Changing DHCP Logging Options

The DHCP service can log DHCP service messages and DHCP transactions to syslog. See the syslogd(1M) and syslog.conf(4) manual pages for more information about syslog.

DHCP service messages logged to syslog include:

• Error messages, which notify the administrator of conditions that prevent the DHCP service from fulfilling a request by a client or by the administrator.

• Warnings and notices, which notify the administrator of conditions that are abnormal, but do not prevent the DHCP service from fulfilling a request.

You can increase information reporting by using the verbose option for the DHCP daemon. Verbose message output can be useful in troubleshooting DHCP problems. See "How to Generate Verbose DHCP Log Messages (DHCP Manager)".

Another useful troubleshooting technique is transaction logging. Transactions provide information about every interchange between a DHCP server or BOOTP relay and clients. DHCP server transactions include:

• ASSIGN -- IP address assignment

• EXTEND -- Lease extension

• RELEASE -- IP address release

• DECLINE -- Client declining address assignment

• INFORM -- Client requesting network configuration parameters but not an IP address

• NAK -- Server does not acknowledge a client's request to use a previously used IP address

• ICMP_ECHO -- Server detects potential IP address for offering is already in use by another host.

BOOTP relay transactions include:

• RELAY-CLNT -- Message being relayed from the DHCP client to a DHCP server

• RELAY-SRVR -- Message being relayed from the DHCP server to the DHCP client

Transaction logging is disabled by default. When enabled, transaction logging uses the local0 syslog facility by default. DHCP transaction messages are generated with a syslog severity level of notice, so by default transactions are logged to the file where other notices are logged. However, because they use a local facility, the transaction messages can be logged separately from other notices if you edit the syslog.conf file to specify a separate log file.

You can disable or enable transaction logging, and specify a different syslog facility, from 0 through 7, as explained in "How to Enable and Disable DHCP Transaction Logging (DHCP Manager)". If you edit the server system's syslog.conf file, you can also instruct syslogd to store the DHCP transaction messages in a separate file, as explained in "How to Log DHCP Transactions to a Separate Syslog File".