arp response fails

[bcs]

Hi,

I have 3 FreeBSD 10.2-RELEASE machines and all of them suffers of the 
following problem. They are not responding to ARP requests which causes 
network problem for me, other hosts can't access my FBSD machines on the 
LAN nor my FBSD hosts can see each other unless I add permanent arp entry.

[root at fbsd10 /]# arping my.host.hu
ARPING x.x.x.x
Timeout
Timeout
Timeout

Pinging a linux host is ok from my bsd host:
[root at cool /]# arping linux.host.hu
ARPING y.y.y.y
60 bytes from 00:15:17:ae:0c:44 (y.y.y.y): index=0 time=189.143 usec
60 bytes from 00:15:17:ae:0c:44 (y.y.y.y): index=1 time=335.541 usec
60 bytes from 00:15:17:ae:0c:44 (y.y.y.y): index=2 time=200.227 usec
^C

I use ipfw but "ipfw -q -f flush" didn't solve the issue. Here are my 
sysctl.conf:
security.bsd.see_other_uids=0
net.inet.tcp.recvspace=512000
net.route.netisr_maxqlen=2048
kern.ipc.nmbclusters=1310720
net.inet.tcp.sendbuf_max=16777216
net.inet.tcp.recvbuf_max=16777216
kern.ipc.soacceptqueue=32768
vm.v_free_min=19170

/boot/loader.conf:
ipfw_load="YES"
net.inet.ip.fw.default_to_accept=1
kern.maxusers=4096
accf_data_load="YES"
hw.em.rxd=4096

any idea how to enable arp response?

Thanks guys!

Cheers,
Csaba