Dhcp Client Simulator Software
user@R2>configure  user@R2#set interfaces ge-0/0/0 unit 0 family inet dhcp user@R2#commit commit complete user@R2#exit  user@R2>show system services dhcp client GUI Based :
Dhcp Client Simulator Software
Cisco devices running Cisco software include Dynamic Host Configuration Protocol (DHCP) server and the relay agent software. The Cisco IOS DHCP server is a full DHCP server implementation that assigns and manages IP addresses from specified address pools within the device to DHCP clients. The DHCP server can be configured to assign additional parameters such as the IP address of the Domain Name System (DNS) server and the default device.
After an interface is enabled with the DHCP client function, the interface can obtain network parameters including the IP address from the DHCPserver. If the allocated IP address and IP addresses of other interfaces are on the same network segment, the interface does not use this IP address and does not re-apply for an IP address. To allow the interface to re-apply for an IP address, runthe shutdown and then the undo shutdown commands on the interface. Alternatively,run the undo ip address dhcp-alloc and then the ip address dhcp-alloc command on the interface.
ip address dhcp-allocBy default, the DHCP client function is enabled on VLANIF1 of the S1720GW, S1720GWR, S1720GW-E, and S1720GWR-E. The DHCP client function is disabled on the interfaces of other switches.
The default DHCP lease time used by CDRouter is 300 seconds (5 minutes). Ifseveral of the dhcp-c.tcl module tests are failing, it could be that the routerdoes not deal gracefully with a short DHCP lease time when setting up the T1 andT2 timers for DHCP. When a DHCP lease is starting to expire, some DHCP clientswill drop directly into DHCP discovery mode without attempting to send any DHCPrequest packets. This can cause several test failures in the dhcp-c.tcl module.You can adjust the DHCP lease time by setting the dhcpLeaseTimevariable in your configuration file.
NOTE: Some test cases will wait an entire DHCP lease interval. Setting the dhcpLeaseTimeto a large value will slow down test executiondramatically. We recommend trying to find the smallest value that will work withyour DHCP client.
We can add ip dhcp excluded-address command to our configuration so as to configure the router to exclude addresses 192.168.1.1 through 192.168.1.10 when assigning addresses to clients. The ip dhcp excluded-address command may be used to reserve addresses that are statically assigned to key hosts.
In order for the DHCP server to provide configuration records for clients, an appropriate configuration file needs to be created. By default, the DHCP server looks for a configuration file called dhcpd.conf under /etc. You can either edit this file or create a new one and provide its full path to the DHCP server using the -cf flag (See a file example at docs/dhcpd.conf). The DHCP server must run on a machine which has loaded the IPoIB module. To run the DHCP server from the command line, enter:
In the case of a client using DHCP for initial configuration (before the client's TCP/IP software has been completely configured), DHCP requires creative use of the client's TCP/IP software and liberal interpretation of RFC 1122. The TCP/IP software SHOULD accept and forward to the IP layer any IP packets delivered to the client's hardware address before the IP address is configured; DHCP servers and BOOTP relay agents may not be able to deliver DHCP messages to clients that cannot accept hardware unicast datagrams before the TCP/IP software is configured.
DHCP has a limitation with networks split into one or more subnets. A client request for an IP address is confined to the subnet the client exists on. To get around this limitation, a DHCP relay agent must be configured. A DHCP relay agent is a bit of software that forwards client requests and DHCP server responses across different subnets. This prevents having to have a DHCP server configured on every subnet.