Topology
Addressing Table
Device
|
Interface
|
IP Address
|
Subnet Mask
|
Default Gateway
|
R1
|
G0/0
|
192.168.0.1
|
255.255.255.128
|
N/A
|
|
G0/1
|
192.168.1.1
|
255.255.255.0
|
N/A
|
|
S0/0/0 (DCE)
|
192.168.0.253
|
255.255.255.252
|
N/A
|
R2
|
S0/0/0
|
192.168.0.254
|
255.255.255.252
|
N/A
|
|
S0/0/1 (DCE)
|
209.165.200.226
|
255.255.255.252
|
N/A
|
ISP
|
S0/0/1
|
209.165.200.225
|
255.255.255.252
|
N/A
|
S1
|
VLAN 1
|
192.168.1.2
|
255.255.255.0
|
192.168.1.1
|
S2
|
VLAN 1
|
192.168.0.2
|
255.255.255.128
|
192.168.0.1
|
PC-A
|
NIC
|
DHCP
|
DHCP
|
DHCP
|
PC-B
|
NIC
|
DHCP
|
DHCP
|
DHCP
|
Objectives
Part 1: Build the Network and
Configure Basic Device Settings
Part 2: Troubleshoot DHCPv4 Issues
Background / Scenario
The Dynamic Host Configuration Protocol (DHCP)
is a network protocol that lets the network administrators manage and automate
the assignment of IP addresses. Without DHCP, the administrator must manually
assign and configure IP addresses, preferred DNS servers, and the default
gateway. As the network grows in size, this becomes an administrative problem
when devices are moved from one internal network to another.
In this scenario, the company has grown
in size, and the network administrators can no longer assign IP addresses to
devices manually. The R2 router has been configured as a DHCP server to assign
IP addresses to the host devices on router R1 LANs. Several errors in the
configuration have resulted in connectivity issues. You are asked to
troubleshoot and correct the configuration errors and document your work.
Ensure that the network supports the
following:
1)
The router R2 should function as
the DHCP server for the 192.168.0.0/25 and 192.168.1.0/24 networks connected to
R1.
2)
All PCs connected to S1 and S2
should receive an IP address in the correct network via DHCP.
Note: The routers used with CCNA hands-on labs
are Cisco 1941 Integrated Services Routers (ISRs) with Cisco IOS Release 15.2(4)M3
(universalk9 image). The switches used are Cisco Catalyst 2960s with Cisco IOS Release
15.0(2) (lanbasek9 image). Other routers, switches and Cisco IOS versions can
be used. Depending on the model and Cisco IOS version, the commands available
and output produced might vary from what is shown in the labs. Refer to the
Router Interface Summary Table at the end of this lab for the correct interface
identifiers.
Note: Make sure that the routers and switches have been erased and have
no startup configurations. If you are unsure, contact your instructor.
Required Resources
·
3 Routers (Cisco 1941 with
Cisco IOS Release 15.2(4)M3 universal image or comparable)
·
2 Switches (Cisco 2960 with
Cisco IOS Release 15.0(2) lanbasek9 image or comparable)
·
2 PCs (Windows 7, Vista, or XP
with terminal emulation program, such as Tera Term)
·
Console cables to configure the
Cisco IOS devices via the console ports
·
Ethernet and serial cables as
shown in the topology
Part 1:
Build the Network and Configure
Basic Device Settings
In Part 1, you will set up the network
topology and configure the routers and switches with basic settings, such as
passwords and IP addresses. You will also configure the IP settings for the PCs
in the topology.
Step 1:
Cable the network as shown in
the topology.
Step 2:
Initialize and reload the
routers and switches.
Step 3:
Configure basic settings for each
router.
a.
Disable DNS lookup.
b.
Configure device name as shown
in the topology.
c.
Assign class as the privileged EXEC password.
d.
Assign cisco as the console and vty passwords.
e.
Configure logging synchronous to prevent console messages from interrupting
command entry.
f.
Configure the IP addresses for
all the router interfaces.
g.
Set clock rate to 128000 for all DCE router interfaces.
h.
Configure RIP for R1.
R1(config)# router
rip
R1(config-router)# version 2
R1(config-router)# network 192.168.0.0
R1(config-router)# network 192.168.1.0
R1(config-router)# no auto-summary
R1(config-router)# exit
i.
Configure RIP and a static
default route on R2.
