We have a customer who have used a 'class-b' '/16' subnet mask on one of their Firewall interfaces. One of the interface addresses that they have then used is 172.x.x.255. Is this in any way a legal address? In theory it isn't the broadcast address, which would have 255 in the last two octets, but I'm not convinced that you can use 255 at all? And they are getting some strange traffic that's showing up on the standby firewall of their HA Pair, so I was just wondering if this might be the reason?
The 255 in the last octet doesn't mean that it is the Broadcast address. If you have 172.16.0.0/16 Broadcast address is 172.16.255.255. But you Can use the IP 172.16.1.255 has a host. It depends on the Net Mask. This example:
Hosts: 172.16.100.1 to 30
I hope this helps you