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Ethernet CFMEthernet CFM
Ethernet Connectivity Fault Management (CFM, IEEE 802.1ag) is an end-to-end Ethernet OAM that can cross multiple domains to monitor the health of the entire service instance. A service instance can be a native Ethernet VLAN, an EoMPLS (aka E-Pipe) or a VPLS instance. End-to-end can be PE to PE, or CE to CE. CFM is a connectivity checking mechanism that uses its own Ethernet frames (its Ethertype is 0x8902 and it has its own MAC address) to validate the health of the service instance. 
CFM Terminology

Maintenance Domain (MD)
In Ethernet CFM, an MD is a management space for monitoring and administering of a network. An MD is owned by a Maintenance Entity (ME). Figure 1 shows different MDs, each owned by a single entity. 
A unique maintenance level from 0 to 7 is assigned to each domain. The larger the domain, the higher the value. For instance, the customer domain in figure 1 would be assigned the highest value, 7, while the operator domain would be assigned the lowest value, 0. The MDs are defined to have hierarchical relationships with other domains. Domains cannot intersect, however, they can be touching &/or nested.
Ethernet CFM exchanges messages and performs operations on a per-domain basis. For instance, in figure 1, CFM running at Operator 1 level does not allow discovery of the network by Provider or Customer level.
Maintenance Point
A Maintenance Point is a demarcation point for the CFM frames. It is an interface (physical port or logical interface) that participates in an MD. A maintenance point filters the CFM frames by dropping frames that do not belong in the correct MD. The maintenance points must be configured manually. There are two types of maintenance points-
Maintenance Endpoint (MEP): MEPs initiate and terminate CFM messages. MEPs define the boundary of an MD. 
Maintenance Intermediate Point (MIP): MIPs receive CFM messages and respond to originating MEPs. A MIP never initiates messages and does not expect any CFM messages. 
Maintenance Association (MA)
A set of MEPs that have the same MA identifier and MD level within one service instance to verify the integrity of the service. It is represented by the solid line in figure 2.

The following rules apply to CFM message processing-
If the MD level of the CFM message is higher than the MD level of the MEP/MIP, the MEP/MIP transparently passes the CFM message.
If the MD level of the CFM message is lower than the MD level of the MEP/MIP, the MEP/MIP discards the CFM message.
If the MD level of the CFM message is equal to the MD level of the MEP/MIP, the MEP/MIP processes the CFM message. Depending on the type of CFM message, the MEP/MIP responds to, transports to or accepts the message.
A MEP/MIP with a particular MD level generates a CFM message only at that level. In figure 2, the customer is interested in only the health of the end-to-end connection. Therefore, the MA has a high MD level (for example, MD=7). The MEPs/MIPs in provider and operator networks transparently pass customers CFM messages. The Provider is interested in the health of the service it provides. Therefore, the MA has a higher MD level (for example, MD=5) than the operators MD level but lower than the customer MD level. So, the MEPs/MIPs in operator network transparently pass the provider's CFM messages. The operators are interested only in the health of their own networks. Therefore, their MAs have lowest MD level (for example, MD=0). So, the CFM messages are confined to their own network.
CFM Messages
A CFM message has its own frame format. All CFM messages are Ethernet frame with an etherype of 0x8902. Figure 3 shows a CFM frame format.
MD Level - An MD of the CFM message from 0 to 7
CFM Version - Currently, it is set to 0
CFM OpCode - This indicates the type of CFM messages (discussed next)
CFM PDU - Each CFM message type is associated with a different CFM PDU. Each PDU contains one or more informational TLVs

