VLAN ARP problem

Hi,

on a linux box I set up an 802.1q VLAN eth0.11 and at the other end of
the cable I configured a Cisco Aironet access point to use VLAN 11,
too.

So I have:
Host <--- air ---> AP <--- Tagged Ethernet ---> Linux

When I try to make a connection from the host to the linux box I see on
the Linux box:

18:33:08.476364 arp who-has 192.168.1.99 tell 192.168.1.7
18:33:10.476544 arp who-has 192.168.1.99 tell 192.168.1.7
18:33:12.477419 arp who-has 192.168.1.99 tell 192.168.1.7
18:33:16.477788 arp who-has 192.168.1.99 tell 192.168.1.7

Where 192.168.1.7 is the IP of the host and 192.168.1.99 is the IP of
eth0.11.

I set /proc/sys/net/ipv4/eth0.11/prox_arp to 1 and, because that didn't
help, also /proc/sys/net/ipv4/eth0/prox_arp.

Why doesn't the linux box answer the arp requests?

Best regards,
André