Unusual behaviour of ping responses

Hi everyone!

Have a curious situation here, and I THINK I know why it's happening, but I just wanted to confirm. We are currently testing some new ACL's where I work, and we are getting some unusual responses to our test pings. When we attempt to ping a gateway (say 10.2.2.1) from a network (192.168.0.0/24), the ACL's work correctly. When we attempt to ping a network/broadcast address (/24, so 10.2.2.0, or 10.2.2.255) I BELIEVE the router is proxy arp'ing back, with the Interface closest to the source, so say 172.16.1.1 for example.

My question is why does the router respond with a proxy-arp when it's the network/broadcast address, any not any other address behind the network? Is it because it see's itself as 'owning' those addresses, or belonging to that subnet on those addresses?

Any further info on this would be greatly appreciated!

Steve