![]() Temp IP addr: 0.0.0.0 for peer on Interface: FastEthernet0/1ĭHCP Lease server: 0.0.0. and this is a DHCP request packet after the client-id option has been attached to the ip address dhcp command. Lease: 600 secs, Renewal: 300 secs, Rebind: 525 secs Temp IP addr: 172.18.0.3 for peer on Interface: FastEthernet0/1ĭHCP Lease server: 172.18.0.1, state: 5 Renewing This is a sample default DHCP request packet: DHCP: SRequest attempt # 1 for entry: ![]() You can inspect the actual client ID in ASCII and hex with the debug dhcp detail. Fairly nice, in that even for dynamic IP addresses, the actual IP address assigned rarely changes unless you go offline for an extended period of time. The new client ID will be the MAC address of the specified interface (which can be different from the interface you're configuring). This is apparently done based on the client MAC address unless that IP was already taken from the pool when the client connects, the DHCP server will tend to re-issue the old IP. To make the router behave like a workstation, use the ip address dhcp client-id interface-name configuration command. ![]() ![]() Obviously, if your ISP checks your MAC address (and at least most cable operators do), you might have a problem. Instead of using the interface MAC address as the client ID (as most workstations do), the client ID is the string '-ifname' where the is the interface MAC address in ascii and the ifname is the short interface name. If you configure a Cisco router as a DHCP client, you'll notice that it uses weird client-id in its DHCP requests (assuming you care about client IDs on the DHCP server).
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