11-20-2019 10:09 AM
So when you create a DHCP reservation on your DHCP server and set any management interface to utilize DHCP, you are now reliant on DHCP being accessible at all times to manage your network devices without needing to physically access the device via the console port.
Think about it in this scenario:
Something on the network is preventing communication to your DHCP servers and the traffic is being reset. With this on-going issue the decision is made to reload one of these pieces of network gear you are relying on DHCP reservations to get the same address, but they can't actually pull an address because they can't talk to the DHCP servers. You now don't have a way to manage these devices remotely and need to access them physically via the console port.
In this situation a simple static address configuration would prevent any question about what will happen if you reload a piece of equipment. The static address will always be accessible and your networking equipment is in no way reliant on another piece of infrastructure being online to maintain full functionality.
Now if your co-workers are strict about the DHCP reservation being in place because they don't want to adjust the DHCP scopes, you simply change the reservation to an exclusion and static the information in on the device in question. The exclusion will tell the DHCP server to not hand out the address, but it will be notated on the DHCP server that an address is in use (because it's excluded from distribution).
If you have a device with a static assignment and you go ahead and create a DHCP reservation nothing adverse will happen, but someone looking at your DHCP server will think that the device is set to DHCP when it isn't and if they ever attempt to modify it's IP address by updating the reservation it could cause some confusion. An exclusion essentially tells anyone looking at the server that the client device isn't set for DHCP, while a reservation would tell me it is set for DHCP.
