[c-nsp] Anycast//DNS - BGP

[Robert Raszuk]

Hi Adam,

> Hi Henry,
>
> Please note that even though the diverse-path RR feature is easy to deploy
> there's one possible drawback to be taken into consideration
> Once configured with the diverse-path feature the RR will start to advertise
> all paths for all prefixes to all its clients

Completely wrong. You are mixing diverse-path with add-paths - two 
completely different features.

With diverse path you are sending _only_ second best on the session 
dedicated for the second best. The benefit is that you are controlling 
very well number of paths on your clients, do not need to upgrade the 
clients yet can benefit from BGP level load balancing as well as PIC.

> -so you should make sure all
> the RR clients can cope with the tables growth (depending on the # of
> prefixes and the # of alternate paths per each prefix) -please note that
> this will affect all the bgp speakers not just those clients that really
> need the diverse paths for loadsharing or anycasting purposes

Even with add-paths you are really talking about the number of paths 
which need to be advertised can be chosen by cli.

> If you are using mpls in your backbone you'd definitely want to be using
> different RD per each bgp speaker to make the prefix unique from RR's
> perspective

RD per VRF is a good recommendation. But this falls into your issue of 
having all paths on each PE where non null RT intersection exists.

Best,
R.


> Matthias,
> What I've used for anycast or multipath in pure IP bgp-RR environments prior
> to the diverse-path or add-path features was adding the Path-Based-RR to the
> existing AddressBased-RR or Topology-Bassed-RR
> So for 6 paths you'd have 6 RRs each choosing the same prefix with different
> path as best passing it down to all clients -and have clients to peer with
> all 6 RRs
> Please note these where pure control plane RRs
> As you can see this doesn't scale well as the separate RR infrastructure
> needs to be built for each diverse path that needs to be propagated to RR
> clients
>
>
> adam
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Robert Raszuk
> Sent: Friday, May 04, 2012 5:48 PM
> To: henrry huaman
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Anycast//DNS - BGP
>
> Hi Henry,
>
>   >  Currently we have issues with the RR (Only select the main route)
>
> That's an easy one to solve :)
>
> Try using either add-paths or diverse-path on the RR. The latter is much
> easier as it does not require upgrade of all of your BGP speakers !
>
> http://goo.gl/KDjlg
>
> Best,
> R.
>
>> We want to work with DNS that are span geographical. Our DNS have the same
> IP.
>> We need to configure the Backbone IP (BGP) to distribute this IP
> (Anycast).
>> Could you have any examples over how to deployment Anycast?
>> Currently we have issues with the RR (Only select the main route)
>>
>> Thanks a lot!
>>
>> Henry
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