Certain hosts not (always) pingable

[Hans Nieser]

Hello list,

Earlier tonight I installed 5.4-RELEASE on a machine (fileserver) that has 
a "3Com 3c905C-TX Fast Etherlink XL" integrated on the motherboard. I am 
experiencing however a rather weird issue; after a while, I lose 
connectivity with certain hosts on my LAN.

When (right after boot) I start pinging some hosts on my LAN, all looks 
fine for the first few minutes, but the longer I wait, the more hosts 
become 'unpingable'. Doing "arp -d -a" immediately fixes the problem, then 
after a few minutes it starts all over again. Also, the order of which 
hosts become unpingable seems to be the same. (gateway, elmar, aphax are 
usually the first three.)

This problem occurs only on this specific machine and the fact that it 
does not occur with a linux live-cd has led me to suspect that this is 
something specific to FreeBSD. But just in-case, I have tried swapping 
around UTP cables and using different ports on my switch, with no luck.

My home network has the following layout:

2nd floor switch (8 port 100/10mbit switch):
- My desktop computer   aphax.nieser.local      192.168.1.10
- My fileserver	        fileserver.nieser.local 192.168.1.5
- Uplink to 1st floor switch

1st floor switch (4 port 100/10mbit switch):
- ADSL modem (NAT)      gateway.nieser.local    192.168.1.1
- Uplink to 1st floor hub

(1st floor switch is actually integrated into ADSL modem)

1st floor hub (8 port 100/10mbit hub):
- My server             royen.nieser.local      192.168.1.3
- Mom's computer        beneden.nieser.local    192.168.1.x (dhcp)
- Uplink to wifi-AP

wifi-AP:                wifi.nieser.local       192.168.1.2
- Bro's computer        elmar.nieser.local      192.168.1.11
- Laptop                aphax-laptop.nieser.l.. 192.168.1.x (dhcp)

Relevant dmesg/ifconfig output:

xl0: <3Com 3c905C-TX Fast Etherlink XL> port 0xb000-0xb07f mem 
0xfb000000-0xfb00007f irq 20 at device 0.0 on pci2
miibus0: <MII bus> on xl0
ukphy0: <Generic IEEE 802.3u media interface> on miibus0
ukphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
xl0: Ethernet address: 00:0a:48:0f:40:c7

xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
         options=9<RXCSUM,VLAN_MTU>
         inet 192.168.1.5 netmask 0xffffff00 broadcast 192.168.1.255
         inet6 fe80::20a:48ff:fe0f:40c7%xl0 prefixlen 64 scopeid 0x1
         ether 00:0a:48:0f:40:c7
         media: Ethernet autoselect (100baseTX <full-duplex>)
         status: active

I haven't been able to find anything on google about this, can anyone 
help? I could probably save myself the trouble by spending a few euros on 
a real NIC, but I just can't stand problems I can't get solved... maybe it 
really is some kind of bug in the xl driver.

If more info is needed, please let me know