Best practice for BGP session/ full routes for customer

Nick Hilliard nick at foobar.org
Thu Jul 17 10:24:45 UTC 2014


On 14/07/2014 18:32, Jeff Tantsura wrote:
> BGP to RIB filtering (in any vendor implementation) is targeting RR which
> is not in the forwarding path, so thereĀ¹s no forwarding towards any
> destination filtered out from RIB.
> Using it selectively on a forwarding node is error prone and in case of
> incorrect configuration would result in blackholing.

there are other drawbacks too: the difference in convergence time between <
24k prefixes  and a full dfz is usually going to be large although I
haven't tested this on an me3600x yet.  Also these boxes only have 1G of
memory might be a bit tight as the dfz increases.  For sure, it's already
not enough on a bunch of other vanilla ios platforms.

Nick

> 
> Cheers,
> Jeff
> 
> 
> 
> 
> -----Original Message-----
> From: Mark Tinka <mark.tinka at seacom.mu>
> Organization: SEACOM
> Reply-To: <mark.tinka at seacom.mu>
> Date: Tuesday, July 8, 2014 at 1:56 PM
> To: "nanog at nanog.org" <nanog at nanog.org>
> Subject: Re: Best practice for BGP session/ full routes for customer
> 
>> On Monday, July 07, 2014 08:33:12 PM Anurag Bhatia wrote:
>>
>>> In this scenario what is best practice for giving full
>>> table to downstream?
>>
>> In our case, we have three types of edge routers; Juniper
>> MX480 + Cisco ASR1006, and the Cisco ME3600X.
>>
>> For the MX480 and ASR1006 have no problems supporting a full
>> table. So customers peer natively.
>>
>> The ME3600X is a small switch, that supports only up to
>> 24,000 IPv4 and 5,000 IPv6 FIB entries. However, Cisco have
>> a feature called BGP Selective Download:
>>
>> 	http://tinyurl.com/nodnmct
>>
>> Using BGP-SD, we can send a full BGP table from our route
>> reflectors to our ME3600X switches, without worrying about
>> them entering the FIB, i.e., they are held only in memory.
>> The beauty - you can advertise these routes to customers
>> natively, without clunky eBGP Multi-Hop sessions running
>> rampant.
>>
>> Of course, with BGP-SD, you still need a 0/0 + ::/0 route in
>> the FIB for traffic to flow from your customers upstream,
>> but that is fine as it's only two entries :-).
>>
>> If your system supports a BGP-SD-type implementation, I'd
>> recommend it, provided you have sufficient control plane
>> memory.
>>
>> Cheers,
>>
>> Mark.
> 
> 



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