Cards seeming connect but unable to route traffic?

Denis Vlasenko vda at
Fri May 7 11:51:16 EDT 2004

On Friday 07 May 2004 06:12, Drew Dowling wrote:
> Hash: SHA1
> > Can you be more precise? I'll define "precise" by example
> > how I'll describe packets on my (wired) network:
> >
> > -- BEGIN EXAMPLE ---
> [snip]
> > -- END EXAMPLE ---
> >
> > In other words, I don't try to describe what I see.
> > I am actually showing others everything I see.
> Certianly; espically for one who graciously offers help.
> On host (hostAP_wlan0)
> # ifconfig
> lo        Link encap:Local Loopback
>           inet addr:  Mask:
>           inet6 addr: ::1/128 Scope:Host
>           UP LOOPBACK RUNNING  MTU:16436  Metric:1
>           RX packets:36 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:6168 (6.0 Kb)  TX bytes:6168 (6.0 Kb)
> wlan0     Link encap:Ethernet  HWaddr XX:XX:XX:XX:XX:XX
>           inet addr:  Bcast:  Mask:
>           inet6 addr: xxxx::xxx:xxxx:xxxx:xxxx/64 Scope:Link
>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:27670 errors:0 dropped:36 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:0 (0.0 b)  TX bytes:3137303 (2.9 Mb)
>           Interrupt:11 Memory:d0b18000-d0b19000

Try without ip6, just to rule out remote possibility that ip6 enabled
kernel have some bug.

> # tcpdump -nlei wlan0 -s0 -vvv icmp or arp
> tcpdump: listening on wlan0
> 0 packets received by filter
> 0 packets dropped by kernel
> # tcpdump --help
> tcpdump version 3.7.2
> libpcap version 0.7.2

Tcpdump sees nothing.
Try to switch wlan0 into monitor mode and tcpdump it again.
802.11b has quite a number of special packets not normally seen.
(tcpdump 3.7 has incomplete support for 802.11, get 3.8)

Ideally, you should do sniffing in monitor mode with
another computer, if you have one.

> On host (XP client) I have ethereal running and I see the APR
> packets increment.  I havn't yet discovered a good way to dump text (only
> had it < 24 hours).

The point is, we still don't know whether they actually make it to the

> When I select the captured packets there are three boxes to look.  The
> one named 'Address Resolution Protocol (request)' shows amoung other
> things the source and targets IP and MAC.  The IPs are the ones for each
> repective box.  The MAC of the source is correct.  The MAC of the target
> is blank (or all 0s).

MAC cannot be ever 'blank', it's a 6 byte field in the packet,
always present. 00:00:00:00:00:00 is not ok too, should be
ff:ff:ff:ff:ff:ff for bcast frame. Strange.

Maybe install Linux on this box (a small toy install) and try to get
it working in Linux first.

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