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Troubleshooting
Ideal HFC Plant Configuration Issues
151
Cable Modem Cannot Establish IP Connectivity
If a cable modem cannot establish IP connectivity, the cause might be one or more of the
following :
! The DHCP server could not be accessed because the network is down.
! The DHCP server is down. Ping the DHCP server IP address using the ping command to
see if the server is responding.
! The DHCP server parameters are not properly configured within the CMTS.
A high IM value in the flap list can be an indication of DHCP setup issues.
Cable Modem Cannot Successfully Register
If a cable modem cannot successfully register, the cause might be one or more of the
following:
! The cable modem did not receive a configuration file because:
! The TFTP server could not be accessed because the network is down.
! The TFTP server is down.
! The name of the configuration file provided in the DHCP response was incorrect.
! The TFTP server IP address provided in the siaddr field of the DHCP response was
incorrect.
! The TFTP server was hosting the maximum number of sessions when the cable
modem requested the configuration file.
! The CMTS indicated an authentication failure in its REG-RSP message because:
! The TFTP Server Timestamp field in the cable modem’s REG-REQ message differs
from the local time maintained by the CMTS by more than the CM Configuration
Processing Time (the maximum time for a cable modem to send a REG-REQ
message following the receipt of the configuration file, which must be a minimum
of 30 seconds).
! The TFTP Server Provisioned Modem Address field in the cable modem’s REG-REQ
message does not match the requesting cable modem’s actual address.
! The message integrity check (MIC) was not valid because the shared secret between
the CMTS and the provisioning server did not match, which results in an
authentication failure.
! The MIC was not valid because the configuration file was modified en route
between the provisioning server and the cable modem.
Issue the show log cable command to see if the CMTS made an entry for an
authentication failure in the local event log.