Enabling IP to Physical Port Mapping

You can reserve IP addresses within a DHCP address pool against selected Ethernet ports. This allows any device connecting to the selected port on the switch to obtain the same IP address irrespective of the client identifier sent by the device. This configuration is useful in preventing a newly connected device on a port from getting a new IP address.
This option works by replacing the DHCP client identifier (option 61) sent by the DHCP client with an auto-generated port name. The port name is derived from the configured port number in the DHCP address pool. The DHCP server adds DHCP client identifier (option 61) internally and assigns an IP address accordingly if the DHCP client sends the request packet without the client identifier option, and the options payload has enough space to include the auto-generated port name as a client identifier option.

The following limitations must be considered when using this option:

  • This option should be used only when the ICX switch is configured as an edge device or as a gateway intended to assign the same IP addresses to its clients.
  • Static port-IP mapping on Virtual Ethernet (VE) interfaces works only when the ip dhcp-server use-port-name command is explicitly enabled on the VE interface.
  • Only one IP address is allowed to be reserved for a selected port.
  • This option should be used only when a single device is expected to be connected on the selected port. Any additional devices connected to the same port, using a hub or a downstream switch, will result in all the devices getting assigned the same IP address.
  • Static port to IP mapping is not available on virtual interfaces, including LAGs and loopback interfaces. Only VE interfaces are supported.
  • This option works when the client identifier used is Ethernet type or if a client identifier is not present; it does not work if a string type is used as the client identifier.
Note: To achieve better scaling performance, disable the feature explicitly for an interface if a burst of DHCP client traffic is expected on a single interface. If the feature is not explicitly disabled for the interface, some of the DHCP clients may not be assigned an IP address and may need to send the request again. Similar behavior may be seen during the release of IP addresses also.

Use the following procedure to configure static port to IP mapping in a DHCP address pool.

  1. Enter global configuration mode. 
    device# configure terminal
  2. Enter interface configuration mode.
    device(config)# interface ethernet 1/1/8
  3. Enable the replacement of the DHCP client identifier (option 61) with the port name for the Interface. 
    device(config-if-e1000-1/1/8)# ip dhcp-server use-port-name enable
  4. Return to global configuration mode.
    device(config-if-e1000-1/1/8)# exit
  5. Create a DHCP server pool. 
    device(config)# ip dhcp-server pool list
  6. Configure the DHCP server address pool. 
    device(config-dhcp-list)# network 10.10.10.0 255.255.255.0
device(config-dhcp-list)# lease-count 254
device(config-dhcp-list)# lease 1 0 0
  7. Map an Ethernet interface to the IP address.
    device(config-dhcp-list)# static-port-ip-mapping 10.10.10.2 e1/1/3

The following example shows a configured static port to IP mapping.

device# configure terminal
device(config)# interface ethernet 1/1/8
device(config-if-e1000-1/1/8)# ip dhcp-server use-port-name enable
device(config-if-e1000-1/1/8)# exit
device(config)# ip dhcp-server pool list
device(config-dhcp-list)# network 10.10.10.0 255.255.255.0
device(config-dhcp-list)# lease-count 254
device(config-dhcp-list)# lease 1 0 0
device(config-dhcp-list)# static-port-ip-mapping 10.10.10.2 e1/1/3

The following example demonstrates how to configure a DHCP server pool with specific settings, including network definition, lease parameters, excluded addresses, vendor options, and static IP mapping to a VE interface on a device:

device# configure terminal
device(config)# interface ve 1
device(config-vlan-1)# ip dhcp-server use-port-name enable
device(config-vlan-1)# exit
device(config)# ip dhcp-server pool test2
device(config-dhcp-test2)# network 25.25.25.0 255.255.255.0 
device(config-dhcp-test2)# lease-count 246
device(config-dhcp-test2)# excluded-address 25.25.25.1
device(config-dhcp-test2)# excluded-address 25.25.25.2
device(config-dhcp-test2)# excluded-address 25.25.25.3
device(config-dhcp-test2)# lease 1 0 0
device(config-dhcp-test2)# option vendor-encapsulated-options ip 10.0.10.1 10.0.10.2
device(config-dhcp-test2)# static-port-ip-mapping 25.25.25.50 ve1
Parent topic: DHCP Servers