Any Transport Over MPLS (AToM)

This topic is to discuss the following lesson:

Thank you, Rene, for what you do. I like very much the way you simplify complicated things. Keep doing great stuff !!!


Rene! its a great walkthrough tutorial but little help required. which ios version to use? 12.4 does not support “xconnect 13 encapsulation mpls” command. waiting for your reply

Hi Babar,

I think the problem is not the 12.4 IOS version but the platform you are using. I’m not 100% sure but I believe in GNS3 you can only do it on the 7200 router, not the 3600/3700 series. I haven’t checked it on my 1841 and 2811 routers but I can take a look if you want.


Thanks Rene,
I have changed the ios to 12.4.9T with the platform 7200. Still its not working…
Any ideas??

I just tried one of the 3725 images:

(C3725-ADVENTERPRISEK9-M), Version 12.4(15)T7

R1(config)#interface fastEthernet 0/1
R1(config-if)#xconnect ?
  A.B.C.D  IP address of peer

That should do the job.

Hi Rene,

Thanks for all the tutorials you post. They are really good.

One question regarding AToM: if I wanted to carry a dot1q trunk between HQ and PE1 would that change the configuration on PE1?

Thanks again,


Hi Jose,

Thanks, glad that you like it!

I’m not sure if you have to make any changes…I would have to test it. You can quickly try it by making a sub-interface on the HQ and Branch router that tags the outgoing traffic, see if they can still reach each other.


Hi Rene,

It’s a very nice tutorial. BTY, can you publish something for mpls vpls and hvpls services ?

Thank you


Hi Taslim,

For sure, I’ll put this on my “to write” list.


hi Rene
why i can’t use XConnect command in the interface?
what happlen?

 interface ethernet 0/0
 xconnect 13 encapsulation mpls 
Incompatible with ip address command on Et0/0 - command rejected.



Hi Bounpasong,

You can’t have an IP address on the interface that you want to use xconnect on. Remove the IP address and it will work.


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hi Rene
thank you very much, I like your post very much @_@


Hi Rene !

Excellent lesson !

Could you please do a lesson about VPLS, VPWS and the diferrence between them and between MPLS L2VPN ?



great example but I do have a question for you . can we call this also L2TPv3 or EoMPLS as well ?I really get confused between those descriptions .Can you please explain it to me if there are any differences ?


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Hi Georgi,
These terms all start to run together don’t they?

First, let’s talk about AToM vs EoMPLS. EoMPLS is AToM that is transporting a specific protocol (Ethernet). AToM is capable of transporting other layer 2 protocols as well, so it has a more broad meaning. The confusion is that most people use Ethernet at layer 2, so in that case EoMPLS and AToM appears to be the same thing. Think of it this way: EoMPLS is a specific kind of AToM just like a Poodle is a specific kind of Dog.

Now let’s talk about L2TPv3 vs EoMPLS. These are both trying to accomplish the same thing: Extend a layer 2 boundary across a WAN, but they use different protocols to do it. Each has their own pro’s and con’s. Here are a few highlights:

Wide hardware support
Better traffic engineering control

Requires end-to-end MPLS configuration, which is usually more expensive to the customer

Any IP based Internet connection is supported (DSL, Cable Modem, etc)
Less expensive than MPLS

Newer technology, so not as widely supported as EoMPLS


Hello Rene,

I have the same message as Bounpasong:

PE1(config-if)#xconnect 13 encapsulation mpls
Incompatible with ip address command on Fa2/0 - command rejected.

I am okay to remove the IP address but OSPF and MPLS will go down…

How did you manage this situation ?

Thanks a lot,
Kind regards,

Hi Rene / Andrew
Another awesome job / lesson
I re-created the scenario, but I can see we will have an MTU problem- I understand the obvious next step would be to increase it on MPLS enabled interfaces because of additional overhead ?
What would be recommended size of MTU on them ? 1526 bytes?
Thank you

I believe ip mtu 1456 would do the trick, and here’s why:

1500 (default) - 20 (TCP Header) - 20 (IP Header) - 4 (MPLS Label) = 1456

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