Ruckus DHCP Relay != Cisco/HP DHCP Relay

  • 1
  • Question
  • Updated 3 years ago
I'm working on configuring WLANs with vlan tagging.  My understanding of DHCP relay from my networking background is a way of relaying DHCP request between different vlans.  DHCP relay in the Ruckus world is a way of broadcast traffic management.  Can someone correct me if I'm wrong?

If I'm right, I'm running stuck.  I've trolled the forums for a while trying to find similar situations.  

DHCP server on vlan 10 and it has two scopes: main network: 10.0.0.0/16 (for vlan 10) and guest network: 10.1.0.0/16 (for vlan 20). I have an L3 switch that does the DHCP relay (using ip helper-address). Router is configured properly too.

I connect a laptop via wired connection to a port with a vlan assignment of 20  The laptop gets an IP address in the 10.1.0.0/16 subnet and all is well.  

I disconnect the wired and connect the wireless to a vlan 20 tagged WLAN and it doesn't get an IP address at all.  Wireshark shows no DHCP responses coming back.  

I configured the WLAN with Ruckus' DHCP relay per documentation and I get an address back in the 10.0.0.0/16 scope.

What doesn't make sense to me is if I have a WLAN with vlan tagging, shouldn't that be the same as plugging in a wired connection to a vlan tagged port?
Photo of Mark Buteyn

Mark Buteyn

  • 3 Posts
  • 0 Reply Likes

Posted 3 years ago

  • 1
Photo of Michael Brado

Michael Brado, Official Rep

  • 2183 Posts
  • 300 Reply Likes
Mark, you are on the right track. 

Two ideas come to mind.

Confirm that VLAN 20 is being trunked to the AP switch port, and that you are not tunneling the WLAN back to the ZD, unless you have VLAN 20 trunked to your ZD switch port.
Photo of Mark Buteyn

Mark Buteyn

  • 3 Posts
  • 0 Reply Likes
Thanks Michael.

I can confirm that vlan 20 is being trunked all the way.  Should have mentioned that the AP that I'm connecting to is plugged in to the same switch that I use for testing the wired connection I mentioned earlier.  If I set a static IP on the laptop's wireless connection all is well.  It just seems to be getting the DHCP back.

By tunneling, you are referring to Configure > WLANs > Edit SSID > Advanced Options > Tunnel Mode right?  That's checkbox is clear right now.
Photo of Eizens Putnins

Eizens Putnins

  • 107 Posts
  • 42 Reply Likes
As much as I understand, you try to get tagged WLAN adapter interface. For my understanding it is not possible (WLAN card doesn't support it), and this would be double tagging anyway.
When you mention connecting laptop to port in 20 VLAN through wired connection, what do you actually mean -- connecting to access port in VLAN 20 (than laptop interface is untagged), or to trunk with VLAN 20 tagged  (than laptop interface must be tagged by tag 20 -- it is supported by most modern cards)?

Anyway, WLAN AP (any, not specifically Ruckus) will just add VLAN tag 20 to traffic coming from WLAN assigned to VLAN 20. So when connecting to this WLAN you essentially connect to access port in VLAN 20.

If you are connecting properly, but it still doesn't work, check if you are connecting AP to proper port -- usually if you can't get DHCP, it means that proper VLAN isn't actually present on AP port, or VLAN isn't connected somewhere on trunks if there are multiple switches .
Hope it helps,
Eizens
Photo of Mark Buteyn

Mark Buteyn

  • 3 Posts
  • 0 Reply Likes
Thanks Eizens

Laptop wired is connecting to an access port in vlan 20.  The port is untagged in vlan 20.

Right, my understanding was that the AP adds the vlan tag and the WLAN is essentially an access port which is why I confused as to why I the DHCP relay works for wired access port but not the WLAN "access port".

Can anyone confirm that "DHCP Relay" means something different to Ruckus than it does to Cisco / HP?
Photo of Eizens Putnins

Eizens Putnins

  • 107 Posts
  • 42 Reply Likes
 It looks really surprising. I would propose to turn on packet capturing on this AP and look on Wireshark capture.
As you can communicate with fixed IP on laptop, than WLAN is connected properly to VLAN.
As you are getting proper DHCP IP in same VLAN on same switch through port, than DHCP relay is also working properly.
May be you have client isolation on and it prevents receiving DHCP messages?
Capture traffic on AP and look on this capture, that it must become clear.
Photo of Eizens Putnins

Eizens Putnins

  • 107 Posts
  • 42 Reply Likes
Hello, Mark,
You don't need  to set DHCP relay setting in Ruckus for WLANs, you may need it only if you have wired clients and DHCP server on multiple AP ports, configured with different subnets. Never needed it, so never used.
Otherwise Ruckus works as a bridge, and all DHCP relay setting must be done on wired side.

When you made capturing, it will be interesting what you found...

Regards,,
Eizens