The MPLS-OPS Archive

["wanglei" <wanglei@harbournetworks.com>]

----- Original Message ----- 
From: "Aries C" <cariesc@hotmail.com>
To: <mpls-ops@mplsrc.com>
Sent: Sunday, February 16, 2003 7:53 PM
Subject: Re: [MPLS-OPS]: Route Distinguisher Questions


> 
> >From: "john smith" <johnsmith0302@hotmail.com>
> >To: wanglei@harbournetworks.com, cariesc@hotmail.com, mpls-ops@mplsrc.com
> >Subject: Re: [MPLS-OPS]: Route Distinguisher Questions
> >Date: Sun, 16 Feb 2003 11:18:05 +0000
> >
> >>From: "wanglei" <wanglei@harbournetworks.com>
> >>To: "Aries C" <cariesc@hotmail.com>, <mpls-ops@mplsrc.com>
> >>Subject: Re: [MPLS-OPS]: Route Distinguisher Questions
> >>Date: Sun, 16 Feb 2003 17:58:20 +0800
> >>
> >>    RD is the identifier of a vrf,it must be unique in a PE,
> >>so in PE ,when a route comes,the PE can find which vrf it
> >>belongs to.
> >>    Route Target is mainly used for controlling the route table
> >>import and export policy.
> >>    Don't mix the two.
> >>in my opinion:
> >>1¡¢ RD is the identifier of VRF, it must be unique in one PE.
> >>it can be different even in the same VPN but not in the same PE.
> >>but in order to reduce the memory requirements ,each vrf in the
> >>same VPN can use the same RD.
> >>the core is that RD is the identifer to identify different vrfs
> >>in one PE.
> >>
> >
> >why would i want to use 2 RDs in the same VPN? can you give me a specific 
> >example?
> >
> 
> That's a good question. Again, the book mentioned :
> 
> "However, if this site at some point in the future will become a
> member of an extranet VPN, do not take this approach because it might incur
> config. issues when trying to provision the extranet VPN.
> 
> For example, suppose a different RD is used for each VPN. If a particular
> site wants to be a member of multiple VPNs, it's not possible to to identify
> which route distinguisher to use for the site because it belongs to more
> than one VPN."
> 
> But I could not digest, where the issue would be, as I have different RD for 
> different VPN anyway. Why I can not route site A of VPN-A (RD 100:27) and 
> site B of VPN-B (RD 100:26) ?? What's the issue ?
________________________________________________________________________________________
Perhaps i don't understand your question very well,but if you only want to let 
the route be transfered between VPN-A and VPN-B,it is nothing with RD
you can do like this:

PE2 (config)#ip vrf VPN-A
PE2 (config-vrf)#rd 100:27
PE2 (config-vrf)#route-target 2:2
PE2 (config-vrf)#exit

PE3 (config)#ip vrf vpn2
PE3 (config-vrf)#rd 100:26
PE3 (config-vrf)#route-target 2:2
PE3 (config-vrf)#exit

so ,you see when route study among different VPNs(or we can say VRFs),it only needs 
the same route target.
if you want to control route study more subtly,you can use the "import" and "export" option
 



















> 
> The problem with assigning unique RD per VRF (even in the same VPN) is 
> operation issue, and perhaps scalability.
> 
> 
> TIA
> 
> Aries C.
> 
> 
> 
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