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L2 MPLS Tunnel Solution

I want to setup a L2 MPLS Tunnel accross our Layer 3 IP transit core network. Anybody has the useful link or infomation for this.

2 REPLIES

Re: L2 MPLS Tunnel Solution

Hi,

Unfortunately I cannot open your Visio file. So just a thought: if your core network is IP, why not to use L2TPv3? It does not require any changes in the core and will deliver the same functionality as Ethernet over MPLS and the like.

For configuration examples have a look at "MPLS AToM: Configuring"

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00804a0d1b.html

and at "L2TPv3: Layer 2 Tunneling Protocol Version 3"

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00804420e7.html

Hope this helps! Please rate all posts.

Regards, Martin

Re: L2 MPLS Tunnel Solution

To implement a PW or L2MPLS Transport you need to implement 3 encapsulations.

1) PSN Tunnel - This is to get PDU from ingress to egress PE.

You can use MPLS label, GRE tunnel, L2TP tunnel.

Cisco implements this in MPLS Label.

2) Demultiplexer field - This is used to identify individual circuits within a tunnel.

Could be an MPLS label or GRE key. Cisco uses MPLS Label.

3) Emulated VC encapsulation - This gives information on enclosed Layer-2 PDU.

This is implemented as a 32-bit control word.

Now since you have a IP Core Network. You can proceed as below.

1) Implement you PSN Tunnel in MPLS Over GRE. We cannot make this pure GRE as the Demux field as a GRE key is not the supported option in Cisco.

2) Run Directed LDP over this tunnel between the two Edge PE and exchange the Demux Field.

This Demux Field is nothing but your VC Label which is generated by mapping of VCID and

Interface.

3) COntrol Word is negotiated based on the Emulated VC media type.

So you have two options to go,

a) Implement MPLS Over GRE with Directed LDP (There isnt a specific document for this)

b) Implement L2 Pseudowire with L2TPV3.

(The link for L2TPv3 has is the same given by Martin)

This is how you can implement L2MPLS over a IP Core. Since pure GRE PSN method isnt implemented in Cisco although it is there in specifed in the RFC.

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