Why is arp -a showing so many incomplete addresses? When I execute the arp -a command I get a whole lot of incomplete entries and I don't understand why. Can someone please shed some light on this? I've not posted every single incomplete entry just because there are so many of them.

deza@PandaMacPro:~/home$ arp -a
(169.254.115.104) at (incomplete) on en0 [ethernet]
(169.254.143.2) at (incomplete) on en0 [ethernet]
(169.254.162.244) at (incomplete) on en0 [ethernet]
(169.254.216.162) at (incomplete) on en0 [ethernet]
(169.254.232.210) at (incomplete) on en0 [ethernet]  
(169.254.236.58) at (incomplete) on en0 [ethernet]
(192.168.1.0) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
(192.168.1.1) at a0:21:b7:ba:b7:b5 on en0 ifscope [ethernet]
(192.168.1.2) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.11) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.12) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.13) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.19) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.28) at (incomplete) on en0 ifscope [ethernet]
(192.168.1.254) at (incomplete) on en0 ifscope [ethernet]
(224.0.0.251) at 1:0:5e:0:0:fb on en0 ifscope permanent [ethernet]
(239.255.255.250) at 1:0:5e:7f:ff:fa on en0 ifscope permanent [ethernet]
It's not an issue.

It just means that there is some node on your network that's sending traffic to a non-existant IP address.