HP Cisco Nexus 5000 Cisco MDS 9000 Family CLI Configuration Guide - Release 4. - Page 360

Buffer Credits Chapter 13 Configuring Interfaces Send documentation comments to [email protected] Manually Inserting Entries into ALPA Cache To manually insert entries into the ALPA cache, follow these steps: Step 1 Step 2 Step 3 Command Purpose switch# config t Enters configuration mode. switch(config)# tlport alpa-cache interface Configures manual entries into the ALPA cache. fc1/2 pwwn 22:00:00:20:37:46:09:bd alpa 0x02 switch(config)# tlport alpa-cache interface Removes this entry from the ALPA cache. fc1/3 pwwn 22:00:00:20:37:46:09:bd Displaying the ALPA Cache Contents The show tlport alpa-cache command displays the contents of the ALPA cache. switch# show tlport alpa-cache alpa pWWN Interface 0x02 22:00:00:20:37:46:09:bd fc1/2 0x04 23:00:00:20:37:46:09:bd fc1/2 The first entry indicates that if a device with a pWWN of 22:00:00:20:37:46:09:bd is exported on TL port fc1/2, then the pWWN is allocated an alpa 0x02 (if available). Clearing the ALPA Cache The clear tlport alpa-cache command clears the entire content of the ALPA cache. Buffer Credits Fibre Channel interfaces use buffer credits to ensure all packets are delivered to their destination. This section describes the different buffer credits available on the Cisco MDS Family switches and includes the following topics: • About Buffer-to-Buffer Credits, page 13-34 • Configuring Buffer-to-Buffer Credits, page 13-35 • About Performance Buffers, page 13-36 • Configuring Performance Buffers, page 13-36 • About Extended BB_credits, page 13-36 • Configuring Extended BB_credits, page 13-38 • Displaying BB_Credit Information, page 13-39 About Buffer-to-Buffer Credits Buffer-to-buffer credits (BB_credits) are a flow control mechanism to ensure that FC switches do not run out of buffers, because switches must not drop frames. BB_credits are negotiated on a per-hop basis. 13-34 Cisco MDS 9000 Family CLI Configuration Guide OL-18084-01, Cisco MDS NX-OS Release 4.x