There are two things that we have to do to enable E-OAM: configure oam profile that will define way OAM will work and attach that profile to physical interface. OAM’s are not working on subinterfaces. In action section you define what action will router take when particular error occurs, in this example interface will be put in err-disable state.

Let’s look at the configuration

ethernet oam profile EOAM_6
 mib-retrieval
 remote-loopback
 action
  critical-event error-disable-interface
  dying-gasp error-disable-interface
  link-fault error-disable-interface
  session-down error-disable-interface
!
interface GigabitEthernet0/2/0/25
 description Local E-LAN, L2 Multicast
 speed 100
 ethernet oam
  profile EOAM_6
  remote-loopback

Of course both sides have to support OAM and have it configured. To check OAM status on particular port you have to issue show ethernet oam discovery interface command. It will show information and status of OAM neighbor.

RP/0/RSP0/CPU0:PE6#show ethernet oam discovery interface gigabitEthernet 0/2/0/25 
GigabitEthernet0/2/0/25:
Local client
------------
  Administrative configuration:
    PDU revision:                        12
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                Y
    Maximum PDU size:                  1500
    Mis-wiring detection key:          2B54

Operational status:
    Port status:                Operational
    Loopback status:                   None
    Interface mis-wired:                  N

Remote client
-------------
  MAC address:               0027.0cf2.f414
  Vendor (OUI):                    00.00.0C (Cisco)

  Administrative configuration:
    PDU revision:                         2
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                N
    Maximum PDU size:                  1500

In following example we see that connection to remote device is Operational and it support putting interface on loopback as well as MIB retrieval. So, let’s put interface on remote side on loopback.

RP/0/RSP0/CPU0:PE6#ethernet oam loopback enable gigabitEthernet 0/2/0/25
GigabitEthernet0/2/0/25 entered loopback mode successfully.

And now verify the state

RP/0/RSP0/CPU0:PE6#show ethernet oam discovery interface gigabitEthernet 0/2/0/25 
GigabitEthernet0/2/0/25:
Local client
------------
  Administrative configuration:
    PDU revision:                        11
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                Y
    Maximum PDU size:                  1500
    Mis-wiring detection key:          2B54

Operational status:
    Port status:                Operational
    Loopback status:                 Remote
    Interface mis-wired:                  N

Remote client
-------------
  MAC address:               0027.0cf2.f414
  Vendor (OUI):                    00.00.0C (Cisco)

  Administrative configuration:
    PDU revision:                         1
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                N
    Maximum PDU size:                  1500

As you can see Loopback status is set to Remote which indicates that remote side has set loopback on interface. In this state all data except of OAM BPDU’s are sent back to sender. On some platforms you can fetch additional extended information from remote side, but if it don’t following warning message will be displayed.

RP/0/RSP0/CPU0:PE6#show ethernet oam discovery interface gigabitEthernet 0/2/0/25 remote 
Failed to get item 'GigabitEthernet0_2_0_25/get_remote_discovery_info' from SysDB: 'Ethernet Link OAM' detected the 'warning' condition 'The remote peer does not support the required feature'

At the end we remove loopback on remote side and verify that link is operational again.

RP/0/RSP0/CPU0:PE6#ethernet oam loopback disable gigabitEthernet 0/2/0/25                
GigabitEthernet0/2/0/25 left loopback mode successfully.
RP/0/RSP0/CPU0:PE6#show ethernet oam discovery interface gigabitEthernet 0/2/0/25 
GigabitEthernet0/2/0/25:
Local client
------------
  Administrative configuration:
    PDU revision:                        12
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                Y
    Maximum PDU size:                  1500
    Mis-wiring detection key:          2B54

Operational status:
    Port status:                Operational
    Loopback status:                   None
    Interface mis-wired:                  N

Remote client
-------------
  MAC address:               0027.0cf2.f414
  Vendor (OUI):                    00.00.0C (Cisco)

  Administrative configuration:
    PDU revision:                         2
    Mode:                            Active
    Unidirectional support:               N
    Link monitor support:                 Y
    Remote loopback support:              Y
    MIB retrieval support:                N
    Maximum PDU size:                  1500