All CFM messages end with an empty End TLV.
There are 5 different types of CFM messages-
1. Continuity Check Message (CCM): A MEP generates CCM messages to announce its local port and interface status. If CCM is enabled, an MA tracks CCM messages from all MEPs, and is performed at a defined interval. CCM messages always use multicast destination MAC address and has the format of 01-80-C2-00-00-3x where 'x' relates to value of MD level (0-7).
2. Loopback Message (LBM): A MEP generates a CFM LBM message when the CFM loopback test is performed. The packet is destined to the MAC address the loopback test intends to reach. On an Alcatel-Lucent device, this can be done as follows-CFM Loopback TestA:SW1# oam eth-cfm loopback 0c:a4:02:05:cc:01 mep 1 domain 3 association 3
Eth-Cfm Loopback Test Initiated: Mac-Address: 0c:a4:02:05:cc:01, out service: 35
Sent 1 packets, received 1 packets [0 out-of-order, 0 Bad Msdu]
A:SW1#

The packet capture of an LBM message is as follows-

3. Loopback Reply message (LBR): A MEP/MIP responds with LBR message when it receives an LBM destined to its own MAC address. The packet destination MAC address is the source MAC address of the LBM message. The packet capture of an LBR message is as follows-

4. Linktrace message (LTM): A MEP generates LTM message when link trace is performed. The packet is destined to multicast MAC address 01-80-C2-00-00-3y where 'y' corresponds to MD level as below:
 MD Level
 y
 7 F 
 6 E
 5 D
 4 C
 3 B
 2 A
 1 9
 0 8

On an Alcatel-Lucent device, link trace test can be performed as follows-
Link Trace testA:SW1# oam eth-cfm linktrace 0c:a4:02:05:cc:01 mep 1 domain 3 association 3
Index Ingress Mac Egress Mac Relay Action
----- -------------------- -------------------- ---------- ----------
1 00:00:00:00:00:00 0C:A4:02:05:CC:01 rlyHit terminate
----- -------------------- -------------------- ---------- ----------
No more responses received in the last 6 seconds.

The packet capture of an LTM message is as follows-

5. Linktrace Reply message (LTR): A MEP responds with an LTR message when it receives an LTM message destined to its own MAC address. The destination MAC address is the source MAC address of LTM message. The packet capture of LTR message is as follows-


Configuring CFM
Figure 4 shows a sample network with Provider and Customer MAs. Two steps are required to configure CFM in VPLS network - 1) The MD and MA need to be created first, then 2) the MEP/MIP can be created in the VPLS service instance and added to the defined MD and MA.
When defining an MD, the level of the MD must be specified. One MD can contain one or more MAs. Figure 4 illustrates an example of CFM in provider and customer domains. VPLS instance 50 is deployed in all 3 provider network's PE routers. Customer routers connect to PE routers through an attachment circuit. In this example, the customer uses the MD name Customer_Domain with level 7, and the provider uses the MD name Provider_Domain with level 3. The customer and provider have their own MAs. With this configuration, the customer's MD level is higher than the provider's MD level and hence the VPLS network will transparently pass customer CFM messages. 
When deploying MEPs in a VPLS service, the direction of flow must be specified. In VPLS, the traffic coming to a PE router from an interface connecting to the CE router is considered to be in up direction. While the traffic coming to the PE router on a Pseudowire exiting to a CE router is considered to be in down direction. 
In an Alcatel-Lucent 7x50 device, the first step to enable CFM is to create an MD. Each MD has an index, a name and an MD level. Many MAs can be defined under the same MD. After the MD is created, the MA can be created under the MD.
Enabling CFM CCM on ALU 7x50 PE1 router#--------------------------------------------------
echo 'Eth-CFM Configuration'
#--------------------------------------------------
 eth-cfm
 domain 1 name 'Provider_Domain' level 3
 association 1 format string name 'MA_VPLS_50'
 bridge-identifier 50
 exit
 ccm-interval 1
 remote-mepid 2
 remote-mepid 3
 exit
 exit
 exit

In above example, bridge-identifier identifies the service in which the MA is deployed. The remote-mepid represents the list of IDs for all remote MEPs that belong to this MA.
After MD and MA are created, the MEP can be created under the VPLS or E-pipe service instance.
Creating MEP under VPLS 50 on PE1 router#--------------------------------------------------
echo 'Service Configuration'
#--------------------------------------------------
 service
 customer 1 create
 description 'Default customer'
 exit
 vpls 11 customer 1 create
 sap lag-1:4093 create
 description 'To CE1 Router'
 eth-cfm
 mep 1 domain 1 association 1 direction up
ccm-enable
no shutdown
exit
 exit
 exit
 mesh-sdp 12:11 create
 exit
 mesh-sdp 13:11 create
 exit
 no shutdown
 exit
 exit

