Wednesday, 20 June 2012

Cisco ESXi Licences

As Cisco is pushing virtualisation with their Unified Communications applications & UCS servers, you'll come across Cisco licence certificates for VMware ESXi licences.
It used to be that you went to the VMware OEM portal for Cisco for Cisco to redeem the licence keys to get the actual ESXi licence. For this you'll need an account on the VMware website to able to log in & redeem the licences, which you then enter into vSphere.
Now Cisco have started shipping actual licence keys for ESXi, but only for certain part codes:
  • R-VMW-UC-FND5-K9
To redeem these you enter the key directly into vSphere.

Wednesday, 13 June 2012

Lightweight AP Controller Discovery

Cisco's lightweight Access Points (AP) support discovering the Wireless LAN Controller (WLC) management IP address via several methods, including:

DNS Resolution
The AP tries to resolve CISCO-LWAPP-CONTROLLER or CISCO-CAPWAP-CONTROLLER using the DNS server configured by DHCP. However you may not have DNS A records for these, especially in small deployments with no DNS server onsite.

DHCP Option 43
The AP uses IP addresses provisioned via DHCP option 43. This consists of a hexadecimal string starting with F1, the number of WLCs multiplied by 4 & the IP addresses of these WLCs in hex. For example one WLC with IP address

1 x 4 = 04 (must be padded to 2 hex digits if less) = 0A238005  (must be padded to 8 hex digits if less)
Resultant hex: F1040A238005

Adding a 2nd WLC with IP address would result in F1080A2380050A238006.

If the WLC is in the same broadcast domain & has Master Controller Mode enabled the AP can discover it by sending out broadcasts. This won't work in large deployments where APs are spread across multiple networks & is considered bad practice.

Over The Air Provisioning
The AP listens to Radio Resource Management (RRM) messages transmitted by neighbouring APs & learns the WLC IP address from these. However this is considered insecure & usually disabled.

You can connect a console cable to the AP & manually configure with the WLC's IP address using the lwapp ap controller ip address command. This only works on APs that haven't yet associated with a WLC, but is useful if you have an AP that's refusing to associate via the other methods.