Service Manual

• routing protocols choose a subset of the total network topology for forwarding, making it hard to detect faults in links and
nodes that are not included in the active routing topology. This is made more complex when using some form of traffic
engineering (TE) based routing.
• network and element discovery and cataloging is not clearly defined using IP troubleshooting tools.
There is a need for Layer 2 equivalents to manage and troubleshoot native Layer 2 Ethernet networks. With these tools, you can
identify, isolate, and repair faults quickly and easily, which reduces operational cost of running the network. OAM also increases
availability and reduces mean time to recovery, which allows for tighter service level agreements, resulting in increased revenue
for the service provider.
In addition to providing end-to-end OAM in native Layer 2 Ethernet Service Provider/Metro networks, you can also use CFM to
manage and troubleshoot any Layer 2 network including enterprise, datacenter, and cluster networks.
Maintenance Domains
Connectivity fault management (CFM) divides a network into hierarchical maintenance domains, as shown in the following
illustration.
A CFM maintenance domain is a management space on a network that a single management entity owns and operates. The
network administrator assigns a unique maintenance level (from 0 to 7) to each domain to define the hierarchical relationship
between domains. Domains can touch or nest but cannot overlap or intersect as that would require management by multiple
entities.
Figure 3. Maintenance Domains
Maintenance Points
Domains are comprised of logical entities called maintenance points.
A maintenance point is an interface demarcation that confines CFM frames to a domain. There are two types of maintenance
points:
• Maintenance end points (MEPs) — a logical entity that marks the end-point of a domain.
• Maintenance intermediate points (MIPs) — a logical entity configured at a port of a switch that is an intermediate point of a
maintenance entity (ME). An ME is a point-to-point relationship between two MEPs within a single domain. MIPs are internal
to a domain, not at the boundary, and respond to CFM only when triggered by linktrace and loopback messages. You can
configure MIPs to snoop continuity check Messages (CCMs) to build a MIP CCM database.
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