R2(config)# router
rip
R2(config-router)# version 2
R2(config-router)# network 192.168.0.0
R2(config-router)# default-information originate
R2(config-router)# no auto-summary
R2(config-router)# exit
R2(config)# ip
route 0.0.0.0 0.0.0.0 209.165.200.225
j.
Configure a summary static
route on ISP to the networks on R1 and R2 routers.
ISP(config)# ip
route 192.168.0.0 255.255.254.0 209.165.200.226
Step 4:
Verify network connectivity
between the routers.
If any pings between the routers fail,
correct the errors before proceeding to the next step. Use show ip route and show ip
interface brief to locate possible issues.
Step 5:
Configure basic settings for
each switch.
a.
Disable DNS lookup.
b.
Configure device name as shown
in the topology.
c.
Configure the IP address for the
VLAN 1 interface and the default gateway for each switch.
d.
Assign class as the privileged EXEC mode password.
e.
Assign cisco as the console and vty passwords.
f.
Configure logging synchronous for the console line.
Step 6:
Verify the hosts are configured
for DHCP.
Step 7:
Load the initial DHCP
configuration for R1 and R2.
Router R1
interface GigabitEthernet0/1
ip
helper-address 192.168.0.253
Router R2
ip dhcp excluded-address 192.168.11.1 192.168.11.9
ip dhcp excluded-address 192.168.0.1 192.168.0.9
ip dhcp pool R1G1
network
192.168.1.0 255.255.255.0
default-router 192.168.1.1
ip dhcp pool R1G0
network
192.168.0.0 255.255.255.128
default-router 192.168.11.1
Part 2:
Troubleshoot DHCPv4 Issues
After configuring routers R1 and R2 with DHCPv4
settings, several errors in the DHCP configurations were introduced and
resulted in connectivity issues. R2 is configured as a DHCP server. For both
pools of DHCP addresses, the first nine addresses are reserved for the routers
and switches. R1 relays the DHCP information to all the R1 LANs. Currently,
PC-A and PC-B have no access to the network. Use the show and debug commands
to determine and correct the network connectivity issues.
Step 1:
Record IP settings for PC-A and
PC-B.
a.
For PC-A and PC-B, at the
command prompt, enter ipconfig /all to
display the IP and MAC addresses.
b.
Record the IP and MAC addresses
in the table below. The MAC address can be used to determine which PC is
involved in the debug message.
|
IP Address/Subnet Mask
|
MAC Address
|
PC-A
|
|
|
PC-B
|
|
|
Step 2:
Troubleshoot DHCP issues for the
192.168.1.0/24 network on router R1.
Router R1 is a DHCP relay agent for all
the R1 LANs. In this step, only the DHCP process for the 192.168.1.0/24 network
will be examined. The first nine addresses are reserved for other network
devices, such as routers, switches, and servers.
a.
Use a DHCP debug command to observe the DHCP process on R2 router.
R2# debug
ip dhcp server events
b.
On R1, display the
running configuration for the G0/1 interface.
R1# show
run interface g0/1
interface GigabitEthernet0/1
ip address
192.168.1.1 255.255.255.0
ip
helper-address 192.168.0.253
duplex
auto
speed auto
If there are any DHCP relay issues,
record any commands that are necessary to correct the configurations errors.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
c.
In a command prompt on PC-A,
type ipconfig /renew to receive an
address from the DHCP server. Record the configured IP address, subnet mask, and
default gateway for PC-A.
____________________________________________________________________________________
d.
Observe the debug messages on
R2 router for the DHCP renewal process for PC-A. The DHCP server attempted to
assign 192.168.1.1/24 to PC-A. This address is already in use for G0/1
interface on R1. The same issue occurs with IP address 192.168.1.2/24 because
this address has been assigned to S1 in the initial configuration. Therefore,
an IP address of 192.168.1.3/24 has been assigned to PC-A. The DHCP assignment
conflict indicates there may be an issue with the excluded-address statement on
the DHCP server configuration on R2.
*Mar
5 06:32:16.939: DHCPD: Sending notification of DISCOVER:
*Mar
5 06:32:16.939: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:32:16.939: DHCPD: circuit
id 00000000
*Mar
5 06:32:16.939: DHCPD: Seeing if there is an internally specified pool
class:
*Mar
5 06:32:16.939: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:32:16.939: DHCPD: circuit
id 00000000
*Mar
5 06:32:16.943: DHCPD: Allocated binding 2944C764
*Mar
5 06:32:16.943: DHCPD: Adding binding to radix tree (192.168.1.1)
*Mar
5 06:32:16.943: DHCPD: Adding binding to hash tree
*Mar
5 06:32:16.943: DHCPD: assigned IP address 192.168.1.1 to client 0100.5056.be76.8c.
