I know I said in my last blog post that I’d be discussing the OSI layer, but I left my documentation at work and I received a nice package in the mail yesterday: an AIR-LAP1142N-EK9.
It’s a fully capable 802.11n access point, both 2.4 Ghz and 5 Ghz capable, powered by either an external adapter or PoE. It came without adapter and with Lightweight Access Point (LAP) IOS on board, hence I got it rather cheap. Of course, I don’t have a Wireless LAN Controller (WLC) lying around that can configure a LAP. So I had to convert the IOS image to one of a standalone AP.
That proved difficult at first. The 1142N does have a console port, but after booting up it starts searching for a WLC and gets stuck in a loop: DHCP, searching WLC? releasing IP, DHCP, searching WLC,… So console access was not possible. On top of that, it didn’t reply to ARP requests, except for those originating from the subnet gateway (I suspect this is a security feature).
But, just as with Cisco switches, the 1142N LAP has a mode button, and if you hold it while it powers up, it will not load in any configuration or IOS but instead will fallback to IP 10.0.0.1/24 and query for a TFTP server, requesting a file named ‘c1140-k9w7-tar.default’ It does this by sending out broadcasts. I’ve set up a TFTP server in the same subnet (e.g. 10.0.0.10/24) and indeed it reacted… But nothing happened: still ARP information missing. So, after creating a static ARP entry of the 1142N on the TFTP server, TFTP started working! The 1142N retrieved the IOS, and after rebooting it showed as ‘LAP-1142N-EK9 running AP-1142N-E-K9 IOS’. It requested an IP address by DHCP again, after which it was accessible by telnet. Default username and password: Cisco/Cisco. After gaining telnet access, most things were similar to any other Cisco device: SSH key generation, line vty, interfaces,… After configuring it, it didn’t disappoint: throughput was around 95 Mbps, while it was connected on a 100 Mbps PoE switch, and at 20 meters and three walls, still 80 Mbps!
Reggle 
toys toys toys !! 😉
I have the same model could you guide me on how to configure it on standalone mode? If you do have a step by step guide i would really appreciate it
Well, you first need to get hold of a standalone IOS version. The rest is explained in the article I wrote. A few more details:
– I used a lot of wireshark to examine what the LAP does when booting.
– If it’s still in LAP mode, try to boot it up while holding the mode button on the model (bottom side), it will boot with default configuration and eventually start broadcasting for TFTP.
– Source IP will be 10.0.0.1 so take something in the same /24 subnet as your TFTP server.
– Since it’s a broadcast and the LAP doesn’t seem to ARP at that moment, you’ll manually have to make an ARP entry for the LAP on the TFTP server.
– Once you’ve done that, a file transfer should start. You may have to rename the IOS file.
– You can see the source MAC needed for the ARP entry, as well as the name of the file the LAP is needing in Wireshark.
– After that, reboot.