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18.1 Dia g no stic O ve rvie w
The
Dia g no stic
The route between a Central Office Very-high-bit-rate Digital Subscriber Line (CO VDSL) switch and one
of its Customer-Premises Equipment (CPE) may go through switches owned by independent
organizations. A connectivity fault point generally takes time to discover and impacts subscriber's
network access. In order to eliminate the management and maintenance efforts, IEEE 802.1ag is a
Connectivity Fault Management (CFM) specification which allows network administrators to identify
and manage connection faults. Through discovery and verification of the path, CFM can detect,
analyze and isolate connectivity faults in bridged LANs.
18.1.1 Wha t Yo u C a n Do in this C ha pte r
• The
Ping & T ra c e Ro ute
(Section 18.3 on page
18.2 Wha t Yo u Ne e d to Kno w
The following terms and concepts may help as you read through this chapter.
Ho w C FM Wo rks
A Maintenance Association (MA) defines a VLAN and associated Maintenance End Point (MEP) ports
on the device under a Maintenance Domain (MD) level. An MEP port has the ability to send
Connectivity Check Messages (CCMs) and get other MEP ports information from neighbor devices'
CCMs within an MA.
CFM provides two tests to discover connectivity faults.
• Loopback test - checks if the MEP port receives its Loop Back Response (LBR) from its target after it
sends the Loop Back Message (LBM). If no response is received, there might be a connectivity fault
between them.
• Link trace test - provides additional connectivity fault analysis to get more information on where the
fault is. If an MEP port does not respond to the source MEP, this may indicate a fault. Administrators
can take further action to check and resume services from the fault according to the line
connectivity status report.
screens display information to help you identify problems with the WX Device.
screen lets you ping an IP address or trace the route packets take to a host
151).
WX Series User's Guide
C
HA PTER
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