VMG1312-B Series User’s Guide 284
CHAPTER 35
Diagnostic
35.1 Overview
The Diagnostic screens display inform at ion t o help you ident ify problem s wit h the Device.
The route between a CO VDSL sw itch and one of it s CPE m ay go t hrough swit ches owned by
independent organizat ions. A connect ivit y fault point generally takes tim e to discover and im pacts
subscriber’s network access. I n order to elim inate t he m anagem ent and m aint enance efforts, I EEE
802.1ag is a Connect ivit y Fault Managem ent ( CFM) specification which allows network
adm inistrators t o identify and m anage connect ion fault s. Thr ough discovery and verification of t he
pat h, CFM can detect , analyze and isolate connectivit y fault s in bridged LANs.
35.1.1 What You Can Do in this Chapter
• The Pin g & Tr aceRout e & N sLookup screen let s you ping an I P address or t race t he rout e
packet s take t o a host (
Section 35.3 on page 285) .
• The 8 0 2 .1 a g screen lets you perform CFM actions (
Section 35.5 on page 287).
• The OAM Ping Test screen let s you send an ATM OAM ( Operat ion, Adm inist ration and
Maintenance) packet to verify t he connect ivity of a specific PVC. ( Section 35.5 on page 287) .
35.2 What You Need to Know
The following t erm s and concept s m ay help as you read through this chapt er.
How CFM Works
A Maintenance Association ( MA) defines a VLAN and associated Maint enance End Point (MEP) port s
on the device under a Maint enance Dom ain ( MD) level. An MEP port has t he abilit y t o send
Connect ivity Check Messages ( CCMs) and get other MEP port s inform at ion from neighbor devices’
CCMs w ithin an MA.
CFM provides t wo tests to discover connect ivity faults.
• Loopback t est - checks if t he MEP port receives it s Loop Back Response ( LBR) from its target
aft er it sends the Loop Back Message ( LBM). I f no response is received, there m ight be a
connectivit y fault between t hem .
• Link trace test - provides additional connectivity fault analysis t o get m ore inform ation on where
the fault is. I f an MEP port does not respond to the source MEP, this m ay indicate a fault .
Adm inist rators can t ake furt her act ion t o check and resum e services from t he fault according to
the line connectivit y st at us report.
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