The following example shows enabling CFM for a Customer domain for VLAN 100 on Cisco devices.
Configuring CFM CC on Cisco deviceethernet cfm domain Customer_Domain level 7
!
ethernet cfm enable
ethernet cfm cc level 7 vlan 100 interval 20 loss-threshold 3
!
interface gigabitethernet 3/1
ethernet cfm mep level 7 outward mpid 111 vlan 100
!

MIPs in CFM
MIPs are intermediate points in the CFM architecture. A MIP responds to an LBM message with an LBR message if its own MAC address is the destination address of the LBM message. A MIP forwards upon receiving LTM messages based on FDB lookup, and responds with an LTR message. A MIP is transparent to CCM messages.
In ALU device, a MIP is automatically created with a MEP using the command mhf-creation explicit. 
Adding a MIP to a VPLS service in ALU device#--------------------------------------------------
echo 'Eth-CFM Configuration'
#--------------------------------------------------
 eth-cfm
 domain 1 name 'Provider_Domain' level 3
 association 1 format string name 'MA_VPLS_50'
 bridge-identifier 50
mhf-creation explicit
 exit
 ccm-interval 1
 remote-mepid 2
 remote-mepid 3
 exit
 exit
 exit

In a Cisco device, a MIP is created under the interface as below:
Adding a MIP in Cisco deviceinterface gigabitethernet 3/1
ethernet cfm mip level 7
!

The loopback address is only used by the computer you're on, and only for special circumstances—unlike a regular IP address that transfers files to and from other networked devices. For example, a web server running on a computer can point to 127.0.0.1 so that the pages run locally and test before it's deployed.
I had created multiple Loopback virtual devices that had QuickTime in them and even though I had Mute when capturing turned on, I had a Monitor set to my display and of course, it was slightly delayed from the normal speaker output on my Mac.
The purpose of a MAC address is to distinguish individual devices on the media (it is a link local layer 2 address). Since the loopback interface is by definition not connected on any physical media there is no purpose in a link local address and MAC addresses are not supported on loopback interfaces.
When you install a loopback adapter, the loopback adapter assigns a local IP address for your computer.
After the loopback adapter is installed, there are at least two network adapters on your computer: your own network adapter and the loopback adapter. To run Oracle Database on Windows, set the loopback adapter as the primary adapter. 
You can change the bind order for the adapters without reinstalling the loopback adapter. The bind order of the adapters to the protocol indicates the order in which the adapters are used. When the loopback adapter is used first for the TCP/IP protocol, all programs that access TCP/IP first probe the loopback adapter. The local address is used for tools, such as Oracle Enterprise Manager. Any other applications that use a different Ethernet segment are routed to the network card. 
Loopback Mac FreeA loopback adapter is required if:
You are installing on a non-networked computer and plan to connect the computer to a network after installation.
Checking if a Loopback Adapter is Installed on Your Computer
To check if a loopback adapter is installed on your computer, run the ipconfig /all command: 
Installing a Loopback Adapter on Windows 7
Use this procedure to install a loopback adapter on Windows 7. 
Installing Microsoft KM-TEST Loopback Adapter on Windows 8, Windows 8.1, Windows Server 2012, and Windows Server 2012 R2
Use this procedure to install Micrsoft KM-TEST loopback adapter on different Windows versions. 
Removing a Loopback Adapter
Use this procedure to remove a loopback adapter. 
Related Topics
Checking if a Loopback Adapter is Installed on Your ComputerTo check if a loopback adapter is installed on your computer, run the ipconfig /all command: 
Note:

