DHCP

[IrfanKhan4904]

DHCP lease time 5 days is best for logs or can create issues in-network?

[Richard Burts · Accepted solution]

I do not understand your question. What relationship do you think there is between the length of the DHCP lease and logs? what kind of logs are you referring to?

What kind of issues in-network are you referring to?

What kind of environment is this? 

[IrfanKhan4904]

Internet usage logs against IP.

[Richard Burts]

Thanks for the clarification. But I am still not clear about what you are dealing with. If the question is about accurate identification of which specific machine is associated with a particular message in the system logs then I have several observations:

- how quickly do you look at the Internet usage logs? If you are looking at logs from today or yesterday I would be quite confident of machine identification. If logs are from a week ago I would be fairly confident of machine identification.  If logs are from a month ago I would be somewhat confident of machine identification.  If logs are from 6 months ago I might be worried about machine identification.

- in general longer leases allow you to be more accurate in machine identification. But you need to consider the volatility of membership in your network. If day after day, and week after week, and month after month the network is mostly the same machines then long leases are fine. But if a number of machines are transitory (show up in the network only briefly) then longer leases increase the possibility that you might exhaust the dhcp pool. So long leases might be problematic.

- given the usual behavior of dhcp that when a machine dhcp lease expires that it renews and gets the same address assigned, even logs from months ago are probably pretty safe about identifying which machine is involved.

- if accurate machine identification is really important, then perhaps you should not use dhcp but should use manual configuration of IP addresses. It would be more work for the network admins. But it would be the way to be sure of accuracy in machine identification.

[marce1000 · Accepted solution]

 - For users and or user-devices standard practice is to use a lease time of one day (86400 seconds) which corresponds to a cycle of activities so to speak. Sometimes standalone devices use DHCP too, such as a wireless access point. Then the lease time is usually set to a  longer period (a week for instance).

 M.