*Mar 5 06:32:16.951:
%DHCPD-4-PING_CONFLICT: DHCP address conflict:
server pinged 192.168.1.1.
*Mar 5 06:32:16.951: DHCPD:
returned 192.168.1.1 to address pool R1G1.
*Mar
5 06:32:16.951: DHCPD: Sending notification of DISCOVER:
*Mar
5 06:32:16.951: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:32:16.951: DHCPD: circuit
id 00000000
*Mar
5 06:32:1
R2#6.951: DHCPD: Seeing if there is an
internally specified pool class:
*Mar
5 06:32:16.951: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:32:16.951: DHCPD: circuit
id 00000000
*Mar
5 06:32:16.951: DHCPD: Allocated binding 31DC93C8
*Mar
5 06:32:16.951: DHCPD: Adding binding to radix tree (192.168.1.2)
*Mar
5 06:32:16.951: DHCPD: Adding binding to hash tree
*Mar
5 06:32:16.951: DHCPD:
assigned IP address 192.168.1.2 to client 0100.5056.be76.8c.
*Mar 5 06:32:18.383:
%DHCPD-4-PING_CONFLICT: DHCP address conflict:
server pinged 192.168.1.2.
*Mar
5 06:32:18.383: DHCPD: returned 192.168.1.2 to address pool R1G1.
*Mar
5 06:32:18.383: DHCPD: Sending notification of DISCOVER:
*Mar
5 06:32:18.383: DHCPD: htype 1
chaddr 0050.56be.6c89
*Mar
5 06:32:18.383: DHCPD: circuit
id 00000000
*Mar
5 06:32:18.383: DHCPD: Seeing if there is an internally specified pool
class:
*Mar
5 06:32:18.383: DHCPD: htype 1
chaddr 0050.56be.6c89
*Mar
5 06:32:18.383: DHCPD: circuit
id 00000000
*Mar
5 06:32:18.383: DHCPD: Allocated binding 2A40E074
*Mar
5 06:32:18.383: DHCPD: Adding binding to radix tree (192.168.1.3)
*Mar
5 06:32:18.383: DHCPD: Adding binding to hash tree
*Mar 5 06:32:18.383: DHCPD:
assigned IP address 192.168.1.3 to client 0100.5056.be76.8c.
<output omitted>
e.
Display the DHCP server
configuration on R2. The first nine addresses for 192.168.1.0/24 network are
not excluded from the DHCP pool.
R2# show
run | section dhcp
ip dhcp excluded-address 192.168.11.1 192.168.11.9
ip dhcp excluded-address 192.168.0.1
192.168.0.9
ip dhcp pool R1G1
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
ip dhcp pool R1G0
network 192.168.0.0 255.255.255.128
default-router 192.168.1.1
Record the commands to resolve the issue
on R2.
____________________________________________________________________________________
____________________________________________________________________________________
f.
At the command prompt on PC-A,
type ipconfig /release to return the
192.168.1.3 address back to the DHCP pool. The process can be observed in the
debug message on R2.
*Mar
5 06:49:59.563: DHCPD: Sending notification of TERMINATION:
*Mar
5 06:49:59.563: DHCPD: address
192.168.1.3 mask 255.255.255.0
*Mar
5 06:49:59.563: DHCPD: reason
flags: RELEASE
*Mar
5 06:49:59.563: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:49:59.563: DHCPD: lease
time remaining (secs) = 85340
*Mar
5 06:49:59.563: DHCPD:
returned 192.168.1.3 to address pool R1G1.
g.
At the command prompt on PC-A,
type ipconfig /renew to be assigned
a new IP address from the DHCP server. Record the assigned IP address and
default gateway information.
____________________________________________________________________________________
The process can be observed in the debug
message on R2.
*Mar
5 06:50:11.863: DHCPD: Sending notification of DISCOVER:
*Mar
5 06:50:11.863: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:50:11.863: DHCPD: circuit
id 00000000
*Mar
5 06:50:11.863: DHCPD: Seeing if there is an internally specified pool
class:
*Mar
5 06:50:11.863: DHCPD: htype 1
chaddr 0050.56be.768c
*Mar
5 06:50:11.863: DHCPD: circuit
id 00000000
*Mar
5 06:50:11.863: DHCPD: requested address 192.168.1.3 has already been
assigned.
