The MPLS-OPS Archive

[Roger Clark Williams <rogerw@nordlink.com>]

Jan, a basic misunderstanding here: Between a CE and PE there is a
standard IP connection. No vrf anything. The VRF is on the PE only Think
about it this way: The PE might have a number of separate connections and
needs to keep those connections apart. All the routes can't go into a
single routing table as then the various CEs would have routes to each
other. No VPN is that scenario. To keep the CEs apart you need separate
routing tables, tables that keep the routing for each group apart form
all the others. These are the VRFs. The PE acts as though there is a
completely separate router looking at each CE.

Also, the CE (Customer Edge) is not considered an MPLS router, just a
simple IP router, because it is not running MPLS. The 72xx you mention is
indeed the Provider Edge (PE, the "edge" of the provider's
network that interfaces with the edge of the customer's network). Because
it is running MPLS the PE is considered an MPLS PE. Assuming the core of
the Provider's network is running MPLS, the core routers you mentioned
would be MPLS P routers. 

However, keep in mind that the core doesn't need to be running MPLS. MPLS
is (arguably) a form of Layer 3 encapsulation and can use any Layer 2
transport system as though it were an open pipe. So, MPLS PE routers can
look "through" an ATM pipe with the ATM core switches knowing
nothing about MPLS.

So, short statement:
CEs are not MPLS, just regular IP
PEs are MPLS, talking IP to the CE and MPLS between themselves
P routers can be MPLS but don't have to be.

I hope this helps a bit.

Roger Williams

Resent-Date: Thu, 19 Dec 2002 02:24:37 -0500
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Date: Thu, 19 Dec 2002 07:56:14 +0100
From: Jan Czmok <jan.czmok@gatel.net>
To: mpls-ops@mplsrc.com
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Subject: [MPLS-OPS]: the "right" configuration
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Dear Collegues,

just a quick question after reading all the specs and docs.
Imaging the following scenario:

        - Cisco 2610 Router at Customer (so it's MPLS-CE ?)
        - Cisco 72xx Router at each POP (so it's MPLS-PE?)
        - Juniper Mxx+Cisco Router at Core (so it's MPLS-P ?)

        Am i right with the namings ?

So to get a working vpn i have to:

        - "ip vrf"ing the interfaces at MPLS-CE towards PE
        - "ip vrf"ing the interface at MPLS-PE towards MPLS-CE
        - run iMBGP at a second instance between the involved PE's
        
        Right ? Or missing something here ?
        

Some questions:

        - what decent routing protocol need to be used between PE/CE ?
        - isis is run in core & mpls-pe vor routing exchanges and
          iBGP route-reflector for bgp routes.

        
Some working sample configurations might be handy...

--jan

--
     Jan Ahrent Czmok - Senior Network Engineer - Access Networks
Global Access Telecommunications, Inc. - Stephanstr. 3 - 60313 Frankfurt
voice: +49 69 299896-35 - fax: +49 69 299896-66 - email: czmok@gatel.de

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