Intel 4965 to Prism based AP Problems

On Thu, 7 Feb 2008 15:46:51 -0500, BostonDriver wrote in :

Run a traceroute (tracert in WindowsSpeak) across the wireless link to see if you're experiencing packet loss and where it might be occurring.

Traceroute to my AP (FreeBSD box) showed NO drops.

I did run ping the entire time (-n 10000000) I experienced the problem and dropped just 1 or 2 datagrams. A few had larger delays (in ms still), but still worked. I'm using the default timeout with XP.

While I saw the problem, I was ssh'ed into another system on the 'net as well as my AP (FreeBSD system). Both were quite responsive.

------------------------------------------------------------------------ View this thread:

On Fri, 8 Feb 2008 11:10:50 -0500, BostonDriver wrote in :

Traceroute to the remote site on the Internet. Post the exact output here.

C:\\>tracert -d

Tracing route to

[198.65.131.42] over a maximum of 30 hops:

1 3 ms 1 ms 1 ms 172.16.6.1 2 * * * Request timed out. 3 * * * Request timed out. 4 * * * Request timed out. 5 * * * Request timed out. 6 * * * Request timed out. 7 * * * Request timed out. 8 * * * Request timed out. 9 * * * Request timed out. 10 * * * Request timed out. 11 * * * Request timed out. 12 * * * Request timed out. 13 * * * Request timed out. 14 * * * Request timed out. 15 * * * Request timed out. 16 * * * Request timed out. 17 * * * Request timed out. 18 * * * Request timed out. 19 ^C C:\\>

------------------------------------------------------------------------ View this thread:

BostonDriver hath wroth:

Let me guess. You have a PPPoE DSL internet connection and your neighbor with the open access point has a cable modem? Checking

66.129.232.2 ... Groan. You're posting from work at Juniper? Oh well.

My guess(tm) is that the difference is that PPPoE needs a slightly smaller MTU. Try setting the MaxMTU on your new laptop to 1492 instead of the usual 1500.

See explanation at 14.25:

On your FreeBSD box, try: ping -s 1472 -D your_ISP_gateway_IP_address or ping -s 1472 -M your_ISP_gateway_IP_address

1472 is actually a 1500 byte header due to the 28 byte header. (20 for the header and 8 for the PPPoE). If you're running PPPoE on your DSL connection it should fail. Note that you're pinging your ISP, not your local router. Now, decrease the MTU size to 1492 - 28 = 1464 and try again. If my guess(tm) is correct, the 1472 will drop packets, while the 1464 will work.

If you can find a Windoze box, you migth also try MTUroute.exe v2.1:

If you can't find the Linux version or Windoze box, try the web based version at:

On Sat, 9 Feb 2008 13:14:57 -0500, BostonDriver wrote in :

What does a tracert to someplace you can get look like?

If it looks normal, then this would seem to be a routing problem. Perhaps there is some blocking in place?

Traceroute isn't the best guide, as everything I tried (yet can get to) show similar results (due to firewalls along the way), both wireless and wired.

With the RJ45 plugged in, there are no problems to any destination. Swap RJ45 with wireless for the last segment, I hit the problem I described initially. I power up the old laptop (802.11b only), no problems to anywhere.

In this case, all wireless cards are Netgate, 2511CD PLUS EXT2. Only with the new laptop (and the Intel 4965 miniPCI a/b/g/n card) talking to my FreeBSD AP is there an issue. That, or these 2511CD Plus ext2 cards don't like talking to anything but themselves. Friends with new Dells (similar, if not the same Intel wireless clients) all have the same issue.

------------------------------------------------------------------------ View this thread:

Here is the card I use in HostAP mode on FreeBSD 4.10-Stable:

'Netgate'

I have several of these setups, all in Soekris boxes except one, which is a FreeBSD desktop used in cases such as this to debug problems (wireless or otherwise).

All machines used as AP exhibit the same problem. Any time a wireless client that isn't one of these 200mW 2511 CD PLUS EXT2 (either cardbus or miniPCI) the problem exists. Other 802.11b only clients (Orinoco) which I've tried in the past do work just fine.

------------------------------------------------------------------------ View this thread:

BostonDriver hath wroth:

Did your news server miss my reply to your problem? See:

No, your guess is wrong. I have a cable modem. No PPPoE here.

tcpdump on the FreeBSD AP (on the uplink to Comcast) shows no difference in MTU/TCP segment size when things work and when they do not work. Using the old laptop (802.11b) shows same packet sizes as when using the new laptop and a wired connection. Likewise, what little traffic that makes it using the new laptop (802.11a/b/g card) has the same MTU as well. There is no fragmentation going on. All TCP segments show DF.

I bought an AP, plugged its "ISP" port into the FreeBSD switch. New laptop works fine. (Traffic dumps are same as above).

So, the topology is fine. There is something about this new wireless card and that card in the FreeBSD looks like the problem.