In article , LWG wrote: :I was using a hotel network and was curious about what was out there so I :brought up ethereal. I started a capture and could not see any traffic. I :was just curious about why? Is there something different about the way they :have built there network?
Possibly yes. There are some routers available that listen for ARP packets on interfaces, and reply back as if they were the target address (on the assumption that the first thing arp'd for would be the gateway IP of the network the user's equipment is set up for. In this way, no matter what gateway address the user's equipment is set up for, the user gets connected without having to reconfigure.
These routers can handle multiple ports with the same IP address -- they use distinct internal IP addresses per port and do NAT at the port level.
All of this relies upon separation of segments -- otherwise the user in room 10B who happens to be using IP gateway 192.168.0.1 could end up with their traffic mixed with the user of room 28C who also happens to be using an IP gateway of 192.168.0.1 . Thus, this equipment would take extra care to be sure the ports were not talking to each other.
But the answer could be a lot more simple than that: they could just use a regular switch (say a Cisco 3550) with the port protection facility turned on to prevent traffic from flowing between ports. Or they could put every room into a different VLAN and put on an ACL that blocks ARP and other broadcast packets from flowing between ports. Recall that if you are using switched segments, then the only traffic you will see on your segment is traffic that you generate, or that is destined to you, or which is sent to a broadcast or multicast MAC and the switch thinks that maybe your segment might happen to have a suitable destination. Block those broadcast packets and you block everything except local traffic.