Administrator Guide

To view the ip helper-address configuration for an interface, use the show ip interface command from EXEC privilege mode.
Example of the show ip interface Command
R1_E600#show ip int gig 1/3
GigabitEthernet 1/3 is up, line protocol is down
Internet address is 10.11.0.1/24
Broadcast address is 10.11.0.255
Address determined by user input
IP MTU is 1500 bytes
Helper address is 192.168.0.1
192.168.0.2
Directed broadcast forwarding is disabled
Proxy ARP is enabled
Split Horizon is enabled
Poison Reverse is disabled
ICMP redirects are not sent
ICMP unreachables are not sent
Configure the System to be a DHCP Client
A DHCP client is a network device that requests an IP address and configuration parameters from a DHCP server.
Implement the DHCP client functionality as follows:
• The switch can obtain a dynamically assigned IP address from a DHCP server. A start-up configuration is not received. Use bare metal
provisioning (BMP) to receive configuration parameters (OS version and a configuration file). BMP is enabled as a factory-default
setting on a switch.
A switch cannot operate with BMP and as a DHCP client simultaneously. To disable BMP in EXEC mode, use the stop bmp
command. After BMP stops, the switch acts as a DHCP client.
• Acquire a dynamic IP address from a DHCP client is for a limited period or until the client releases the address.
• A DHCP server manages and assigns IP addresses to clients from an address pool stored on the server. For more information, refer to
Configuring the Server for Automatic Address Allocation.
• Dynamically assigned IP addresses are supported on 10-Gigabit and 40-Gigabit interfaces. The DHCP client is supported on VLAN and
port-channel interfaces.
• The public out-of-band management interface and default VLAN 1 are configured by default as a DHCP client to acquire a dynamic IP
address from a DHCP server.
DHCP Client on a Management Interface
These conditions apply when you enable a management interface to operate as a DHCP client.
• The management default route is added with the gateway as the router IP address received in the DHCP ACK packet. It is required to
send and receive traffic to and from other subnets on the external network. The route is added irrespective when the DHCP client and
server are in the same or different subnets. The management default route is deleted if the management IP address is released like
other DHCP client management routes.
• ip route for 0.0.0.0 takes precedence if it is present or added later.
• Management routes added by a DHCP client display with Route Source as DHCP in the show ip management route and show
ip management-route dynamic command output.
• Management routes added by DHCP are automatically reinstalled if you configure a static IP route with the ip route command that
replaces a management route added by the DHCP client. If you remove the statically configured IP route using the no ip route
command, the management route is reinstalled. Manually delete management routes added by the DHCP client.
• To reinstall management routes added by the DHCP client that is removed or replaced by the same statically configured management
routes, release the DHCP IP address and renew it on the management interface.
• Management routes added by the DHCP client have higher precedence over the same statically configured management route. Static
routes are not removed from the running configuration if a dynamically acquired management route added by the DHCP client
overwrites a static management route.
• Management routes added by the DHCP client are not added to the running configuration.
NOTE:
Management routes added by the DHCP client include the specific routes to reach a DHCP server in a different
subnet and the management route.
Dynamic Host Configuration Protocol (DHCP) 319