OUCS DHCP service: logs

With the introduction of new DHCP servers in early 2005, OUCS are pleased to be able to offer network administrators access to a subset of the server logs relating to their network.

Access is via a web interface, using the same password as for the DNS updates interface. Your network will only show in the list of networks if it is using the new servers; if your network has yet to migrate from the old servers you will not be able to use this facility.

Currently, two facilities are offered:

  • simple search: this allows you to search the logs for occurences of a given MAC address, IP address or client hostname.
  • dynamic pool information: this allows you to view the current, maximum and minimum usage of the dynamic pool on your network.

2. Dynamic pool information

Information regarding the usage of the dynamic pool on each subnet is gathered periodically from the DHCP server. The information displayed will typically be no more than a few minutes old.

Current usage will be displayed in terms of the number of available addresses out of the total number in the dynamic pool. Hosts with static IP addresses do not affect the count. Maximum and minimum usage is displayed from the previous Sunday onwards, i.e. a period of between seven and fourteen days.

3. Caveats

Remote access to server logs relies on constant communications between the DHCP servers themselves and the webserver. While TCP connections are used for reliability, it is still possible that the webserver will fail to receive information in the event of an extended network fault or system downtime. As such, we do not recommend that the absence of a log entry be relied upon as evidence in incidents such as displinary cases. Hostmaster can provide logs from the DHCP servers themselves if necessary; please contact networks@oucs.ox.ac.uk to request this.

It is also possible for temporary network faults to result in log entries from the two servers to appear out of sequence. At present the web interface does not correct for this problem.

Be aware that users may manually set their system's IP address to one from the dynamic pool. The DHCP servers will have no information regarding the systems doing this, and may attempt to lease the IP address in question to other clients. Savvy users may also assign arbitrary MAC addresses to their network interface. Such behaviour will often be against local network policy and appropriate action against users is recommended.

Written by IT Services. Latest revision 5 August 2014