DHCP not issuing new addresses anymore

[Chipie]

I have an address pool of 8556, 2% currently in use

 

Address Pool

192.168.67.10 -

192.168.100.254

Subnet mask 255.255.0.0

A few Exclusions, a few reservations. Most items are currently on the 192.168.67.x range, there are 3 items on the 192.168.68.x range and 6 items on the 192.168.100.x range

 

Over the last few days we have had a few users complaining they can't get onto the network. I've noticed a couple of IP address clashes and a few machines have just not been able to get an IP address at all. When I add an address in manually, this seems to resolve the issue for a few of the users that I have tried this on. Lease duration is 12 hours.

 

It may be a coincidence, but I have had a few users complain about slow network.

 

Any ideas greatly appreciated as I'm banging my head against a brick wall.

[snagrat]

Firewall on the server?

[Chipie]

Nope .

[Davit2005]

What infrastructure do you have i.e.

 

Servers are they Virtual (what Hypervisor)?

Switch uplinks, Models etc?

 

There are a few points though

1) The default mask for 192.*.*.* is 255.255.255.0 . This unless I am wrong your 2 ranges are on same network, I guess 100 range is a VOIP or something

2) DHCP lease of only 12 hours is a bit short, we have our Guest Wifi on 3 hour lease everything else is on 3 days.

[andydis]

soo many questions ,

do you have VLANS?

do you have managed switches?

[Chipie]

Server is standard install (not Hypervisor).

Switches are all Netgear either GS724T, GS724 or GS716T.

Both ranges are on the same network, No VLANS. 100 Range is for printers

[Davit2005]

Could even be a dodgy printer causing issues seen that before.

[IrritableTech]

Can you run wireshark on the server to see if it is receiving DHCP requests? That might rule out firewalls and switch issues and allows you to concentrate your efforts. That's a huge scope and subnet by the way. DHCP is broadcast traffic, and there's a good chance the size of that scope is causing quite a bit of broadcast. Edited October 2, 2015 by IrritableTech

[Chipie]

Can you run wireshark on the server to see if it is receiving DHCP requests? That might rule out firewalls and switch issues and allows you to concentrate your efforts. That's a huge scope and subnet by the way. DHCP is broadcast traffic, and there's a good chance the size of that scope is causing quite a bit of broadcast.

 

Unfortunately its what I inherited. I will look to reduce the scope as we don't need anywhere near that amount of addresses. I have wireshark installed but never used it. Looks quite complicated. Any short youtube videos or guides you know that will guide me through how to test if the server is receiving DHCP requests?

[Chipie]

Unfortunately its what I inherited. I will look to reduce the scope as we don't need anywhere near that amount of addresses. I have wireshark installed but never used it. Looks quite complicated. Any short youtube videos or guides you know that will guide me through how to test if the server is receiving DHCP requests?

 

Wireshark is showing the server is receiving DHCP requests, BUT it seems to be only requesting on the 192.168.67.x range. Also showing destination as 255.255.255.255 which doesn't look right to me. Please see screen shot.

 

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