DHCP issue inside a VM connected via wireless network

[gariup.guido]

Hi,

   I'm having the following problem. I have a notebook that associates to a WiFi (WLAN) netwok with a WLC 2106 that receive it's IP address from a DHCP server. When I turn on a virtual machine (with VMware o Virtual Box) inside that notebook, that VM doesn't receive an IP address from the DHCP server. The virtual network adapter that is inside the VM is configured as bridge mode, it is to say that it connects to the physical network through the notebook wireless adapter. Therefore, the AP and the WLC see the virtual machine and the notebook as they were two different clients, with two different MAC addresses but using the same physical network adapter. It's a very common scenario when you work with virtual machines.

   The question is. Could be any configuration inside de WLC that doesn't permit to lease more than one DHCP IP address to the same physical network adapter. Because if I configure an static IP address inside the VM it works OK. The problem is only receiveing a DHCP address.

Thanks.

Guido.

[Scott Fella]

Good to know! +5

Sent from Cisco Technical Support iPhone App

[gariup.guido]

Scott, Pat,

     What I don't understand why passive client feature would solve this problem (I couldn't test yet because I have version 4.2.112), beacause the configuration guide says that this feature will allow packets as ARP to be exchanged between the wired network and the wireless one. I think my problem is because what is posted in the links Scott wrote, where they say that this problem is beacuse the controller doesn't relay two DHCP request for the same wireless network card, although the source MAC addresses are different.

     However, I think the best workaround for this is to set the VMware network as NAT instead of bridge. But of course I will upgradethe controller software ir order to be able to test this passive client feature.

     Anyway, Scott and Pat, thank you very much for your help.

Thanks,

Guido.

[pcroak]

Hi Guido,

You are correct, configuring the VMware in NAT mode will also work for this scenario.

The passive client feature was enhanced in 7.0.116.0 to include support for 3rd party Workgroup Bridge devices. This support allowed multiple clients to pass traffic behind the bridge (using the wireless mac of the bridge). This WGB topology is effectively the same thing as having a VMware client behind a wireless NIC on the host.

-Pat

[chixson001]

Hello Folks,

This looks a few years dead, but it is still the most relevant search on Google for issues when getting an autonomous AP to relay DHCP. First, I will reinforce the desire to not run the VM in NAT mode for several reasons, the largest of which is performance.

I have had some new success when trying to get a VMFusion VM on my Mac to connect to my 3502i running 15.2(4)JA1, so here is the story:

Components-

New MBP Retina running Mavericks 

VMFusion 6 VM running Windows 7

Cisco 3502i running 15.2(4)JA1 

CenturyLink DSL Actiontec Q1000 modem

Synopsis-

MBP and all other devices have no problems getting an IP from the Q1000 (192.168.100.1/24 network). When a VM attempts to get an IP address, it fails. Wireshark running in the VM shows the Discover packets going out, but no Offer or Request being returned.

Solution-

Simply set up a DHCP scope on the Autonomous AP (NOTE: the DHCP scope needs to be the same network as what is being used for regular clients): http://www.cisco.com/c/dam/en/us/td/docs/wireless/access_point/15_2_4_JB/configuration/guide/scg15_2_4_JB3a.pdf . My commands included:

ip dhcp excluded-address 192.168.100.1 192.168.100.101     #this makes it so my AP does not pass out IPs that the router is; conversely my router is not passing out anything over .101

ip dhcp pool VMs

network 192.168.100.0 255.255.255.0

default-router 192.168.1.1

lease 10

exit

ip dhcp global-options 

 dns-server 8.8.8.8     # if you like using Google as your DNS server instead of your ISP- otherwise set as your gateway/router

I hope this helps out anyone else trying to set this up!

-Hix