*Mar
5 06:50:11.863: DHCPD: Allocated binding 3003018C
*Mar
5 06:50:11.863: DHCPD: Adding binding to radix tree (192.168.1.10)
*Mar
5 06:50:11.863: DHCPD: Adding binding to hash tree
*Mar
5 06:50:11.863: DHCPD: assigned IP address 192.168.1.10 to client 0100.5056.be76.8c.
<output omitted>
h.
Verify network connectivity.
Can PC-A ping the assigned default
gateway? ___________
Can PC-A ping
the R2 router? ___________
Can PC-A ping the ISP router? ___________
Step 3:
Troubleshoot DHCP issues for
192.168.0.0/25 network on R1.
Router R1 is a DHCP relay agent for all
the R1 LANs. In this step, only the DHCP process for the 192.168.0.0/25 network
is examined. The first nine addresses are reserved for other network devices.
a.
Use a DHCP debug command to observe the DHCP process on R2.
R2# debug
ip dhcp server events
b.
Display the running
configuration for the G0/0 interface on R1 to identify possible DHCP issues.
R1# show
run interface g0/0
interface GigabitEthernet0/0
ip address
192.168.0.1 255.255.255.128
duplex
auto
speed auto
Record the issues and any commands that are
necessary to correct the configurations errors.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
c.
From the command prompt on
PC-B, type ipconfig /renew to
receive an address from the DHCP server. Record the configured IP address,
subnet mask, and default gateway for PC-B.
____________________________________________________________________________________
d.
Observe the debug messages on
R2 router for the renewal process for PC-A. The DHCP server assigned
192.168.0.10/25 to PC-B.
*Mar
5 07:15:09.663: DHCPD: Sending notification of DISCOVER:
*Mar
5 07:15:09.663: DHCPD: htype 1
chaddr 0050.56be.f6db
*Mar
5 07:15:09.663: DHCPD: circuit
id 00000000
*Mar
5 07:15:09.663: DHCPD: Seeing if there is an internally specified pool
class:
*Mar
5 07:15:09.663: DHCPD: htype 1
chaddr 0050.56be.f6db
*Mar
5 07:15:09.663: DHCPD: circuit
id 00000000
*Mar
5 07:15:09.707: DHCPD:
Sending notification of ASSIGNMENT:
*Mar
5 07:15:09.707: DHCPD: address 192.168.0.10 mask
255.255.255.128
*Mar
5 07:15:09.707: DHCPD: htype 1
chaddr 0050.56be.f6db
*Mar
5 07:15:09.707: DHCPD: lease
time remaining (secs) = 86400
e.
Verify network connectivity.
Can PC-B ping the DHCP assigned default
gateway? ___________
Can PC-B ping its default gateway
(192.168.0.1)? ___________
Can PC-B ping the R2 router? ___________
Can PC-B ping the ISP router? ___________
f.
If any issues failed in Step e,
record the problems and any commands to resolve the issues.
____________________________________________________________________________________
____________________________________________________________________________________
g.
Release and renew the IP
configurations on PC-B. Repeat Step e to verify network connectivity.
h.
Discontinue the debug process
by using the undebug all command.
R2# undebug
all
All possible debugging has been turned off
Reflection
What are the benefits of using DHCP?
_______________________________________________________________________________________
_______________________________________________________________________________________
Router Interface Summary Table
Router Interface Summary
|
||||
Router Model
|
Ethernet Interface #1
|
Ethernet Interface #2
|
Serial Interface #1
|
Serial Interface #2
|
1800
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
1900
|
Gigabit Ethernet 0/0 (G0/0)
|
Gigabit Ethernet 0/1 (G0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
2801
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/1/0 (S0/1/0)
|
Serial 0/1/1 (S0/1/1)
|
2811
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
2900
|
Gigabit Ethernet 0/0 (G0/0)
|
Gigabit Ethernet 0/1 (G0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
Note: To find out how the router is configured, look at the interfaces
to identify the type of router and how many interfaces the router has. There
is no way to effectively list all the combinations of configurations for each
router class. This table includes identifiers for the possible combinations
of Ethernet and Serial interfaces in the device. The table does not include
any other type of interface, even though a specific router may contain one.
An example of this might be an ISDN BRI interface. The string in parenthesis
is the legal abbreviation that can be used in Cisco IOS commands to represent
the interface.
|
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