Troubleshooting guide

Contents
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Bad Upstream Signal-to-noise Ratio Detected 58
Upstream Power Level Too Low or High 61
Resolving Problems on the Downstream Path 63
Bad Downstream Signal-to-Noise Ratio Detected 64
Downstream Power Level Too Low or High 65
Resolving Cable Modem Problems 67
Misconfigured Authentication String or Key 67
CM Does Not Reply to Station Maintenance Requests 69
CM is Offline 70
CM Cannot Obtain an IP Address 72
Provisioning Problems Cause CMs Not to Register 74
CM Does Not Respond to SNMP Messages 77
5 Troubleshooting TCP/IP
Introduction 81
Resolving Host Connectivity Problems 81
Default Gateway Configuration Problems 81
Misconfigured or Missing Default Routes 82
Incomplete DNS Host Table 83
DNS Not Running 84
Handling Routing Problems 84
Problem Router 84
Misconfigured Router 86
Routing Interface Down 87
Handling a Misconfigured Access List 89
Access List and Filter Misconfigurations 91
Handling UDP Broadcast Forwarding Problems 92
Missing or Misconfigured IP Helper-address Specification 92
UDP Broadcast Misconfiguration 93
Resolving PPP Link Over SONET Failures 94
6 Troubleshooting RIP
Introduction 99
Handling Routing Table Problems 99