Service Manual

DHCP client and server are in the same or dierent 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 congure a static IP route with the ip route
command that replaces a management route added by the DHCP client. If you remove the statically congured 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 congured
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 congured management route.
Static routes are not removed from the running conguration 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 conguration.
NOTE: Management routes added by the DHCP client include the specic routes to reach a DHCP server in a dierent
subnet and the management route.
DHCP Client Operation with Other Features
The DHCP client operates with other Dell Networking OS features, as the following describes.
Stacking
The DHCP client daemon runs only on the master unit and handles all DHCP packet transactions. It periodically synchronizes the
lease le with the standby unit.
When a stack failover occurs, the new master requires the same DHCP server-assigned IP address on DHCP client interfaces. The
new master reinitiates a DHCP packet transaction by sending a DHCP discovery packet on nonbound interfaces.
Virtual Link Trunking (VLT)
A DHCP client is not supported on VLT interfaces.
VLAN and Port Channels
DHCP client conguration and behavior are the same on Virtual LAN (VLAN) and port-channel (LAG) interfaces as on a physical
interface.
DHCP Snooping
A DHCP client can run on a switch simultaneously with the DHCP snooping feature as follows:
• If you enable DHCP snooping globally on a switch and you enable a DHCP client on an interface, the trust port, source MAC
address, and snooping table validations are not performed on the interface by DHCP snooping for packets destined to the DHCP
client daemon.
The following criteria determine packets destined for the DHCP client:
– DHCP is enabled on the interface.
– The user data protocol (UDP) destination port in the packet is 68.
– The chaddr (change address) in the DHCP header of the packet is the same as the interface’s MAC address.
• An entry in the DHCP snooping table is not added for a DHCP client interface.
DHCP Server
A switch can operate as a DHCP client and a DHCP server. DHCP client interfaces cannot acquire a dynamic IP address from the
DHCP server running on the switch. Acquire a dynamic IP address from another DHCP server.
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Dynamic Host Conguration Protocol (DHCP)