From: darbyweaver@yahoo.com
Date: Sat Jun 03 2006 - 01:28:32 ART
Hi Feras,
A very obscure topic to present one with... but since you asked.
With that said:
Look to the bootom of the posting, the command you really want is called "flowcontrol"
The caveat is that "flowcontrol" and mls cannot be enabled at the same time.
The other caveat is the one about the Fastethernet interface and the gigabit interfaces on the 3550, the Gig interfaces do both send and receive, while FastEthernet only receives pause frame.
Note: I included a reference from the CAT 5000 as well. - First thing I found.
The "show to know" are:
sh int flowcontrol
sh flowcontrol
Here are some options for the Pause Frame:
Using Flow-Control Keywords
Table 6-2 describes guidelines for using different configurations of the send and receive keywords with the set port flowcontrol command.
Table 6-2 Send and Receive Keyword Configurations
Configuration Description
send on
Enables a local port to send pause frames to a remote port. Use send on when a remote port is set to receive on or receive desired.
send off
Prevents a local port from sending pause frames to a remote port. Use send off when a remote port is set to receive off or receive desired.
send desired
Indicates preference to send pause frames, but autonegotiates flow control. You can use send desired when a remote port is set to receive on, receive off, or receive desired.
receive on
Enables a local port to process pause frames that a remote port sends. Use receive on when a remote port is set to send on or send desired.
receive off
Prevents a local port from processing pause frames. Use receive off when a remote port is set to send off or send desired.
receive desired
Indicates preference to process pause frames, but autonegotiates flow control. You can use receive desired when a remote port is set to send on, send off, or send desired.
=============================================================
flowcontrol
Use the flowcontrol interface configuration command to set the receive or send flow-control value for an interface. When flow control send is on for a device and it detects any congestion at its end, it notifies the link partner or the remote device of the congestion by sending a pause frame. When flow control receive is on for the remote device and it receives a pause frame, it stops sending any data packets. This prevents any loss of data packets during the congestion period.
Use the receive off and send off keywords to disable flow control.
flowcontrol {receive | send} {desired | off | on}
--------------------------------------------------------------------------------
Note On the Catalyst 3550 switch, Gigabit Ethernet ports can receive and send pause frames; Fast Ethernet ports can receive only pause frames. Therefore, for 10/100 ports, the send keyword is not available.
--------------------------------------------------------------------------------
Syntax Description
receive
Set whether the interface can receive flow-control packets from a remote device.
send
Set whether the interface can send flow-control packets to a remote device. This keyword is not available for 10/100 Mbps interfaces.
desired
When used with receive, allows an interface to operate with an attached device that is required to send flow-control packets or with an attached device that is not required to but can send flow-control packets.
When used with send, the interface sends flow-control packets to a remote device if the remote device supports it.
off
When used with receive, turns off an attached device's ability to send flow-control packets to an interface. When used with send, turns off the local port's ability to send flow-control packets to a remote device.
on
When used with receive, allows an interface to operate with an attached device that is required to send flow-control packets or with an attached device that is not required to but can send flow-control packets.
When used with send, the interface sends flow-control packets to a remote device if the remote device supports it.
Defaults
The defaults for Gigabit Ethernet interfaces are flowcontrol receive off and flowcontrol send desired. The defaults for Fast Ethernet interfaces are flowcontrol receive off and flowcontrol send off.
Command Modes
Interface configuration
Command History
Release Modification
12.1(4)EA1
This command was introduced.
Usage Guidelines
You must not configure both IEEE 802.3z flow control and quality of service (QoS) on a switch. Before configuring flow control on an interface, use the no mls qos global configuration command to disable QoS on the switch.
Note that when used with receive, the on and desired keywords have the same result.
--------------------------------------------------------------------------------
Note On the switch, 10/100/1000 Mbps and GBIC ports can receive and send pause frames; 10/100 Mbps ports can receive only pause frames. Therefore, for 10/100 ports, the conditions described in the next paragraphs are always send off.
--------------------------------------------------------------------------------
When you use the flowcontrol command to set a port to control traffic rates during congestion, you are setting flow control on a port to one of these conditions:
receive on and send on: Flow control operates in both directions; pause frames can be sent by both the local device and the remote device to show link congestion.
receive on and send desired: The port can receive pause frames and is able to send pause frames if the attached device supports it.
receive on and send off: The port cannot send out pause frames, but can operate with an attached device that is required to or is able to send pause frames; the port is able to receive pause frames.
receive off and send on: The port sends pause frames if the remote device supports it, but cannot receive pause frames from the remote device.
receive off and send desired: The port cannot receive pause frames, but can send pause frames if the attached device supports it.
receive off and send off: Flow control does not operate in either direction. In case of congestion, no indication is given to the link partner and no pause frames are sent or received by either device.
Table 2-4 shows the flow control results on local and remote ports for a combination of settings. The table assumes that receive desired has the same results as using the receive on keywords. Because 10/100 Mbps ports cannot send pause frames, only the last two rows (send off) apply to these ports.
Table 2-4 Flow Control Settings and Local and Remote Port Flow Control Resolution
Flow Control Settings Flow Control Resolution
Local Device Remote Device Local Device Remote Device
send on/receive on
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Sends and receives
Does not send or receive
Sends and receives
Does not send or receive
Sends and receives
Does not send or receive
Sends and receives
Does not send or receive
Sends and receives
Does not send or receive
Receives only
Does not send or receive
send on/receive off
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Does not send or receive
Does not send or receive
Sends only
Does not send or receive
Sends only
Does not send or receive
Does not send or receive
Does not send or receive
Receives only
Does not send or receive
Receives only
Does not send or receive
send desired/receive on
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Sends and receives
Receives only
Sends and receives
Receives only
Sends and receives
Does not send or receive
Sends and receives
Sends only
Sends and receives
Sends only
Receives only
Does not send or receive
send desired/receive off
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Does not send or receive
Does not send or receive
Sends only
Does not send or receive
Sends only
Does not send or receive
Does not send or receive
Does not send or receive
Receives only
Does not send or receive
Receives only
Does not send or receive
send off/receive on
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Receives only
Receives only
Receives only
Receives only
Receives only
Does not send or receive
Sends and receives
Sends only
Sends and receives
Sends only
Receives only
Does not send or receive
send off/receive off
send on/receive on
send on/receive off
send desired/receive on
send desired/receive off
send off/receive on
send off/receive off
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Does not send or receive
Examples
This example shows how to configure the local port to not support any level of flow control by the remote port:
Switch(config-if)# flowcontrol receive off
Switch(config-if)# flowcontrol send off
You can verify your settings by entering the show interfaces privileged EXEC command.
Related Commands
Command Description
show interfaces flowcontrol
Displays interface input and output flow control settings and status.
show flowcontrol
Displays flow control settings and status for specified interfaces or all interfaces on the switch.
This archive was generated by hypermail 2.1.4 : Sat Jul 01 2006 - 07:57:31 ART