I'm trying to configure a small business network with one Cisco SG200-26, a Linux server and two TP-Link TL-WA801ND.

I have set up the APs to have two different SSIDs, Public and Staff, and have configured VLAN tagging with tags 5 & 6 respectively.

On the switch, I have created the VLANs and configured the server port and the AP ports to trunk.

I've configured the server to have the two VLAN networks with IP addresses, eth0.5 & eth0.6. The DHCP server is configured to give addresses on the correct subnets.


eth0 has
eth0.5 has
eth0.6 has

Now, the APs receive management IP addresses via DHCP in

I see connected devices requesting IP addresses (from server log):

Apr 12 13:08:33 server dhcpd: DHCPDISCOVER from 60:d8:19:xx:xx:xx (pc1) via eth0.5
Apr 12 13:08:33 server dhcpd: DHCPOFFER on to 60:d8:19:xx:xx:xx (pc1) via eth0.5

But I don't see them accepting the address. Suggestions welcome, I'm stumped!

  • Can you run wireshark on a client to see if they get a response from the server? Can they ping the server with a static ip configured? – GerryEgan Apr 13 '13 at 15:12
  • I'm remote administering the office at the moment, so I can't check either of these things. I have changed the AP to set the Staff VLAN tag to 1, and this then enables connected PCs to get an IP address. That'll do for the moment, until I can drop in and do some more diagnostics. Would the PCs have to support VLAN tagging? – AlexW Apr 15 '13 at 14:20
  • Ok, I've run wireshark, and no response from the server is received. This particular client is Windows 8, if that makes a difference. With a manual IP address set, pings from client to server work. Pings from server to client are seen in wireshark, but the response does not get back to the server. I'm now wondering if it's a firewall issue on the server. Packets are clearly getting through! – AlexW Apr 17 '13 at 21:15
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    check if your switch has 'DHCP Helper' addresses you can set for the VLANs. Our brocade switches require this to be set to the IP of your DHCP server so DHCP requests can be properly forwarded across VLANS. – Lee Harrison Aug 5 '15 at 16:07

Check if there are settings for DHCP snooping on the switch and access points. It is possible that switch will suppress DHCP traffic unless you specify particular ports as DHCP trusted.


Might be better to put the server on its own subnet and use ip-helper on the switch vlan interface to provide IP addresses from the dedicated server IP/subnet

  • the most probably this would not be an issue. Anyway if the server act only as DHCP server and not a router it may have just a "management" IP and via IP-helper the request from other VLANs can be handled... Anyway DHCP snooping seems to be in place based on the description. – Kamil J Dec 4 '18 at 16:06

You may need:


in your VLAN interfaces configuration so that DHCP server correctly recognizes and answers the queries.

This is what I have in ifcfg-<iface>.<vlan> in CentOS 8. Adjust as necessary for your distro.

Reload the interfaces and the DHCP server for the settings to take effect.

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