3.3 Ports Configuration Commands

Configure Port Speed, Advertise Duplex, Advertise Speed, Flow Control, PFC (Priority Flow Control), Maximum Frame Size, Excessive Collision mode, and Frame Length Check.

Use this command to enable/disable Ethernet port (has no effect on PoE power).

Command Syntax:

shutdown

Table 3-18. Command Description
	Argument	Description
Parameter	N.A	N.A
Default	N.A
Mode	Port List Interface Configuration mode
Usage	Use the command to disable the specified interface and use ‘no’ form of this command to enable the interface.
Example	Example 1: Disable port 1. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# shutdown` Example 2: Disable ports 1 through 4. `# configure terminal (config)# interface GigabitEthernet 1/1-4 (config-if)# shutdown` Example 3: Enable all ports. `# configure terminal (config)# interface * (config-if)# no shutdown`

Use this command to configure the port speed.

Command Syntax:

speed { 10 | 100 | 1000 | auto { [ 10 ] [ 100 ] [ 1000 ] { [ no-hdx ] | [ no-fdx ] } } }

Table 3-19. Command Description
	Argument	Description
Parameter	`10`	10 Mbps
	`100`	100 Mbps
	`1000`	1000 Mbps (1 Gbps)
	`auto`	Auto negotiation
	`no-hdx`	Only advertise full duplex
	`no-fdx`	Only advertise half duplex
Default	All ports are set to Auto
Mode	Port List Interface mode
Usage	Use this command to set the speed of the specified interface.
Example	Example 1: Set speed for port 1 to 100 Mbps. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# speed 100` Example 2: Set all ports to 1 Gbps. `# configure terminal (config)# interface * (config-if)# speed 1000`

Use this command to configure the interface duplex mode.

Command Syntax:

duplex { half | full | { auto [ half | full ] } }

Table 3-20. Command Description
	Argument	Description
Parameter	`half`	Half duplex when speed is forced (non-auto)
	`full`	Full duplex when speed is forced (non-auto)
	`auto`	Auto negotiation of duplex mode (obsolete, but still supported in startup-config)
Default	All ports are set to Auto
Mode	Port List Interface mode
Usage	Use to set the duplex mode of the specified interface. To set duplex to the default, use the ‘no’ form of the command.
Example	Example 1: Set duplex for port 1 to half. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# duplex half`

This command configures the flow control for the interface (to slow packet transition temporarily upon request, or, for packet reception, to signal the remote transmitter to temporarily slow down its packet transition whenever switch reception buffer becomes to full). PFC and flowcontrol cannot both be enabled on the same port.

Command Syntax:

flowcontrol { on | off }
priority-flowcontrol prio <prio>

Table 3-21. Command Description
	Argument	Description
Parameter	`on`	Enable flowcontrol.
	`off`	Disable flowcontrol.
	`<prio>`	Range of priorities (for example, 0–4,7)
Default	All ports flow control receive and send is off. Priority flowcontrol is off
Mode	Port List Interface mode
Usage	Use to set the flow control and PFC for the interface. To revert to the default, use the ‘no’ form of the command.
Example	Example 1: Enable flowcontrol for port 1. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# flowcontrol on` Example 2: Enable priority flowcontrol with 0–3 priorities for all ports. `# configure terminal (config)# interface * (config-if)# priority-flowcontrol prio 0-3`

Use this command to specify maximum Ethernet frame size for the interface.

Command Syntax:

mtu <max_length>

Table 3-22. Command Description
	Argument	Description
Parameter	`<max_length>`	Maximum frame size in bytes. The range is 1518–10240 bytes.
Default	All ports mtu 10240 bytes
Mode	Port List Interface mode
Usage	Use to set the maximum frame size for the interface. To return to the default, use the ‘no’ form of the command.
Example	Example 1: Set mtu for port 1 to 1518. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# mtu 1518` Example 2: Set mtu for all ports to 1518. `# configure terminal (config)# interface * (config-if)# mtu 1518`

Use this command to configure port transmit collision behavior.

Command Syntax:

excessive-restart

Table 3-23. Command Description
	Argument	Description
Parameter	N.A	N.A
Default	Discard frame after 16 collisions
Mode	Port List Interface mode
Usage	Use to set the maximum frame size for the interface. To return to the default, use the ‘no’ form of the command.
Example	Example 1: Restart backoff algorithm after 16 collisions for port 1. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# excessive-restart` Example 2: Discard frame after 16 collisions for all ports. `# configure terminal (config)# interface * (config-if)# no excessive-restart`

This command configures if frames with incorrect frame length in the EtherType/Length field shall be dropped.

Command Syntax:

frame-length-check

Table 3-24. Command Description
	Argument	Description
Parameter	N.A	N.A
Default	None
Mode	Port List Interface mode
Usage	Drop frames with mismatch between EtherType/Length field and actual payload size. To disable the frame check, use the ‘no’ form of the command.
Example	Example 1: Disable frame length check for port 1. `# configure terminal (config)# interface GigabitEthernet 1/1 (config-if)# no frame-length-check` Example 2: Enable frame length check for all ports. `# configure terminal (config)# interface * (config-if)# frame-length-check`