WLAN Controller learning IP/MAC on wrong virtual interface

[patoberli]

Hello

I believe since I upgraded my WiSM to 7.0.250.0 is it learning a MAC address on the wrong virtual interface.

The setup:

- a Linux server with 2 virtual interfaces, both use the same MAC address, one is the gateway of VLAN 116 and one is the gateway of VLAN 240

- a WiSM with several virtual interfaces, including one in 116 and one in 240

Here the arp table with the problem:

    MAC Address        IP Address     Port   VLAN   Type
------------------- ---------------- ------ ------ ------

00:50:56:BD:32:92   172.16.240.9     29     240    Host
00:1E:4A:FA:87:8B   172.16.102.12    29     0      Permanent
00:1E:4A:FA:50:0B   172.16.102.13    29     0      Permanent
00:1E:4A:FA:81:2B   172.16.102.14    29     0      Permanent
00:50:56:BD:32:92   172.16.116.9     29     240    Host
00:1D:E0:31:55:23   172.16.116.185   29     116    Client
58:94:6B:68:50:E8   172.16.118.201   29     116    Client
1C:B0:94:B7:38:08   172.16.118.234   29     116    Client

And here after I made a PING from the controller to the listed ip address:

    MAC Address        IP Address     Port   VLAN   Type
------------------- ---------------- ------ ------ ------

00:50:56:BD:32:92   172.16.240.9     29     240    Host
00:1E:4A:FA:87:8B   172.16.102.12    29     0      Permanent
00:1E:4A:FA:50:0B   172.16.102.13    29     0      Permanent
00:1E:4A:FA:81:2B   172.16.102.14    29     0      Permanent
00:50:56:BD:32:92   172.16.116.9     29     116    Host
00:1D:E0:31:55:23   172.16.116.185   29     116    Client
38:E7:D8:D3:7C:FA   172.16.118.92    29     116    Client
58:94:6B:68:50:E8   172.16.118.201   29     116    Client
1C:B0:94:B7:38:08   172.16.118.234   29     116    Client
18:AF:61:12:E9:FB   192.168.1.59     29     117    Client

Has anybody else the same problem?

The host 172.16.116.9 is also the configured DHCP server on VLAN 116.

Is there a way to statically configure this IP address on that VLAN? Because it causes every few days a service outage on that VLAN (which is bound to an SSID).

[Stephen Rodriguez]

Per the best practices, you should not have a server that the clients need to use on an interface the WLC is aware of.

[patoberli]

Are you sure that is also valid for the normal virtual interfaces?

So you say it's forbidden by the guide to have communication between two wireless clients in the same SSID?

In this example it's the DHCP server which is in the same VLAN as the clients. This server is also the gateway of that VLAN.

[Stephen Rodriguez]

Yup, I'd say still valid. Seeing as it is the gateway, if it had different mac addresses per interface, it might still work.

No, clients in the same subnet can communicate, but it is not recommended to 'bridge' wired and wireless with a WLC. The WLC doesn't like to bridge the communication by default, though there are work arounds.

 I might also say that as it uses the same MAC address for both virtual interfaces L2 is going to be messed up as each time there were an ARP the entry would change.

Take a look and see if you can manually change the mac for one of the interfaces and test again.

HTH,

Steve

[patoberli]

Just discovered that it's near impossible to have a different MAC address on a VLAN interface on Linux. I'm currently checking if I can add an additional interface to that server. At least I think I know now where the issue is coming from.

Out of curiosity, how does that work with a Cisco router? I mean they also have the same MAC Address on every VLAN Interface. In this setup the Cisco router wouldn't be allowed to be a DHCP server for the different WLANs terminated on the WLC?