The MPLS-OPS Archive

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

   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.   

2¡¢just as the first answer,if you comprehend it.

3¡¢just as the first answer,if you comprehend it.

4¡¢don't mix RD and Route Target
 





----- Original Message ----- 
From: "Aries C" <cariesc@hotmail.com>
To: <mpls-ops@mplsrc.com>
Sent: Sunday, February 16, 2003 4:58 PM
Subject: [MPLS-OPS]: Route Distinguisher Questions


> Hi All,
> 
> I m reading a book of Ivan Pepelnjak's book (MPLS and VPN Arch.)
> At page 191 Chapter 10, there's 3 paragraph get me confused :
> 
> 
> "Each VRF within the PE router configuration needs to have an associated RD, 
> which might or might not be related to a particular site or VPN membership 
> of that site. In the most common case, where a site belongs only to one 
> intranet VPN, it's technically possible and recommended, to use unique RD 
> for the VPN. However, if this site at some point in the future will become a 
> member of an extraner 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.
> 
> Therefore, for network topologies other than simple intranet model, use the 
> same route distinguisher per VRF, rather than per VPN, to avoid this type of 
> conflicting config. and to reduce the memory requirements of the PE router. 
> In the case of an extranet VPN, this means the VRF that makes up the VPN 
> uses the same RD regardless of the particular VPN site to which the VRF 
> belongs. "
> 
> 
> The question are :
> 
> 1. is definition RD per VRF : all RDs are unique regardless which VPN it 
> belongs to ?
> 2. Is definition RD per VPN : one RD is used acrossed all VRF belongs to a 
> VPN ?
> 3. Why the paragraph mentions RD per VRF is more recommended ( because 
> configuration conflict and reduce the memory requirements), as compared to 
> RD per VPN ?
> 4. Can I use RD per VPN, though a site could belong to multiple VPN. Because 
> theoritically, we can use Route Target to control export and import (again 
> the uniqueness is taken care with RD, and also different VPN has different 
> RD anyway i.e. VPN A = RD 100:27 and VPN B = 101:27).
> 
> 
> Could anyone educate me on this.
> 
> 
> TIA
> 
> Aries C.
> 
> 
> 
> 
> 
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