7.2.10 Packet Tracer - Configure DHCPv4 (Instructor Version)
Topology
7.2.10 Packet Tracer - Configure DHCPv4
Addressing Table
| Device | Interface | IPv4 Address | Subnet Mask | Default Gateway |
|---|---|---|---|---|
| R1 | G0/0 | 192.168.10.1 | 255.255.255.0 | N/A |
| S0/0/0 | 10.1.1.1 | 255.255.255.252 | N/A | |
| R2 | G0/0 | 192.168.20.1 | 255.255.255.0 | N/A |
| G0/1 | DHCP Assigned | DHCP Assigned | N/A | |
| S0/0/0 | 10.1.1.2 | 255.255.255.252 | N/A | |
| S0/0/1 | 10.2.2.2 | 255.255.255.252 | N/A | |
| R3 | G0/0 | 192.168.30.1 | 255.255.255.0 | N/A |
| S0/0/1 | 10.2.2.1 | 255.255.255.252 | N/A | |
| PC1 | NIC | DHCP Assigned | DHCP Assigned | DHCP Assigned |
| PC2 | NIC | DHCP Assigned | DHCP Assigned | DHCP Assigned |
| DNS Server | NIC | 192.168.20.254 | 255.255.255.0 | 192.168.20.1 |
Objectives
- Part 1: Configure a Router as a DHCP Server
- Part 2: Configure DHCP Relay
- Part 3: Configure a Router as a DHCP Client
- Part 4: Verify DHCP and Connectivity
Scenario
A dedicated DHCP server is scalable and relatively easy to manage but it can be costly to have one at every location in a network. However, a Cisco router can be configured to provide DHCP services without the need for a dedicated server. As the network technician for your company, you have been assigned the task of configuring a Cisco router as a DHCP server. You are also required to configure the edge router as a DHCP client so that it receives an IP address from the ISP network.
Instructions
Part 1: Configure a Router as a DHCP Server
Step 1: Configure the excluded IPv4 addresses.
Addresses that have been statically assigned to devices in the networks that will use DHCP must be excluded from the DHCP pools. This avoids errors associated with duplicate IP addresses. In this case the IP addresses of the R1 and R3 LAN interfaces must be excluded from DHCP. In addition, nine other addresses are excluded for static assignment to other devices such servers and device management interfaces.
a. Configure R2 to exclude the first 10 addresses from the R1 LAN.
R2(config)# ip dhcp excluded-address 192.168.10.1 192.168.10.10
b. Configure R2 to exclude the first 10 addresses from R3 LAN.
R2(config)# ip dhcp excluded-address 192.168.30.1 192.168.30.10Step 2: Create a DHCP pool on R2 for the R1 LAN.
a. Create a DHCP pool named R1-LAN (case-sensitive).
R2(config)# ip dhcp pool R1-LAN
b. Configure the DHCP pool to include the network address, the default gateway, and the IP address of the DNS server.
R2(dhcp-config)# network 192.168.10.0 255.255.255.0 R2(dhcp-config)# default-router 192.168.10.1 R2(dhcp-config)# dns-server 192.168.20.254
Step 3: Create a DHCP pool on R2 for the R3 LAN.
a. Create a DHCP pool named R3-LAN (case-sensitive).
R2(config)# ip dhcp pool R3-LANb. Configure the DHCP pool to include the network address, the default gateway, and the IP address of the DNS server. Refer to the Addressing Table.
R2(dhcp-config)# network 192.168.30.0 255.255.255.0 R2(dhcp-config)# default-router 192.168.30.1 R2(dhcp-config)# dns-server 192.168.20.254
Part 2: Configure DHCP Relay
Step 1: Configure R1 and R3 as a DHCP relay agent.
For DHCP clients to obtain an address from a server on a different LAN segment, the interface that the clients are attached to must include a helper address pointing to the DHCP server. In this case, the hosts on the LANs that are attached to R1 and R3 will access the DHCP server that is configured on R2. The IP addresses of the R2 serial interfaces that are attached to R1 and R3 are used as the helper addresses. DHCP traffic from the hosts on the R1 and R3 LANs will be forwarded to these addresses and processed by the DHCP server that is configured on R2.
a. Configure the helper address for the LAN interface on R1.
R1(config)# interface g0/0 R1(config-if)# ip helper-address 10.1.1.2
b. Configure the helper address for the LAN interface on R3.
R3(config)# interface g0/0 R3(config-if)# ip helper-address 10.2.2.2
Step 2: Configure hosts to receive IP addressing information from DHCP.
a. Configure hosts PC1 and PC2 to receive their IP addresses from a DHCP server.
b. Verify that the hosts have received their addresses from the correct DHCP pools.
Part 3: Configure a Router as a DHCP Client
Just as a PC is able to receive an IPv4 address from a server, a router interface has the ability to do the same. Router R2 needs to be configured to receive addressing from the ISP.
a. Configure the Gigabit Ethernet 0/1 interface on R2 to receive IP addressing from DHCP and activate the interface.
R2(config)# interface g0/1 R2(config-if)# ip address dhcp R2(config-if)# no shutdown
Note: Use Packet Tracer Fast Forward Time feature to speed up the process.
b. Use the show ip interface brief command to verify that R2 received an IP address from DHCP.
R2#show ip int brief Interface IP-Address OK? Method Status Protocol GigabitEthernet0/0 192.168.20.1 YES manual up up GigabitEthernet0/1 209.165.200.231 YES DHCP up up Serial0/0/0 10.1.1.2 YES manual up up Serial0/0/1 10.2.2.2 YES manual up up Serial0/1/0 unassigned YES unset down down Serial0/1/1 unassigned YES unset down down Vlan1 unassigned YES unset administratively down down R2#
Part 4: Verify DHCP and Connectivity
Step 1: Verify DHCP bindings.
