DCHP Snooping and macOS clients with "DHCP with manual address"

[rogueresearch]

Hi all,

I'm wanting to enable DHCP snooping and it's mostly working. However, we have some macOS machines that are configured in their System Preferences > Network to use "Using DHCP with manual address".  When DHCP snooping is enabled on my Cisco switch, those machines don't receive the subnet mask, router, and DNS server information.  If I set them to plain "Using DHCP", they do.

Is there a setting I'm missing, or are those things irreconcilable? :)

Thanks,

Sean

[Reza Sharifi]

Hi,

Maybe I don't understand the question entirely but why would you want to set a device with "Using DHCP with manual address". The purpose of DHCP is to provide all that information dynamically and not manually (statically). 

HTH

[rogueresearch]

As you know, servers like to have static (as in, unchanging) IPs.  So using "DHCP with manual address" is a nice way to specify the IP statically (on the server itself), but still get the gateway and DNS dynamically.

I know I can map MAC->IP on the DHCP server (and I do that too).

[Deepak Kumar]

Hi, 

As I understood, You have only IP address and subnet mask assigned on the MAC system and try to get the Gateway and DNS address from the DHCP. 

I think the system is sending ARP request and there is no entry in DHCP database, so traffic dropped as per DHCP snooping rule. 

Please add the below commands in your configuration for DIA and IP verify:

ip arp inspection

ip verify source

Regards,

Deepak Kumar