Cisco is known for the inconsistencies between platforms and different IOS versions. I came across another that was rather annoying. Now between linecards.
Trying to configuring the following standard sub-interface Ethernet AToM tunnel on a Cisco 7606 with a ES+ linecard:
pseudowire-class CISCO encapsulation mpls ! interface Te2/2.2 encapsulation dot1Q 2 no ip redirects no ip directed-broadcast no ip proxy-arp xconnect 10.5.0.99 12345 encap mpls pw-class CISCO
Yields the following misleading error…
7606(config)#int te2/2.2 7606(config-subif)# xconnect 10.5.0.99 12345 encap mpls pw-class CISCO MPLS encap is not supported on this circuit
This is enough to annoy you for some time. If you have a look at the supported capability on CLI or using Cisco Feature Navigator you will see the AToM is indeed supported.
7606#sh mpls l2transport hw-capability interface te2/2 | section Eth VLAN Transport type Eth VLAN Core functionality: MPLS label disposition supported Distributed processing supported Control word processing supported Sequence number processing not supported VCCV CC Type CW  processing not supported Edge functionality: MPLS label imposition supported Distributed processing supported Control word processing supported Sequence number processing not supported Fast backup switchover is supported Standby RP forwarding is not supported
The next step would generally be to consult the DOC-CD to confirm you didn’t messed up the really simple config. But this only adds to the head scratching.
Cisco Feature Navigator says AToM is supported, the DOC-CD shows the correct config used, CLI says it is supported, so what gives.
Cisco’s dumb sense of humor.
The ES+ Linecard has its own way of taking certain commands, which includes AToM.
On the 7600 ES+ linecard the configuration happens below a instance instead of a sub-interface configuration:
interface TenGigabitEthernet2/2 no ip address no ip redirects no ip proxy-arp service instance 2 ethernet description atom on a ES_plus encapsulation dot1q 2 xconnect 10.5.0.99 12345 encap mpls pw-class CISCO
For more information read this link at Cisco.
Trust that was helpful :)