R2# show ip dhcp binding
IP address Client-ID/ Lease expiration Type
Hardware address
192.168.10.11 0002.4AA5.1470 -- Automatic
192.168.30.11 0004.9A97.2535 -- AutomaticStep 2: Verify configurations.
Verify that PC1 and PC2 can now ping each other and all other devices.
Device Configs - Final
Router R1
! ============================================================== !--- 7.2.10 Packet Tracer - Configure DHCPv4 !--- ANSWER SCRIPT FOR ROUTER R1 !--- Usage: from the console (or a Telnet/SSH session, if already reachable) on R1, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. This script assumes R1's LAN/WAN interfaces are already up and addressed from a previous activity - it only adds the DHCP relay command this lab actually asks for. !--- R1's LAN (192.168.10.0/24) has no local DHCP server - PC1 needs to reach the DHCP pool configured on R2, across the R1-R2 serial link. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 2, Step 1: Configure the DHCP relay (helper address) on the LAN interface ! -------------------------------------------------------------- !--- Points at R2's S0/0/0 address (the serial interface facing R1) - DHCP broadcasts from PC1 get relayed there and processed by R2's R1-LAN pool. interface GigabitEthernet0/0 ip helper-address 10.1.1.2 end ! -------------------------------------------------------------- !--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- R1# show running-config interface g0/0 -> shows "ip helper-address 10.1.1.2" !--- From PC1, set NIC to DHCP -> should receive an address in 192.168.10.11-254 (per the excluded range configured on R2), gateway 192.168.10.1, DNS 192.168.20.254 ! ==============================================================
Router R2
! ============================================================== !--- 7.2.10 Packet Tracer - Configure DHCPv4 !--- ANSWER SCRIPT FOR ROUTER R2 !--- Usage: from the console (or a Telnet/SSH session, if already reachable) on R2, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. This script assumes R2's LAN/WAN interfaces are already up and addressed from a previous activity (except G0/1, which this lab brings up via DHCP) - it only adds the DHCP server and DHCP client commands this lab actually asks for. !--- R2 plays two DHCP roles here: it's the DHCP SERVER for both R1's and R3's remote LANs (reached via relay), and it's a DHCP CLIENT itself on G0/1, getting its own address from the ISP. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 1, Step 1: Exclude statically-assigned addresses from both pools ! -------------------------------------------------------------- !--- Excludes the first 10 addresses of each remote LAN (the router's own LAN IP plus 9 more reserved for servers/management devices) so the DHCP pools never hand these out. ip dhcp excluded-address 192.168.10.1 192.168.10.10 ip dhcp excluded-address 192.168.30.1 192.168.30.10 ! -------------------------------------------------------------- !--- Part 1, Step 2: Create the DHCP pool for the R1 LAN ! -------------------------------------------------------------- ip dhcp pool R1-LAN network 192.168.10.0 255.255.255.0 default-router 192.168.10.1 dns-server 192.168.20.254 ! -------------------------------------------------------------- !--- Part 1, Step 3: Create the DHCP pool for the R3 LAN ! -------------------------------------------------------------- ip dhcp pool R3-LAN network 192.168.30.0 255.255.255.0 default-router 192.168.30.1 dns-server 192.168.20.254 ! -------------------------------------------------------------- !--- Part 3: Configure R2 itself as a DHCP client toward the ISP ! -------------------------------------------------------------- !--- G0/1 pulls its own address from the ISP's DHCP server instead of a static one - this interface starts shut down, so "no shutdown" is required for the DHCP negotiation to even begin. interface GigabitEthernet0/1 ip address dhcp no shutdown end ! -------------------------------------------------------------- !--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- R2# show ip dhcp binding -> shows leases for PC1 (192.168.10.11) and PC2 (192.168.30.11), matching the lab's own sample output !--- R2# show ip interface brief -> G0/1 shows an address learned from the ISP (use Packet Tracer's "Fast Forward Time" to speed this up) !--- From PC1, set NIC to DHCP -> receives 192.168.10.11+, gateway 192.168.10.1, DNS 192.168.20.254 !--- From PC2, set NIC to DHCP -> receives 192.168.30.11+, gateway 192.168.30.1, DNS 192.168.20.254 !--- From PC1, ping PC2 and all other devices -> success, per Part 4's verification step ! ==============================================================
Router R3
! ============================================================== !--- 7.2.10 Packet Tracer - Configure DHCPv4 !--- ANSWER SCRIPT FOR ROUTER R3 !--- Usage: from the console (or a Telnet/SSH session, if already reachable) on R3, enter privileged EXEC mode with "enable", then paste this whole file. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. This script assumes R3's LAN/WAN interfaces are already up and addressed from a previous activity - it only adds the DHCP relay command this lab actually asks for. !--- R3's LAN (192.168.30.0/24) has no local DHCP server - PC2 needs to reach the DHCP pool configured on R2, across the R3-R2 serial link. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 2, Step 2: Configure the DHCP relay (helper address) on the LAN interface ! -------------------------------------------------------------- !--- Points at R2's S0/0/1 address (the serial interface facing R3) - DHCP broadcasts from PC2 get relayed there and processed by R2's R3-LAN pool. interface GigabitEthernet0/0 ip helper-address 10.2.2.2 end ! -------------------------------------------------------------- !--- Operational habit (not explicitly required by this lab): save to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- R3# show running-config interface g0/0 -> shows "ip helper-address 10.2.2.2" !--- From PC2, set NIC to DHCP -> should receive an address in 192.168.30.11-254, gateway 192.168.30.1, DNS 192.168.20.254 ! ==============================================================
Download Packet Tracer (.pka) file:
Previous Lab
6.4.1 Packet Tracer – Implement Etherchannel
