Member Avatar for Mike!23

I am very new to Networking. When I was learning on, and configuring, a router as DHCP for practice...I stumbled over which ip address should I choose amongst many ! So, could someone clarify this confusion of differenciating addresses in general, (be it ip or else) ?

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Routers commonly carry several different kinds of IP addresses and each has a distinct role: a public/WAN address (your ISP-facing address), one or more LAN/gateway addresses (the router’s address inside each local subnet), DHCP pool addresses assigned to clients, static addresses reserved for servers or management, and logical/virtual addresses used for HA (HSRP/VRRP) or loopback interfaces. There are also transient addresses created by NAT translations when internal hosts talk to the Internet.

To tell them apart look at how the address is assigned and where it lives:

  • Check the router’s interface list (web UI or CLI) to see which IP is bound to which physical or virtual interface and what subnet/mask it uses.
  • Inspect the DHCP lease table to see dynamically assigned client IPs and the lease expiry.
  • Use the ARP/cache and NAT translation tables to map IP ↔ MAC and external ↔ internal addresses.
  • Read routing and firewall rules to see which IPs are used for gateway, management, or services.

Practical notes tied to earlier replies: is correct that a MAC is a better device identifier than a transient DHCP address, but remember modern clients can randomize or spoof MACs. ’s point about DHCP pools being ephemeral is also key—use DHCP reservations (bind an IP to a MAC) or give servers static IPs when you need stable addressing. For policy or segmentation, prefer interfaces/VLANs and subnets (and firewall rules per interface) rather than relying on single host IPs.

Quick useful commands (examples only — exact syntax varies by device):

# Linux/macOS
ip addr show
arp -n

# Windows
ipconfig /all
arp -a

# Common router/IOS checks
show ip interface brief
show ip dhcp binding
show ip nat translations

Caveat: document an IP plan (subnets, purpose, reserved ranges) so the purpose of each address is obvious later.

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Member Avatar for rproffitt

Too vague a question. But let's try this. Forget the IP for a moment and if you want to know the unique PC or device, look up it's MAC address which for most setups is static.

Now if some newbie IT staff thinks this is a solid solution to tracking a PC or device I turn on MAC randomization and see them lose the rest of their hair.

-> Again, what are you trying to measure or find out?

Member Avatar for DGPickett

DHCP operates a pool of IPs for clients that need them. Usage is a bit worthless unless they stay assigned a long time. As noted, the mac from the ethernet layer is a better id.

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