Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Software Configuration Guide, Release 12.2(33)MRB
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Chapter 4 Configuring the Cisco MWR 2941 Router Using the CLI
Configuration Sequence
Continuity Check Messages
CFM CCMs are multicast heartbeat messages exchanged periodically among MEPs. They allow MEPs
to discover other MEPs within a domain and allow MIPs to discover MEPs. CCMs are confined to a
domain and S-VLAN.
CFM CCMs have the following characteristics:
• Transmitted at a configurable periodic interval by MEPs. The interval can be from 10 seconds to
65535 seconds, the default is 30.
• Contain a configurable hold-time value to indicate to the receiver the validity of the message. The
default is 2.5 times the transmit interval.
• Catalogued by MIPs at the same maintenance level.
• Terminated by remote MEPs at the same maintenance level.
• Unidirectional and do not solicit a response.
• Carry the status of the port on which the MEP is configured.
Loopback Messages
CFM loopback messages are unicast frames that a MEP transmits, at the request of an administrator, to
verify connectivity to a particular maintenance point. A reply to a loopback message indicates whether
a destination is reachable but does not allow hop-by-hop discovery of the path. A loopback message is
similar in concept to an Internet Control Message Protocol (ICMP) Echo (ping) message.
A CFM loopback message can be generated on demand using the CLI. The source of a loopback message
must be a MEP; the destination may be a MEP or a MIP. CFM loopback messages are unicast; replies
to loopback messages also are unicast. CFM loopback messages specify the destination MAC address,
VLAN, and maintenance domain.
Traceroute Messages
CFM traceroute messages are multicast frames that a MEP transmits, at the request of an administrator,
to track the path (hop-by-hop) to a destination MEP. They allow the transmitting node to discover vital
connectivity data about the path, and allow the discovery of all MIPs along the path that belong to the
same maintenance domain. For each visible MIP, traceroute messages indicate ingress action, relay
action, and egress action. Traceroute messages are similar in concept to User Datagram Protocol (UDP)
traceroute messages.
Traceroute messages include the destination MAC address, VLAN, and maintenance domain and they
have Time To Live (TTL) to limit propagation within the network. They can be generated on demand
using the CLI. Traceroute messages are multicast; reply messages are unicast.
Cross-Check Function
The cross-check function is a timer-driven post-provisioning service verification between dynamically
discovered MEPs (via CCMs) and expected MEPs (via configuration) for a service. The cross-check
function verifies that all endpoints of a multipoint or point-to-point service are operational. The function
supports notifications when the service is operational; otherwise it provides alarms and notifications for
unexpected endpoints or missing endpoints.
The cross-check function is performed one time. You must initiate the cross-check function from the CLI
every time you want a service verification.