AX/DX/EX/PX Series User’s Guide
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CHAPTER 44
Diagnostic
44.1 Diagnostic Overview
The Diagnostic screen displays information to help you identify problems with the Zyxel Device.
The route between an Ethernet 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.
44.1.1 What You Can Do in this Chapter
• The Ping&Traceroute&Nslookup screen lets you ping an IP address or trace the route packets take to
a host (Section 44.3 on page 498).
• The 802.1ag screen lets you perform CFM actions (Section 44.4 on page 499).
• The 802.3ah screen lets you configure link OAM port parameters (Section 44.5 on page 500).
• The OAM Ping screen lets you send an ATM OAM (Operation, Administration and Maintenance)
packet to verify the connectivity of a specific PVC (Section 44.6 on page 501).
44.2 What You Need to Know
The following terms and concepts may help as you read through this chapter.
How CFM Works
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.
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