RE: OT: GS Archives Search

Don't worry m8, you learn something new every day.

From: Narbik Kocharians [mailto:narbikk_at_gmail.com]
Sent: Tuesday, March 27, 2012 10:43 AM
To: Brian McGahan
Cc: Marko Milivojevic; Yemi Salau; ccielab_at_groupstudy.com
Subject: Re: OT: GS Archives Search

hahahahahaha

I thought it all happens automagically.

On Tue, Mar 27, 2012 at 8:34 AM, Brian McGahan
<bmcgahan_at_ine.com<mailto:bmcgahan_at_ine.com>> wrote:
> The "Route-target" is a BGP extended community that indicates which routes
should be exported from a given VRF or imported into a given VRF.
The Route Target doesn't control which routes leave the VRF to go into VPNv4
BGP, redistribution controls this. If you don't set a Route Target the VPNv4
routes will still originated, but no one will be able to import them on the
other side. This is actually a common misconfiguration for MPLS L3VPN.

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

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

From: Narbik Kocharians [mailto:narbikk_at_gmail.com<mailto:narbikk_at_gmail.com>]
Sent: Monday, March 26, 2012 9:18 PM
To: Brian McGahan
Cc: Marko Milivojevic; Yemi Salau;
ccielab_at_groupstudy.com<mailto:ccielab_at_groupstudy.com>
Subject: Re: OT: GS Archives Search
Since we all know what VRFs are. Remember that the VRF is NOT operational
without an RD.
What is an RD? An RD is a 64 bit value that is attached to the customer's IPv4
address, to make it a Unique 96 bit address called VPNv4. These addresses are
ONLY exchanged between the PE routers. In Brian's example, RDs distinguish one
route from another, in his example 10.0.0.0:A from 10.0.0.0:B.

I think that the name "VPNv4" is the worst name they could assign to these
addresses, because many people think that RDs define the VPN, and they DO NOT
define the VPN.

Once the PE router attaches the RD to the CE routes, it then sends the VPNv4
address/es to the other PE router/s. The receiving PE router strips the RD
from the VPNv4 prefix, and it's left with an IPv4 address.

NOW..How does the receiving PE know which VRF does the IP address belong to?
The answer is "Route-Target".

The "Route-target" is a BGP extended community that indicates which routes
should be exported from a given VRF or imported into a given VRF.
I hope this helped.
On Mon, Mar 26, 2012 at 6:27 PM, Brian McGahan
<bmcgahan_at_ine.com<mailto:bmcgahan_at_ine.com>> wrote:
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<http://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<http://10.0.0.0/8>" and "B:10.0.0.0/8<http://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<mailto:bmcgahan_at_INE.com>

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

-----Original Message-----
From: nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>
[mailto: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<mailto: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<mailto: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<mailto:markom_at_ipexpert.com>>
> To: Yemi Salau <salauolayemi_at_yahoo.co.uk<mailto:salauolayemi_at_yahoo.co.uk>>
> Cc: ccielab_at_groupstudy.com<mailto: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<mailto: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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