EoMPLS using PW type 4 and 5 -- how to see the difference on the router

prima.ramadhan · ‎01-17-2013

Hi All,

I understand that there are two types of EoMPLS, VLAN based (VC type 4) and port based (VC type 5). However, I am a little confused on the configuration and the show command output on the router.

First Test

I tried to configure port based EoMPLS using below configuration between the PEs:

int gig0/1

service instance 10 eth

encap dot1q 10

rewrite ingress tag pop 1 sym

xconnect PE2 10 encap mpls

the output of show mpls l2transport vc 10 det is below:

PE#sh mpls l2transport vc

Local intf Local circuit Dest address VC ID Status

------------- -------------------------- --------------- ---------- ----------

Gi0/1 Eth VLAN 10 10.1.0.15 10 UP

however, when I did the debug mpls l2transport signaling message, the output is like this:

11774507: Jan 18 13:50:35.068 WIB: AToM LDP [10.1.0.15]: Sending label mapping msg

11774508: Jan 18 13:50:35.068 WIB: AToM LDP [10.1.0.15]: Sending label mapping msg vc type 5, cbit 1, vc id 10, group id 0, vc label 73, status 0x00000007/0x00000001, mtu 1500, vc handle 0xCD00000C

PE#sh mpls l2transport binding

Destination Address: 10.1.0.15, VC ID: 10

Local Label: 73

Cbit: 1, VC Type: Ethernet, GroupID: 0

MTU: 1500, Interface Desc: n/a

VCCV: CC Type: RA [2]

CV Type: LSPV [2]

Remote Label: 39

Cbit: 1, VC Type: Ethernet, GroupID: 0

MTU: 1500, Interface Desc: n/a

VCCV: CC Type: RA [2]

CV Type: LSPV [2]

I think above output is correct because based on Cisco live BRKOPT-2201, when doing xconnect under 2 service instances, then the routers will negotiate using pw type 5 (port based).

Second Test

However, I tried to do some investigation by using subinterface (using IoU), the configuration is like this:

PE1#

int eth0/0.1

xconnect 150.1.3.3 1 encap mpls

PE2#

int eth0/0.1

xconnect 150.1.1.1 1 encap mpls

PE1#sh mpls l2transport vc

Local intf Local circuit Dest address VC ID Status

------------- -------------------------- --------------- ---------- ----------

Et0/0.1 Eth VLAN 1 150.1.3.3 1 UP

Rack1R1(config-if)#

*Jan 18 14:09:04.511: AToM LDP [150.1.3.3]: Sending label mapping msg

*Jan 18 14:09:04.511: AToM LDP [150.1.3.3]: Sending label mapping msg vc type 5, cbit 1, vc id 1, group id 0, vc label 19, status 0x00000007/0x00000020, mtu 1500, vc handle 0xA0000001

*Jan 18 14:09:04.511: AToM LDP [150.1.3.3]: Sending notif msg

*Jan 18 14:09:04.511: AToM LDP [150.1.3.3]: Sending notif msg vc type 5, cbit 1, vc id 1, group id 0, vc label 19, status 0x00000007/0x00000001, mtu 1500, vc handle 0xA0000001

*Jan 18 14:09:04.551: AToM LDP [150.1.3.3]: Received notif msg, id 14

Rack1R1(config-if)#

*Jan 18 14:09:04.551: AToM LDP [150.1.3.3]: Received notif msg, id 14 vc type 5, cbit 1, vc id 1, group id 0, vc label 0, status 0x00000007/0x00000001, mtu 0, vc handle 0xA0000001

Rack1R1#sh mpls l2transport binding

Destination Address: 150.1.3.3, VC ID: 1

Local Label: 19

Cbit: 1, VC Type: Ethernet, GroupID: 0

MTU: 1500, Interface Desc: n/a

VCCV: CC Type: CW [1], RA [2]

CV Type: LSPV [2]

Remote Label: 17

Cbit: 1, VC Type: Ethernet, GroupID: 0

MTU: 1500, Interface Desc: n/a

VCCV: CC Type: CW [1], RA [2]

CV Type: LSPV [2]

I have two questions based on above result:

1. In the second test, why they negotiate to use vc type 5? based on few literatures, when using subinterface for xconnect, the router is supposed to negotiate the vc to use PW type 4 (VLAN based) right?

2. Why on first test, the local circuit (show mpls l2transport vc) shows that it is an "Eth VLAN"? I thought it means that the PW type is 4, which is VLAN based? Please correct me if I am wrong.

Local intf Local circuit Dest address VC ID Status

------------- -------------------------- --------------- ---------- ----------

Gi0/1 Eth VLAN 10 10.1.0.15 10 UP

3. How can we correctly see which PW type is used in the EoMPLS? which command to use?

Thanks.

skanuri · ‎02-01-2013

Hi...

sh mpls l2transport binding--> is the command to check for the VC type negotiated.

If it shows "ethernet" that means it is VC Type 5. And if it shows "Vlan" that means it is VC Type 4.

BTW, the negotiation does not depend on the attachment circuit type rather it's the PW property.

Thanks

Sai

rsimoni · ‎02-01-2013

Hi Prima,

I am attaching the answer I gave some time ago to a similar thread:

"

you are referring to EoMPLS Pseudowire Types (which are better defined in rfc4446 and not 4448) and indeed there are 2 ways to handle tags.

VC Type 4 : The original 802.1Q tag is inserted in the EoMPLS payload (along with the MPLS label) before forwarding it to the MPLS core. At the ingress of the remote end or receiving PE the 802.1Q tag is stripped off before its transmission to the internal bus. If a packet is received from the MPLS core without a tag (ether type of the packet is other than 0x8100) the packet is dropped.

VC Type 5 : In EoMPLS VLAN mode configuration, only the MPLS label is added to the packet transmitted to the MPLS core. On the ingress of the remote end or receiving PE the MPLS label stack is popped out before the transmission on the internal bus. If Port mode is configured instead, the 802.1Q tag is also carried along with the MPLS label

The actions taken by the PE interfaces facing the CE are solely determined by the specific interface configuration. If such configuration requires 802.1Q tagging, the egress frame is tagged; otherwise the egress frame is sent untagged. EoMPLS VC type 5 is the default configuration mode on the platforms supporting it. Meaning that the PEs will try to first negotiate and use VC 5, if one of them (or both) does not support it they will reverse to VC 4. EoMPLS type VLAN offers backward compatibility in case the remote peer does not support VC type Ethernet.

VC type 4 or VC type 5 is not a configurable option and is platform dependent, the capability is instead auto

sensed at control plane level"

Riccardo