Lab 7: Configure DHCP, NAT, and NTP

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Lab 7: Configure DHCP, NAT, and NTP

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Lesson format8 sections1 code block1 practice itemUpdated Oct 2, 2026

Take the three-router topology and add a simulated ISP connection. Configure DHCP on R1 to serve the LAN with proper options. Configure PAT on R1's WAN interface so LAN clients can reach the simulated internet. Add NTP so all devices have consistent time. This is the standard SOHO router configuration — every small business has something similar.

#Configuration on R1#link

bash

! DHCP server
R1(config)# ip dhcp excluded-address 10.10.10.1 10.10.10.10
R1(config)# ip dhcp pool LAN
R1(dhcp-config)# network 10.10.10.0 255.255.255.0
R1(dhcp-config)# default-router 10.10.10.1
R1(dhcp-config)# dns-server 8.8.8.8 8.8.4.4
R1(dhcp-config)# lease 1
R1(dhcp-config)# exit

! NAT inside/outside
R1(config)# interface gi0/1
R1(config-if)# ip nat inside
R1(config-if)# exit
R1(config)# interface gi0/0
R1(config-if)# ip nat outside
R1(config-if)# exit

! PAT ACL and configuration
R1(config)# access-list 10 permit 10.10.10.0 0.0.0.255
R1(config)# ip nat inside source list 10 interface gi0/0 overload

! NTP
R1(config)# ntp server pool.ntp.org
R1(config)# ntp source gi0/0

! Save
R1# write memory

#Verification#link

Configure DHCP, NAT, and NTP on R1. Verify DHCP leases with `show ip dhcp binding`. Verify NAT translations with `show ip nat translations` after generating traffic from a LAN host. Verify NTP with `show ntp status` — should say synchronized (may take a few minutes).

★ 20 XPmedium

exercise BLOCK (★ 20 XP)

A LAN client has an IP from DHCP but can't reach the internet. `show ip nat translations` is empty. What's the most likely cause?

Select your proof vectors above

#Common Mistakes#link

▪Forgetting `ip nat inside` and `ip nat outside` — NAT silently doesn't work
▪Excluding addresses only for R1's loopback but not the DHCP pool range — DHCP leases the gateway
▪Using `ip nat inside source` without `overload` — creates dynamic NAT (one-to-one), not PAT
▪NTP server unreachable — check UDP 123 isn't blocked

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Configuration on R1 Verification Common Mistakes

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October 2, 2026

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Laboratory sanity code

Isolate active probes on matched virtual networks and keep execution streams sandboxed.

! DHCP server

R1(config)# ip dhcp excluded-address 10.10.10.1 10.10.10.10

R1(config)# ip dhcp pool LAN

R1(dhcp-config)# network 10.10.10.0 255.255.255.0

R1(dhcp-config)# default-router 10.10.10.1

R1(dhcp-config)# dns-server 8.8.8.8 8.8.4.4

R1(dhcp-config)# lease 1

R1(dhcp-config)# exit

! NAT inside/outside

R1(config)# interface gi0/1

R1(config-if)# ip nat inside

R1(config-if)# exit

R1(config)# interface gi0/0

R1(config-if)# ip nat outside

R1(config-if)# exit

! PAT ACL and configuration

R1(config)# access-list 10 permit 10.10.10.0 0.0.0.255

R1(config)# ip nat inside source list 10 interface gi0/0 overload

! NTP

R1(config)# ntp server pool.ntp.org

R1(config)# ntp source gi0/0

! Save

R1# write memory