trust device with static ip ?

[levitan.eli]

Hey there !

I'm a new intern in a networking team in a big organization and I need your help figuring something I dont get...

A member of our team had to plug an old Time-clock to the network, and it has a static ip-address.

So I pinged the address of the clock and it was unreachable until he configured the SW to trust the port where the Time-clock was connected.

Now my questions are:
1. Why did he had to trust the port ? Is it because it has a static ip address ?

2. Was it a "ip dhcp snooping trust" command / "ip arp inspection trust" command ?

I know I can just ask him but I've already asked twice and got confused every time with other stuff...

Thanks

[MHM Cisco World]

trust vs Untrust is different in dhcp message that can allow to pass through.

if you config port as trust that only allow dhcp offer, ack, nak. i.e.  only message that send  from DHCP server not client.

ip arp inspection is security for SW, where if client connect to port and it get ip from dhcp, this ip is store in SW with this port, now when this client what to connect other client is send ARP, SW check Mac and IP in ARP and see if it correct after match to store table or not, if yes the arp is allow to flow if not the arp is drop.