Bug 14841

In RFC 1122, Requirements for Internet Hosts -- Communication Layers);
Chapter II, 2.3.3 (Ethernet and IEEE 802 Encpasulation) is written:

[...]
Every Internet host connected to a 10Mbps Ethernet cable;

- MUST be able to send and recieve packets using RFC-894
  encapsulation.
- SHOULD be able to recieve RFC-1042 packets intermixed
  with RFC-894 packets.
[...]

It seems that FreeBSD does not support snap encapsulation on
Ethernet. Of seven different OS's, only FreeBSD had problems
with setting the arp replies. It's not usual that if we ask
with type ether, the replay is type snap, but it can happen.

Fix: 

I'm still investigating the problem. Help is welcome.
It seems that ATM does only support snap encapsulation
for tcp, so it should also be possible to implement
on Ethernet.
How-To-Repeat: (using snap encapsulation on router as specified RFC-1042)

# tcpdump -s 1500 -v -v
snap arp arp reply ibmrouter is-at 0:60:92:10:6d:20 hardware #6

# arp -n -a
? (192.168.115.252) at incomplete [ethernet]


(using ether encapsulation on router as specified in RFC-894)

# tcpdump -s 1500 -v -v
arp reply ibmrouter is-at 0:60:92:10:6d:20 (0:60:92:10:6d:20)

# arp -n -a
? (192.168.115.252) at 0:60:92:10:6d:20 [ethernet]