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I have just taken control of a small-ish company network (1 server, 60 workstations) They have been experiencing periodic file server dropouts, and I just came across this situation:

  • The internet router is handling DHCP (Which will be moved to a server soon)
  • It is set to handout IPs from 192.168.1.9 to ...254 (soon to change to .11)
  • It is set with a Lease time of 6000 seconds

The server (Which is the DC & file server - again this will change soon!!!) is manually set to 192.168.1.10.

So, is it feasible that these dropouts are caused by the fact that DHCP doesnt know about the server, which has a fixed IP but is within its dynamic pool? I assume DHCP doesn't check if the address its about to hand out actually IS free?

Digital Lightcraft
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  • If DHCP interfering with network connectivity, you should be able to observe the issue by listening network interfaces of File Server and clients. – Aesnak Mar 23 '17 at 13:24

2 Answers2

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The DHCP may hand out 192.168.1.10 without checking the network, yes. It doesn't have any way to verify what is out of its control. That's why you should have only one dhcp server (per ip range) and keep your fixed ip addresses out of its range, or add reservations within the DHCP config for the machines you wish to keep fixed.

Andy
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If the DHCP hands out an IP address of 192.168.1.10 to some device on the network, then it will cause issues. The issue is that two devices on the network will have the same IP address, and the other devices will try to connect to either one when they try to connect to 192.168.1.10.

You should change the DHCP IP address space to start from 192.168.1.11.

Tero Kilkanen
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