L2VPN Interworking mode : IP or Ethernet

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Dec 16th, 2007
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I've read some books about MPLS L2VPN. But I got some confusion about the conception of L2VPN interworking mode: IP and Ethernet.

As I know, the differences between the two mode is the payload of the packets which transport in the PW. When we use the Ethernet mode, the payload is a ethernet frame and when we use the IP mode , the payload is a IP packet.

And I want to know that, If one side of Attach Circuit is ATM , another side of AC is ethernet. Can we use both of the 2 mode to establish a PW?

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gauravprakash Mon, 12/17/2007 - 04:52
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yes, this is ATOM, any thing over ATM. You can have two different Layer 2 encapsulation speaking at two ends, and then ATOM help you to internetwork them with Layer3 packet which is understood by them. You configure 'internetwking ip' if u hv two diferent L2 encap at two legs of VC.



showtime1984 Mon, 12/17/2007 - 05:03
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There is a scenario:


PE1 and PE2 are 7609, CE1 and CE2 are 7200 with NPE-400.When I use IP mode interworking, It's not work. When I use the Ethernet mode and config the IRB on the CE2, it works, I want to know why .

gauravprakash Mon, 12/17/2007 - 06:10
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Can u paste the config of two interfaces onPE routers which interface with CE.



showtime1984 Mon, 12/17/2007 - 06:18
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pseu-class MPLS-IP

en mpls

inter ip

Interface Gi 0/1.10

desc To_CE1

enca dot1q 10

xconnect 100 pw-class MPLS-IP


Interface atm 2/1/0.100 point-to-point

pvc 0/100 l2tran

en aal5snap

xconnect 100 pw-class MPLS-IP


interface gi 0/1.10

en dot1q 10

ip add


interface atm 1/0.100 point-to-point

ip address

pvc 0/100

en aal5snap is PE1's ldp router-id is PE2's ldp router-id

gauravprakash Mon, 12/17/2007 - 07:30
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1. Chk if LDP is ok.

2. show mpls l2trans vc de should show you if the 'MPLS VC labels has been exchanged' & 'mtu of both the sides' mtu shud be same. If this does not work.

Ur config looks ok.

showtime1984 Mon, 12/17/2007 - 07:35
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I'm sure LDP is OK.

I set the ATM MTU to 1500 bytes at the PE2,and the show mpls l2trans vc de show that the vc status UP, and the label stack is OK. But I can not ping from CE1 to CE2


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