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Beginner

DHCP issue with VLANS

Hello,

I have a stack of SG500 switches that are currently in L3 mode and I am using at the default gateway for my networks. The IP to this switch stack is 10.20.30.254 VLAN1, 10.20.40.254 VLAN40, 10.10.10.254 VLAN10. I am also running Server 2012 R2 as my DHCP server and I have scopes setup for each of these VLANs. 

On the switch I have relay turned on, 10.10.10.10 added to the DHCP servers list and I have added each VLAN interface into the "interface" section.

All was going well until about 3 weeks ago when on Monday mornings, the DHCP leases would expire and couldn't get a new lease. Rebooting the switch would fix it temporarily until the next time the leases expire and then it was a fire drill all over again.

I have been using this setup for about 2 years now and I haven't had any issues with it until a few weeks ago. I have a couple of LAGs setup on the switch for my server. This is where I think the configuration might be a little messed up. I have the LAGs untagged VLAN10 and tagged VLANs for 1 and 40. The switchports are setup as trunks so not sure if somehow this is affecting how things are flowing. Wanted to get some advise before I just start changing the config.

Thanks in advance!

Sean

Everyone's tags (2)
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Explorer

On trunked ports only the

On trunked ports only the default VLAN will pass untagged traffic.  Years ago when I was working I always setup the server ports as access ports LAG or not.  I like keeping all the VLAN traffic managed by the Cisco hardware but this is not a requirement.

If your network has been running for 2 years then I would look for what has changed in the last 2 weeks.  Something must of changed to make it stop working.

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Beginner

Got a little bit of an update

Got a little bit of an update:

At 11AM this morning, I had several MacBooks where their leases expired and then wouldn't pull a new lease. I disabled DHCP on the Windows server and setup the switches to handle DHCP. That didn't work so I ended up reconfiguring the SSID to use Meraki DHCP instead which did work. I'll leave it like that for the time being as it is buying me some breathing room.

The switchports that the Merakis are plugged into are trunk ports with untagged VLAN10 and tagged VLAN40. Should I also switch these to access ports?

Highlighted
Explorer

I have run in the past a

I have run in the past a Microsoft DHCP server with over 2000 leases on a Cisco network using IP helper address which DHCPRELAY should work the same.  The server was setup on access ports not trunked ports.

Highlighted
Explorer

Your wireless should be setup

Your wireless should be setup on a trunked port since you are using multiple VLANs.  I assume you are assigning an SSID  to a VLAN and you have more than one.

Using DHCP off a wireless device can be a positive security feature for guest networks or foreign devices.  It can be a problem if you want to access internal hosts.