I already had a WRT54G ver. 1 running as a node -- only problem is that one of the micro coax antenna cables pulled out of the connector. I then picked up a WRT54GS (ver. 1; Serial No. starts with CGN1) and installed bbhn-1.0.0-wrt54gs.bin. Everything was fine until I tried switching it from a node to an access point: I changed the mode and saved the setting and rebooted without first changing the IP address as well. Now I can see its SSID with a WiFi scanner, but I cannot get into the configuration page or even discover what IP it's using: it's connected to the ethernet port of a Windows 7 laptop, but neither

arp -a

nor a ping scanner on the whole 172.x.x.x range finds anything, so I don't know what IP address I would have to use to upload the firmware again using tftp.

I've tried both the regular reset and the 30-30-30 reset to no avail.

Am I going to have to use JTAG on this thing?

Question has already been asked many times on the forum before. You can also find your answer on the website. Please check FAQ --> Network FAQs --> I changed my unit to mesh AP and I can't get back in

or

User Documentation --> How to use the web interface --> Mesh Access Point considerations

Thanks for that information. I had searched for the word "brick" without finding what I needed.

However, I still did not find the solution to my problems. I still am unable to access the WRT54GS that is now an access point -- not by connecting to it directly at 172.27.0.100 and not by connecting it by ethernet cable to the router that is operating as a mesh node then pointing the browser to 172.27.0.2:8080. In fact even the one that is a mesh node is accessible not at 172.27.0.1:8080 but at 10.110.144.121:8080 (and I am sure that I did not change it to that); the one that is now an access point is not accessible at 10.110.144.122:8080 when connected by ethernet cable to the other one either: in fact

arp -a

shows 10.110.144.122 as the address of the laptop's Ethernet interface and shows nothing with a MAC address corresponding to that of the access point.

A further problem is that the WiFi scanner sees the access point on Channel 6 rather than on Channel 1. I did not change it from whatever the bhnn firmware set it to: the only things I changed were the SSID and then, when it was working OK as a mesh node, I changed it to an access point without changing anything else -- not even the IP address.

Have you tried plugging the two nodes together via an Ethernet cable, and either connecting via wireless or a hard Ethernet cable connection to the AP, and navigating to http://172.27.0.2:8080/ ?

Try setting the ip of the computer manually.

the old 2 node trick is no longer valid because the AP now gives 10.x address unless you put in NAT mode.

Try this...(I just thought of this)
Go into failsafe mode (we divert after we type "mount_root") on the "not-quite-bricked" router, and in the /etc/nvram file, change/add a line that reads "config=MESH". Next, copy and paste the contents of the /etc/config.mesh/ folder over to the /etc/config/ folder (overwriting everything). Then, reboot.

If that fails to work, the only other option I can think of is to tftp the firmware back to the router.

You could try using Wireshark to capture the ip when the node boots up.  I have used this on many routers that I do not know the IP, or failed to write down when I configured for some test.  Just direct connect to it and fire up the software on the correct interface and the unit should announce it's IP shortly after you apply power.