Problem with DHCP over VLAN and WiFi

Problem with DHCP over VLAN and WiFi

Problem with DHCP over VLAN and WiFi
Problem with DHCP over VLAN and WiFi
Tuesday
Model: ER707-M2   EAP225   SG2210P  
Hardware Version:
Firmware Version: Latest

I have come across a problem with DHCP on my Omada system, when the DHCP Server Service is provided by External Equipment. A diagram of the scenario is shown here

Diagram

 

The Omada system handles the DHCP duties for the default subnet (VLAN 1), while a seperate DHCP server (from pfSense here but other Linux variants have also been tested) provides the IP address pools for VLANS 2 and 3. Each VLAN is configured with Legal DHCP Server address set to the eth0.2 or eth0.3 of the DHCP Server

 

If the computer connect to ports 3, 4 or 5 of the switch, it gets an IP address.

If the computer connects to port 6 and sets the VLAN tag to 2 or 3, it gets an IP address for the corresponding subnet.

 

If the computer connects to either SSID2 or SSID3 on the access point, no IP address is provided. Some further analysis is provided.

  1. With SSID connection, using the packet tracing function on the EAP, we see the DHCPDISCOVER being received from the computer, but no DHCPOFFER - somewhere the offer is lost. 

EAP Wireless side

Wirless capture

 

EAP Wired side

EAP Wired capture

 

2. When connected to the the Tagged Ethernet switch port we see all the right things (VLANID 1010)

Wirded DHCP on VLAN 1010 OK

 

 

Does anyone know why DHCP over WiFi is failing when the DHCP Server is on a VLAN, but DHCP over Ethernet to the same DHCP Server is OK??

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#1
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5 Reply
Re:Problem with DHCP over VLAN and WiFi
Tuesday

Hi @Paul_Higgs,

 

  • Am I correct to assume that SSID2/3 are mapped to use VLAN2/3 respectivly?
  • Are VLAN 2/3 are both tagged members on port 8?

 

 

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#2
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Re:Problem with DHCP over VLAN and WiFi
22 hours ago

  @D-C 

 

Yes, SSID 2/3 are mapped to VLAN 2/3 respectively.

Yes, VLAN 2/3 are both tagged members on port 8.

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#3
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Re:Problem with DHCP over VLAN and WiFi
21 hours ago

  @Paul_Higgs 

 

Do you have DHCP relay configured on the gateway or any switches for any of the vlans?

Have you enable "Legal DHCP Servers" on the gateway, possibly with incorrect entries?

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#4
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Re:Problem with DHCP over VLAN and WiFi
18 hours ago

  @GRL 

 

I don't have DHCP relay configured. The Omada domain doesn't even have an IP address for VLANS 2 or 3 since it should only operate in the switching domain.

 

I tried both with and without "Legal DHCP Servers" being defined for VLANS 2 and 3, however it makes no difference.

 

The main consideration here is that wired Ethernet functions OK in both tagged and untagged access to VLANs 2 and 3, however WiFI/SSID access to the VLANs does not.

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#5
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Re:Problem with DHCP over VLAN and WiFi
17 hours ago

@Paul_Higgs, I don't have the TPLink router, but I do use the switches and APs with pfSense and have not had any issues. Can you plug the AP into port 6 and try?

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#6
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