Loopback Adapter installed on the computer must be made the Primary Network Adapter.
Loopback Mac DownloadIf there is a loopback adapter installed, then see a section that lists the values for the loopback adapter. Keykey 2 5 – typing tutor. For example:
Installing a Loopback Adapter on Windows 7Use this procedure to install a loopback adapter on Windows 7.
To install a loopback adapter on Windows 7: 
Loopback Mac CrackedClick Start and enter hdwwiz in the Search box. 
Click hdwwiz to start the Add Hardware wizard. 
In the Welcome window, click Next. 
In the The wizard can help you install other hardware window, select Install the hardware that I manually select from a list, and click Next. 
From the list of hardware types, select the type of hardware you are installing, select Network adapters, and click Next. 
In the Select Network Adapter window, make the following selections:
Manufacturer: Select Microsoft. 
Network Adapter: Select Microsoft Loopback Adapter. 
Click Next. 
In the The wizard is ready to install your hardware window, click Next. 
In the Completing the Add Hardware Wizard window, click Finish. 
Click Manage Network Connections. This displays the Network Connections Control Panel item. 
Right-click the connection that was just created. This is usually named 'Local Area Connection 2'. Choose Properties. 
On the General tab, select Internet Protocol (TCP/IP), and click Properties. 
In the Properties dialog box, click Use the following IP address and do the following: 
IP Address: Enter a non-routable IP for the loopback adapter. Oracle recommends the following non-routable addresses: 
192.168.x.x (x is any value between 0 and 255) 
10.10.10.10
Subnet mask: Enter 255.255.255.0. 
Record the values you entered, which you need later in this procedure.
Leave all other fields empty.
Click OK. 
Click Close. 
Close Network Connections. 
Restart the computer.
Add a line to the DRIVE_LETTER: WINDOWSsystem32driversetchosts file with the following format, after the localhost line: 
where:
IP_address is the non-routable IP address you entered in step 13. 
hostname is the name of the computer. 
domainname is the name of the domain. 
For example:
Check the network configuration:
Open System in the Control Panel, and verify that Full computer name displays the host name and the domain name, for example, sales.us.example.com. 
Click Change. In Computer name, you must see the host name, and in Full computer name, you must see the host name and domain name. Using the previous example, the host name is now sales and the domain name us.example.com. 
Click More. In Primary DNS suffix of this computer, you must see the domain name, for example, us.example.com. 
Installing Microsoft KM-TEST Loopback Adapter on Windows 8, Windows 8.1, Windows Server 2012, and Windows Server 2012 R2Use this procedure to install Micrsoft KM-TEST loopback adapter on different Windows versions.
Loopback Audio For WindowsTo install a loopback adapter on Windows 8, Windows 8.1, Windows Server 2012, or Windows Server 2012 R2, perform the following steps:
Open the Windows Control Panel.
Double-click Add Hardware to start the Add Hardware wizard.
In the Welcome window, click Next.
In the The wizard can help you install other hardware window, select Install the hardware that I manually select from a list, and click Next.
From the list of hardware types, select the type of hardware you are installing, select Network adapters, and click Next.
In the Select Network Adapter window, make the following selections:Manufacturer: Select Microsoft. 
Network Adapter: Select Microsoft KM-TEST Loopback Adapter. 
Then continue with the same steps as given for Windows Server 2008.
Removing a Loopback AdapterUse this procedure to remove a loopback adapter.
Loopback Audio SoftwareTo remove a loopback adapter, perform the following steps:
Display System in the Windows Control Panel.
In the Hardware tab, click Device Manager. This tab is not available with Windows Server 2008. Click Device Manager instead. 
In the Device Manager window, expand Network adapters. You must see Microsoft Loopback Adapter.
Right-click Microsoft Loopback Adapter and select Uninstall. In Windows 8, Windows 8.1, Windows Server 2012, or Windows Server 2012 R2, right-click Microsoft KM-TEST Loopback Adapter and select Uninstall. 
Click OK.
Restart the computer.
Remove the line from the DRIVE_LETTER:WINDOWSsystem32driversetchosts file, added after the localhost line while installing the loopback adapter on other Windows operating systems.