Configurable Logging; Flexible Vlan Tagging For Cfm - Cisco NCS 5500 Series Configuration Manual

Ethernet CFM
IEEE 802.1ag and ITU-T Y.1731 define slightly different linktrace mechanisms. In particular, the use of
Note
the CCM learning database and the algorithm described above for responding to LTM messages are
specific to IEEE 802.1ag. IEEE 802.1ag also specifies additional information that can be included in
LTRs. Regardless of the differences, the two mechanisms are interoperable.

Configurable Logging

CFM supports logging of various conditions to syslog. Logging can be enabled independently for each service,
and when the following conditions occur:
• New peer MEPs are detected, or loss of continuity with a peer MEP occurs.
• Changes to the CCM defect conditions are detected.
• Cross-check "missing" or "unexpected" conditions are detected.
• AIS condition detected (AIS messages received) or cleared (AIS messages no longer received).
• EFD used to shut down an interface, or bring it back up.

Flexible VLAN Tagging for CFM

The Flexible VLAN Tagging for CFM feature ensures that CFM packets are sent with the right VLAN tags
so that they are appropriately handled as a CFM packet by the remote device. When packets are received by
an edge router, they are treated as either CFM packets or data packets, depending on the number of tags in
the header. The system differentiates between CFM packets and data packets based on the number of tags in
the packet, and forwards the packets to the appropriate paths based on the number of tags in the packet.
CFM frames are normally sent with the same VLAN tags as the corresponding customer data traffic on the
interface, as defined by the configured encapsulation and tag rewrite operations. Likewise, received frames
are treated as CFM frames if they have the correct number of tags as defined by the configured encapsulation
and tag rewrite configuration, and are treated as data frames (that is, they are forwarded transparently) if they
have more than this number of tags.
In most cases, this behavior is as desired, since the CFM frames are then treated in exactly the same way as
the data traffic flowing through the same service. However, in a scenario where multiple customer VLANs
are multiplexed over a single multipoint provider service (for example, N:1 bundling), a different behavior
might be desirable.
Interface and Hardware Component Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release
6.1.x
36
Configuring Ethernet OAM