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We recently did a wireless integration for a client based on the Linksys Business Series SRW224P PoE switch, utilizing the WAP54GP as our access points. The SRW224P switch has been rock solid, although it has some quirks in features; port throttling for instance limits all ports on the LAN to a fraction of 100 Mbps when a single port is lower than a given arbitrary threshold. I chose the WAP54GP based on its support of PoE and some nice features like multi-SSID capability, roaming and IAPP, VLANs, etc. What I did not anticipate was a product (possibly too) early in its life cycle that does not seem to have been tested well enough by Linksys and a rebooting phenomenon that has been very hard to pin down. Some other arbitrary limits come on the WAP54GP too, such as a 32 wireless client limit!? The whole setup has worked pretty well, save for when it’s rebooting and at a very low cost; the client paid about $1,000 for a four AP system.

The rebooting issues began almost immediately upon installation. We noticed the issue and chalked it up to power issues at the client site, based on the fact that they are located in a 100+ year old building. At first, we suspected a PoE problem, but putting the APs on UPS batteries did not help the problem, so we started logging the access points via syslog. Mysteriously, the problem disappeared for about two weeks, until two days ago. It turns out that our tech on-site recently migrated a single user from the wired LAN back to wireless. As we examined the syslogs today trying to figure out what is going on, I noticed a trend that seems to point to the recently migrated user’s machine: the access point closest to that machine reboots first, then the next closest reboots, then the farthest AP sometimes reboots. The farthest AP does not always reboot, but this could be because the client machine reconnects to a stronger signal before reaching that AP. Looking at our logs, it became apparent that we moved that particular machine to the wired LAN at the same time the reboots stopped happening. With a small injection of logic, it is easy to see that the reboots are obviously being caused in chain reaction style because the client machine is hopping to the next closest access point when the first goes offline while rebooting.

At this point, we have not fully tested the client PC to see if it is causing the problem somehow or if the amount of data being transferred to and from it is the problem. I suspect that it is the latter as I read many reports of similar issues with other Linksys products and recall my own issues with my first wireless router, the notorious BEFW11S4. That platform was so buggy that Linksys ended up revising the entire chipset and I got a brand new revision 2 some time after my warranty expired.

So, we are at Level 2 with Linksys tech support and will hopefully figure this one out soon. At least I got to know a little more about the APs in the process:

WAP1 Linux version 2.4.21openrg-rmk1 #1566 Thu May 11 12:47:23 EDT 2006
WAP1 CPU: XScale-IXP4xx/IXC11xx revision 1
WAP1 Machine: Gemtek IXP425 WX5715
WAP1 Memory range 0xfff000-0×1000000 is excluded because of PCI DMA bug
WAP1 Kernel command line: console=ttyS1,115200 root=/dev/ram0 rw nohalt
WAP1 Memory: 16MB = 16MB total
WAP1 Memory: 12696KB available (892K code, 2354K data, 224K init)
WAP1 XScale Cache/TLB Locking Copyright(c) 2001 MontaVista Software, Inc.
WAP1 POSIX conformance testing by UNIFIX
WAP1 PCI: bus0: Fast back to back transfers disabled
WAP1 Linux NET4.0 for Linux 2.4
WAP1 Based upon Swansea University Computer Society NET3.039
WAP1 Initializing RT netlink socket
WAP1 Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled
WAP1 ttyS00 at 0xff000003 (irq = 15) is a XScale UART
WAP1 ttyS01 at 0xff001003 (irq = 13) is a XScale UART
WAP1 RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize
WAP1 loop: loaded (max 8 devices)
WAP1 NET4: Linux TCP/IP 1.0 for NET4.0
WAP1 NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
WAP1 802.1Q VLAN Support v1.8 Ben Greear
WAP1 All bugs added by David S. Miller

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