eth0 conflict

AP-Research HostAP-Research at
Thu Dec 9 17:59:44 EST 2004

<quote who="capacity77 at">
> Hi there!
> Anyone has an idea why it happens that hostap works good only if I
> ifconfig eth0 down?
What specifically doesn't work with HostAP?

> If i don't do it, the dhcp server gives the IP but then it's not even able
> to ping.
Who can't ping?  If it's the dhcp client then you may not be supplying
router information.
What can't you ping, an IP address or a DNS name?

> And if I do /etc/init.d/dhcp[d] restart when eth0 is still up, I get the
> error message
> Starting DHCP server: dhcpd failed to start - check syslog for diagnostics
How is this a HostAP issue?

> dhcpd: Multiple interfaces match the same subnet: wifi0 wlan0
> dhcpd: Multiple interfaces match the same shared network: wifi0 wlan0
You haven't told dhcpd which devices to use so it's trying to use ALL
configured devices.

> dhcpd: wifi0: unknown hardware address type 801
This is a virtual device which shouldn't be used for serving dhcp addresses.

> dhcpd: No subnet declaration for eth0 (
> dhcpd: Please write a subnet declaration in your dhcpd.conf file for the
> dhcpd: network segment to which interface eth0 is attached.
> dhcpd: exiting.
This should be self-explanatory.  Write a subnet declaration for eth0.

> kernel: wifi0: 00:09:5b:ba:16:13 auth_cb - alg=0 trans#=2 status=0 - STA
> kernel: wifi0: 00:09:5b:ba:16:13 assoc_cb - STA associated
In the absence of more debug information I'd say HostAP worked.

This isn't a HostAP issue.  It's a dhcpd configuration issue.

Since you didn't specify which flavor of Linux you're running I'll assume
it's RedHat.  Furthermore, since you didn't specify what you were trying
to accomplish, I'll assume you wanted to serve, using dhcpd, an address
pool on wlan0.  The simple answer to this dilemma is to add
"DHCPDARGS=wlan0" to /etc/sysconfig/dhcpd.  The complete answer to this
issue is to consult your dhcp server documentation.

KC Ferguson CIO/CTO
eXtreme Response Mobile HotSpot

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