
>> Hi,
>>
>> In your case I¹d recommend to use diverse path, due to its simplicity and
>> non disruptive deployment characteristics.
>> As you know - diverse path requires additional BGP session per additional
>> (second, next, etc) path, in most cases not a problem, however mileage
>> might vary.
>>
>> To my memory, in Cisco land - it has only been implemented in IOS, not XR,
>> please check.
>>
>> Cheers,
>> Jeff
>>
>>
>>
>>
>> -----Original Message-----
>> From: Diptanshu Singh <diptanshu.singh at gmail.com>
>> Date: Monday, August 24, 2015 at 10:53 PM
>> To: Mohamed Kamal <mkamal at noor.net>
>> Cc: "nanog at nanog.org" <nanog at nanog.org>
>> Subject: Re: BGP advertise-best-external on RR
>>
>> Yes . In the case of diverse path , shadow route reflector will be the
>>> one wherever  you enable commands to trigger diverse path computation.
>>>
>>> Good thing with diverse path is that the RR-Clients don't have to have
>>> any support but bad thing is that it can only reflect One additional
>>> best-path( second best path ) .
>>>
>>> Sent from my iPhone
>>>
>>> On Aug 24, 2015, at 2:31 PM, Mohamed Kamal <mkamal at noor.net> wrote:
>>>>
>>>> It's only supported on the 15.2(4)S and later not the SRE train. I
>>>> might consider an upgrade.
>>>>
>>>> One more question regarding this, can you configure the RR to be the
>>>> main and shadow RR?
>>>>
>>>> Mohamed Kamal
>>>> Core Network Sr. Engineer
>>>>
>>>> On 8/24/2015 9:16 PM, Diptanshu Singh wrote:
>>>>> BGP Add-Path might be your friend . You can look at diverse-path as
>>>>> well .
>>>>>
>>>>
>>
>