RE: OT: GS Archives Search

Personally that seems overly confusing to me. Yes Route Targets are an attribute of the route, but that attribute is not part of the BGP Bestpath Selection. I'm not sure how it ties together. It's simpler to think of it this way:

It's given that customers of a Service Provider will have overlapping IP addressing in their VPNs, e.g. you will have more than two customers who use the 10.0.0.0/8 network. The RD is how you tell them apart. If you have customer "A" with RD "A" and customer "B" with RD "B" the routes "A:10.0.0.0/8" and "B:10.0.0.0/8" become unique. This is all the RD does.

The Route Target tells you which VRF table the route belongs to. You have to separate the two attributes because sometimes you want the same route to belong to multiple VRF tables. This is common in what's known as "Central Services VPNs". For example if the Service Provider hosts email for customers, that route to the mail server would have to be in the routing table of multiple customers. This doesn't break the rule of the route having to be unique though, which is what the RD does.

Like I said you may be able to find more clarification in this video: http://goo.gl/Y0imB.

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com

Internetwork Expert, Inc.
http://www.INE.com

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Marko Milivojevic
Sent: Monday, March 26, 2012 6:00 PM
To: Yemi Salau
Cc: ccielab_at_groupstudy.com
Subject: Re: OT: GS Archives Search

Simple reason - prefixes are passed on through the bestpath selection process where the best one is chosen based on attributes. RT is a community, which is an attribute. This means that given two prefixes with different RTs would be treated as equals when it comes to bestpath selection. With RD we extend the prefix space to 86 bits and then use those for comparison instead of 32bit ones.

[ iPhone, brevity, etc disclaimer :-) ]

--
Marko Milivojevic - CCIE #18427
:: This message was sent from a mobile device. I apologize for errors and brevity. ::
On Mar 26, 2012, at 14:44, Yemi Salau <salauolayemi_at_yahoo.co.uk> wrote:
> Thanks Marko, reading RFC 4364, I was trying to figure out why RT 
> couldn't
do the same job of RD for uniquely separating VPN-IPv4 routes within the provider MPLS cloud. I'll watch your video when I get home. Many Thanks.
>
> From: Marko Milivojevic <markom_at_ipexpert.com>
> To: Yemi Salau <salauolayemi_at_yahoo.co.uk>
> Cc: ccielab_at_groupstudy.com
> Sent: Monday, 26 March 2012, 16:25
> Subject: Re: OT: GS Archives Search
>
>
> Yemi,
>
> I'm not sure about the Archive search, but I can certainly help you 
> with RD
and RT. Almost two years ago I hosted a free online training session called "MPLS 101". You can find it, together with all other recorded vLectures on many other subjects here:
>
> http://bit.ly/vLecture
>
> Please go ahead and watch it and if you have any questions feel free 
> to ask
them here.
>
> --
> Marko Milivojevic - CCIE #18427 (SP R&S) Senior CCIE Instructor - 
> IPexpert
>
> On Mon, Mar 26, 2012 at 10:18, Yemi Salau <salauolayemi_at_yahoo.co.uk> wrote:
> Guys,
>
> I remember a time where I was able to search the GS archives for 
> stuffs. Is
this still available today? I want to search out some stuffs on RD vs RT.
>
> Yemi
>
>
> Blogs and organic groups at http://www.ccie.net
>
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