UDP broadcast 255.255.255.255
 

Hi, I have the following question about networking. I sniff on one of my own machines to see if anything is sent out by any software which I am unknow with.
I find out that the following information:

IP Add src: 192.168.1.157
Dest IP: 255.255.255.255
Protocol: UDP
Port Src: 1167
Dest Port: 2798

Is it a broadcast since the dest ip is 255.255.255.255? From my understanding, broadcast 255.255.255.255 won't cross subnets, so only machines in the same subnet will receive this package. Am I right?

But I am see there is resposne from outside for this request. There is a ARP->response for this. What is ARP? Why they can receive this package?

I am using my LAN behind a Linksys router (Also support NAT) at home. Can some one tell me what dest IP 255.255.255.255 means?

Thanks