142 BigIron RX Series Configuration Guide53-1001986-01Disabling or re-enabling flow control6• auto-gig – The port tries to performs a negotiation with its peer port to exchange capabilityinformation. This is the default state.• neg-off – The port does not try to perform a negotiation with its peer port.Unless the ports at both ends of a Gigabit Ethernet link use the same mode (either auto-gig orneg-off), the ports cannot establish a link. An administrator must intervene to manually configureone or both sides of the link to enable the ports to establish the link.Changing the negotiation modeTo change the mode for individual ports, enter commands such as the following.BigIron RX(config)# int ethernet 4/1 to 4/4BigIron RX(config-mif-4/1-4/4)# gig-default neg-offThis command changes the default auto-gig setting and sets the negotiation mode to neg-off forports 4/1 – 4/4.Syntax: gig-default neg-full-auto | auto-gig | neg-offDefault is gig-default auto-gigThe neg-full-auto, auto-gig, and neg-off options are as described above.Disabling or re-enabling flow controlYou can configure full-duplex ports on a system to operate with or without flow control (802.3x).Flow control is enabled by default.To disable flow control on full-duplex ports on a system, enter the following.BigIron RX(config)# no flow-controlTo turn the feature back on.BigIron RX(config)# flow-controlSyntax: [no] flow-controlSpecifying threshold values for flow controlThe 802.3x flow control specification provides a method for slowing traffic from a sender when aport is receiving more traffic than it can handle. Specifically, the receiving device can send out802.3x PAUSE frames that request that the sender stop sending traffic for a period of time.The device generates 802.3x PAUSE frames when the number of buffers available to a module'sBuffer Manager (BM) drops below a threshold value. A module's BM can start running out ofbuffers when a port receives more traffic than it can handle. In addition, the device drops thelowest priority traffic when the number of available buffers drops below a second threshold. Whenthe number of available buffers returns to a higher level, the device sends out another PAUSEframe that tells the sender to resume sending traffic normally. You can specify values for boththresholds, as well as the module where the thresholds are to take effect.
