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Verifying a DHCP Server Configuration
To verify a DHCP server configuration, perform the following tasks:
Displaying a DHCP Server
Configuration
Purpose
Verify the configuration of a DHCP server.
Action
From the J-Web interface, select Configuration>View and Edit>View Configuration Text.
Alternatively, from configuration mode in the CLI, enter the show system
services dhcp command from the top level.
You can
also view the IP address pool from the CLI in operational mode by entering
the show system services dhcp pool command.
[edit]
user@host# show system services dhcp
pool 192.168.2.0/24 {
address-range low 192.168.2.2 high 192.168.2.254;
exclude-address {
192.168.2.33;
}
maximum-lease-time 2419200;
default-lease-time 1209600;
name-server {
192.168.10.2;
}
domain-search {
mycompany.net;
mylab.net;
}
option 16 ip-address 192.168.2.33;
}
static-binding 01.03.05.07.09.0b {
fixed-address {
192.168.2.50;
}
}
What it Means
Verify that the output shows the intended configuration of the DHCP
server. For more information about the format of a configuration file, see
the J-series Services Router Basic LAN and WAN Access Configuration Guide.
Verifying the DHCP Binding Database
Purpose
Verify that the DHCP binding database reflects your DHCP server configuration.
Action
From operational mode in the CLI, to display all active bindings
in the database, enter the show system services dhcp binding command.
To display all bindings in the database, including their current binding state,
enter the show system services dhcp binding detail command. To display
more information about a client, including its DHCP options, enter the show
system services dhcp binding ip-address detail command,
replacing ip-address with the IP address of the client.
The DHCP binding database resulting
from the configuration defined in Configuring the DHCP Server with a Configuration Editor is
displayed in the following sample output.
To clear the DHCP binding
database, enter the clear system services dhcp binding command. To
remove a specific entry from the DHCP binding database, enter the clear
system services dhcp binding ip-address command,
replacing ip-address with the IP address of the client.
You
can also use the J-Web interface to view information in the DHCP binding database.
For more information, see Monitoring DHCP.
| |
user@host> show system services dhcp binding
IP Address Hardware Address Type Lease expires at
192.168.2.2 02:04:06:08:0A:0C dynamic 2005-02-07 8:48:59 PDT
192.168.2.50 01:03:05:07:09:0B static never
|
| |
user@host> show system services dhcp binding
192.168.2.2 detail
IP address 192.168.2.2
Hardware address 02:04:06:08:0A:0C
Pool 192.168.2.0/24
Request received on fe-0/0/0
Lease information:
Type DHCP
Obtained at 2005-01-24 8:48:59 PDT
Expires at 2005-02-07 8:48:59 PDT
State active
DHCP options:
Name: domain-name, Value: mycompany.net mylab.net
Name: name-server, Value: 192.168.10.2
Code: 16, Type: ip-address, Value: 192.168.2.33
|
| |
user@host> show system services dhcp conflict
|
What it Means
Verify the following information:
- For each dynamic binding, verify that the IP address is within
the range of the configured IP address pool. Under Lease Expires,
verify that the difference between the date and time when the lease expires
and the current date and time is less than the maximum configured lease time.
- For each static binding, verify that the IP address corresponds
to the MAC address displayed under Hardware Address (as defined in
the static-binding statement in the configuration). Under Lease
Expires, verify that the lease expiration is never.
- In the output displayed by the show system services dhcp binding ip-address detail command,
verify that the options under DHCP options are correct for the subnet.
- Verify that the show system services dhcp conflict command
does not display any conflicts.
Verifying DHCP Server Operation
Purpose
Verify that the DHCP server is operating as configured.
Action
Take the following actions:
- Use the ping command to verify that a client responds
to ping packets containing the destination IP address assigned by the Services Router.
- Display the IP configuration on the client. For example, on a
PC running Microsoft Windows, enter ipconfig /all at the command
prompt to display the PC's IP configuration.
| |
user@host> ping 192.168.2.2
PING 192.168.2.2 (192.168.2.2): 56 data bytes
64 bytes from 192.168.2.2: icmp_seq=0 ttl=255 time=8.856 ms
64 bytes from 192.168.2.2: icmp_seq=1 ttl=255 time=11.543 ms
64 bytes from 192.168.2.2: icmp_seq=2 ttl=255 time=10.315 ms
...
|
| |
C:\Documents and Settings\user> ipconfig /all
Windows 2000 IP Configuration
Host Name . . . . . . . . . . . . : my-pc
Primary DNS Suffix . . . . . . . : mycompany.net
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : mycompany.net
mylab.net
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . : mycompany.net mylab.net
Description . . . . . . . . . . . : 10/100 LAN Fast Ethernet Card
Physical Address. . . . . . . . . : 02-04-06-08-0A-0C
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.2.2
Subnet Mask . . . . . . . . . . . : 255.255.254.0
Default Gateway . . . . . . . . . : 192.168.10.3
DHCP Server . . . . . . . . . . . : 192.168.2.1
DNS Servers . . . . . . . . . . . : 192.168.10.2
Primary WINS Server . . . . . . . : 192.168.10.4
Secondary WINS Server . . . . . . : 192.168.10.5
Lease Obtained. . . . . . . . . . : Monday, January 24, 2005 8:48:59 AM
Lease Expires . . . . . . . . . . : Monday, February 7, 2005 8:48:59 AM
|
What it Means
Verify the following:
- The client returns a ping response.
For information about using the J-Web interface to ping
a host, see Using the J-Web Ping
Host Tool. For more
information about the ping command, see Pinging Hosts from the CLI or
the JUNOS System Basics and Services Command Reference.
- The client IP configuration displayed contains the configured
values. For example, for the DHCP configuration in Configuring the DHCP Server with a Configuration Editor,
you can verify the following settings:
- DNS Suffix Search List is correct.
- IP address is within the IP address pool you configured.
- DHCP Server is the primary IP address of the Services Router interface
on which the DHCP message exchange occurs. If you include the server-identifier statement
in your configuration, the DHCP server IP address specified in this statement
is displayed.
- Lease Obtained and Lease Expires times are correct.
The ipconfig command also displays other DHCP client
settings that can be configured on the Services Router, including the
client's hostname, default gateways, and WINS servers.
Displaying DHCP Statistics
Purpose
Display DHCP statistics, including lease times, packets dropped, and
DHCP and BOOTP messages received and sent, to verify normal operation.
Action
Enter the show system services dhcp
statistics command to display the DHCP statistics.
| |
user@host> show system services dhcp statistics
Packets dropped:
Total 0
Messages received:
BOOTREQUEST 0
DHCPDECLINE 0
DHCPDISCOVER 0
DHCPINFORM 0
DHCPRELEASE 0
DHCPREQUEST 78
Messages sent:
BOOTREPLY 0
DHCPOFFER 0
DHCPACK 78
DHCPNAK 0
|
What it Means
Verify the following:
- The default settings displayed are consistent with your DHCP server
configuration.
- The number of dropped packets and errors is small.
- DHCPREQUEST messages have been received and DHCPACK messages have
been sent.
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