Administrator Guide

You can override the DHCP-assigned address on the OOB management interface by manually
configuring an IP address using the CLI or CMC interface. If no user-configured IP address exists for
the OOB interface exists and if the OOB IP address is not in the startup configuration, the Aggregator
will automatically obtain it using DHCP.
You can also manually configure an IP address for the VLAN 1 default management interface using the
CLI. If no user-configured IP address exists for the default VLAN management interface exists and if
the default VLAN IP address is not in the startup configuration, the Aggregator will automatically
obtain it using DHCP.
• The default VLAN 1 with all ports configured as members is the only L3 interface on the Aggregator.
When the default management VLAN has a DHCP-assigned address and you reconfigure the default
VLAN ID number, the Aggregator:
– Sends a DHCP release to the DHCP server to release the IP address.
– Sends a DHCP request to obtain a new IP address. The IP address assigned by the DHCP server is
used for the new default management VLAN.
How DHCP Client is Implemented
The Aggregator is enabled by default to receive DHCP server-assigned dynamic IP addresses on an
interface. This setting persists after a switch reboot. If you enter the shutdown command on the
interface, DHCP transactions are stopped and the dynamically-acquired IP address is saved. Use the
show
interface type slot/port command to display the dynamic IP address and DHCP as the mode of
IP address assignment. If you later enter the no shutdown command and the lease timer for the
dynamic IP address has expired, the IP address is unconfigured and the interface tries to acquire a new
dynamic address from DHCP server.
If you later enter the no shutdown command and the lease timer for the dynamic IP address has
expired, the IP address is released.
When you enter the release dhcp command, although the IP address that was dynamically-acquired
from a DHCP server is released from an interface, the ability to acquire a new DHCP server-assigned
address remains in the running configuration for the interface. To acquire a new IP address, enter either
the renew dhcp command at the EXEC privilege level or the ip address dhcp command at the
interface configuration level.
If you enter renew dhcp command on an interface already configured with a dynamic IP address, the
lease time of the dynamically acquired IP address is renewed.
Important: To verify the currently configured dynamic IP address on an interface, enter the show
ip dhcp lease
command. The show running-configuration command output only displays
ip address dhcp; the currently assigned dynamic IP address is not displayed.
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.
Dynamic Host Configuration Protocol (DHCP)
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