MX 84 DHCP Relay slow with on Non-Native VLAN Windows 2016

lesbarn
Here to help

MX 84 DHCP Relay slow with on Non-Native VLAN Windows 2016

I just setup a Windows 2016 Standard Server running DHCP for our network of two VLANS native 10.6.1.x /24 and other 10.6.2.x/24 The DHCP server sets on the native VLAN and works perfect for all clients. I have set DHCP relay on the 10.6.2.x VLAN and pointed it to the DHCP server on the native VLAN. The issue I am having is very slow IP assignment to (up to five minutes or not at all on the Chromebooks)  Mac OS clients,  iOS clients,  and ChromeOS clients. I did a packet capture and saw the request for an IP address. Five minutes later it finally assigned an address, but it was different than the first one that was offered.This does not happen for Windows Clients. I tested one this morning and it had a fresh new IP even before I signed onto the computer. Any ideas? My network is very small so I could go back the way I had it and have the MX do the DHCP. I went through yesterday's DHCP server log and found it had issued 1790 NACK during a 24 hour period. All of these NACK relate to the 10.6.2.x/24 which is the VLAN having DHCP relayed by the MX 84. Thanks for reading.

10 REPLIES 10
DCooper
Meraki Alumni (Retired)

Are you going over the VPN tunnel? Is the windows server on a trunk port or access port if it is local?

No VPN tunnel is being used. The server is onsite plugged into a Meraki ms220-8P switch and yes the Windows server is on a trunk port. I doubled check the trunk port this morning.

DCooper
Meraki Alumni (Retired)

Turn it into a access port to see if that helps.


@DCooperwrote:

Turn it into a access port to see if that helps.


Is this a polite way of saying that all MS220-8P ports should be left at the default Trunk setting? It might account for some some of the poor streaming performance I experience . . .

Robin St.Clair | Principal, Caithness Analytics | @uberseehandel

If I am dealing with two VLANs doesn't the server need to be on a trunk port?
DCooper
Meraki Alumni (Retired)

Are you tagging an LAN port on your server? DHCP relay is a broadcast to the MX then a unicast when it does the relay to the server.

 

If your trunking the same VLAN you have IP-helper setup for that would be your issue. You can choose one or the other, either trunk it or relay it but can't do both.

My set up is VLAN 10 Native and VLAN 20. The DHCP server is on VLAN 10 and both VLANs can communicate with each other. The only reason I created the VLANs was to add more addressing. I just turned off DHCP relay on VLAN 20 and now my event log says DHCP Problem no offers received vap 0, vlan 20. Any ideas?
DCooper
Meraki Alumni (Retired)

You may have something wrong with the VLAN configuration on the ports?

 

Please PM a link to your organization/network.

 

Can you tell me which port the server is on and which device/port that is on VLAN 20 your trying to get an address from?

I did lots of reading over the last few days and the main theme I discovered was interface on a trunk and use DHCP relay on non native VLANs. I decided to use my other server which is a better computer with an Intel NIC. Once I set DHCP relay on the MX84 it worked instantly. The issue had to be something with the NIC on the other machine. I will continue to test this setup over the weekend.and give hopefully one final post to make confirm this setup is working.

Well, I spoke to soon. It was a big mess. I ended up calling Meraki and they said the problem is the DHCP server offering NACKs to both VLAN clients for no apparent reason. His response was "I see NACKs everywhere.." Now I am back to the MX doing the DHCP. I do appreciate the responses.

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