ath using hostap sets MTU to 2290 / channel '0' no longer works

Nenhum_de_Nos matheus at
Wed Jul 30 12:32:55 UTC 2008

On Wed, July 30, 2008 00:32, Chris Buechler wrote:
> Sam Leffler wrote:
>> John T. Yocum wrote:
>>> Hello,
>>> I have a system running pfSense, which is built on top of FreeBSD
>>> 7.0-RELEASE-p3. In the system I have an Atheros wireless card, which
>>> when I enable hostap, changes it's MTU to 2290. If an explanation is
>>> listed on a man page, I apologize, I did try searching.
>>> Any ideas why this might happen? It doesn't appear to be a pfSense
>>> issue, as it appears their code actually tries to set the MTU to 1500.
>>> Only reason I ask here, is I noticed in my searching on Google, I
>>> noticed others that aren't running pfSense have their MTU set to 2290.
>> MTU on an 802.11 network is 2290.  If you don't want the default then
>> change it.  If you cannot then please provide the exact steps you take
>> that do not work.
> Thanks for the reply, Sam!
> I have an ath card I'm working with that sets its MTU to 1500 in hostap,
> so there seems to be inconsistent behavior here. This card, specifically:
> We added a forced MTU of 1500 to wireless cards in pfSense (as a stop
> gap testing measure since they're frequently bridged to Ethernet and the
> bridge won't work unless the wireless card is 1500), but it still
> appears to revert to 2290 for people.
> I haven't had time to fully quantify this, and I can't replicate it with
> the hardware I have at hand as it uses 1500 without specifying any MTU.
> If I can come up with better info and steps to replicate, I'll post back.
> While I have your attention, we have found one change in behavior
> between 6.x and 7.0. I'm not sure if it's a regression or intentional,
> any insight would be appreciated. "ifconfig ath0 channel '0'" used to
> work in 6.x with hostap mode. Now users are finding their AP does not
> show up unless they manually specify a channel. Running that command
> shows:
> # ifconfig ath0 channel '0'
> ifconfig: unknown/undefined channel number 0 flags 0x0
> At boot time when the above is set, I get (dmesg|grep ath0):
> Jul 27 18:24:44 pfSense kernel: ath_hal: (AR5210, AR5211,
> AR5212, RF5111, RF5112, RF2413, RF5413)
> Jul 27 18:24:44 pfSense kernel: ath0: <Atheros 5212> mem
> 0x88010000-0x8801ffff irq 10 at device 0.0 on cardbus1
> Jul 27 18:24:44 pfSense kernel: ath0: [ITHREAD]
> Jul 27 18:24:44 pfSense kernel: ath0: using obsoleted if_watchdog
> interface
> Jul 27 18:24:44 pfSense kernel: ath0: Ethernet address: 00:0b:6b:20:3a:4d
> Jul 27 18:24:44 pfSense kernel: ath0: mac 5.9 phy 4.3 radio 3.6
> Jul 27 18:24:47 pfSense kernel: ath0: ath_chan_set: unable to reset
> channel 6 (2437 Mhz, flags 0x490 hal flags 0x150)
> Jul 27 18:24:47 pfSense kernel: ath0: unable to reset hardware; hal status
> 0
> The above was also seen by a pfSense user with a different ath card,
> miniPCI I believe. Numerous people have reported that "auto" channel
> (what our GUI translates to channel 0 in ifconfig) no longer works with
> ath cards on 7.0-based versions when they were working fine previously
> on 6.2 and 6.3-based versions.
> The ifconfig man page mentions using channel - or any should do the same
> as 0. Both of those do not produce any error messages (they return no
> output), but the AP still isn't visible. I haven't confirmed this part,
> but I believe running ifconfig ath0 down / ifconfig ath0 up after
> running either channel - or channel 'any' will make it work. Not sure on
> behavior at boot time.
> I tested an old wi(4) card with channel '0' and it still works the same
> as in 6.x.
> I was waiting to post until I had time to gather more definitive
> information but since someone else brought it up, thought I'd add to it.
> If I can help gather any additional information please let me know.
> thanks,
> Chris
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[matheus at xxx /usr/home/matheus]$ dmesg | grep ath0
ath0: <Atheros 5212> mem 0xec1f0000-0xec1fffff irq 16 at device 8.0 on pci0
ath0: [ITHREAD]
ath0: using obsoleted if_watchdog interface
ath0: Ethernet address: xx:xx:xx:xx:xx:xx
ath0: mac 7.9 phy 4.5 radio 5.6
[matheus at xxx /usr/home/matheus]$

and I need to make it use 1500, this is set on

/sbin/ifconfig ath0 mtu 1500 mediaopt hostap

what I have in this box is:

interrupt storm detected on "irq16:"; throttling interrupt source

on the atheros card irq. every single reboot :(

sometimes when heavily used the wlan dies, usually the atheros based
freebsd-7 notebook kills this ap. need a hostapd restart to go back to


We will call you cygnus,
The God of balance you shall be

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