DHCP Exclusions: Reserved Statics on a Single LAN

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Configure an IOS-XE router as a DHCP server with a correctly scoped pool and an excluded-address range that protects the gateway and a reserved static server (.10). Two Alpine clients obtain addresses dynamically from the remaining range (starting at .11). Verify leases, confirm the excluded count, and ensure the reserved static never appears as a DHCP binding.

Learning objectives

• Build a DHCP pool on an IOS-XE router with required options: network/mask, default-router, dns-server, domain-name, and lease.
• Implement an excluded-address range that reserves infrastructure and static server IPs from leasing.
• Operate Alpine Linux clients as DHCP clients (udhcpc) and verify they lease addresses within the allowed range.
• Validate router DHCP state with show commands: pool utilization, excluded count, and current bindings.
• Confirm end-to-end reachability from dynamic clients to both the gateway and a statically addressed server.

Troubleshooting focus

• Client fails to get an address due to missing DHCP pool or wrong network mask.
• Duplicate IP conflict caused by not excluding the reserved static server address.
• Incorrect default-router option prevents client from reaching off-host destinations.
• SW1 access port(s) down or mis-cabled so DISCOVER never reaches the router.
• Client not actually running a DHCP client (udhcpc) or link down at boot.