configure forwarding hash-algorithm

configure forwarding hash-algorithm [crc16 | crc32]

Description

Modifies hardware table utilization by configuring the hash algorithm or dual-hash settings.

Syntax Description

crc16 Specifies the CRC16 hash algorithm.
crc32 Specifies the CRC32 hash algorithm. This is the default setting.
on Specifies that the dual-hash feature be turned on for the L3 Hash Table for hardware with dual-hash capability. With dual-hash on, each hash bucket is divided into two half-buckets with independent hash algorithms. One half-bucket uses the configured hash algorithm (CRC16 or CRC32), and the other half-bucket uses an alternate hash algorithm. This is the default setting. The “dual-hash” function applies only to the BlackDiamond 8800 series switches.
off Specifies that the dual-hash feature be turned off, even for hardware with dual-hash capability. The “dual-hash” function applies only to the BlackDiamond 8800 series switches.

Default

In ExtremeXOS 11.5, the default hash algorithm is crc32.

In ExtremeXOS 11.4 and earlier, the default hash algorithm is crc16.

The dual-hash default is “on.”

Usage Guidelines

Note

Note

Modify the hardware table hash algorithm only with the guidance of Extreme Networks technical personnel.

The switch uses a hash algorithm to decide where to store the addresses in the hardware table. The standard, default hash algorithm works well for most systems; however, for some addresses with certain patterns, the hardware may attempt to store address information in the same section of the hardware.

If you are running ExtremeXOS 11.4 or earlier and experience a full hardware table that affects Layer 2, IP local host, and IP multicast forwarding, you see messages similar to the following in the log:

 <Info:HAL.IPv4Adj.Info> : adj 136.159.188.109: IP add error is Table full for new or newly resolved ARP, egress valid <Info:HAL.IPv4Adj.Info> : adj 136.159.188.109: returned -17 for L3 table bucket 181 <Warn:HAL.IPv4Mc.Warning> : Could not allocate a hardware S,G,V entry (889f4648,effffffa,70) - hardware table resource exceeded (rv=-17). 

If you are running ExtremeXOS 11.5 or later and experience a full hardware table that affects Layer 2, IP local host, and IP multicast forwarding, you see messages similar to the following in the log:

 <HAL.IPv4Adj.L3TblFull> MSM-A: IPv4 unicast entry not added. Hardware L3 Table full. 

(ExtremeXOS 12.1 and later have the Extended IPv4 Host Cache feature and do not display this HAL.IPv4Adj.L3TblFull message on the MSM for a full hash table condition.)

<Card.IPv4Adj.Warning> Slot 4: IPv4 unicast entry not added.  Hardware L3 Table full.
<HAL.IPv4Mc.GrpTblFullEnt> MSM-A: IPv4 multicast entry (10.0.0.1,224.1.1.1,vlan 1) not added.  Hardware Group Table full.
<Card.IPv4Mc.Warning> Slot-4: IPv4 multicast entry not added.  Hardware L3 Table full.

In the previously described situations, you can configure a different hash algorithm to select a different section of the hardware to store addresses. You must save your configuration and reboot the switch to modify the hash algorithm used by the hardware table. Typically, the dual-hash feature improves hash utilization. You must save your configuration and reboot the switch to turn dual-hash on or off.

Upgrading to ExtremeXOS 11.5

When you upgrade to ExtremeXOS 11.5, the hash algorithm automatically becomes crc32. For example, if you saved a configuration using an image from ExtremeXOS 11.4 or earlier with the hash algorithm set to crc16, when ExtremeXOS 11.5 loads, the hash algorithm becomes crc32. To change the hash algorithm to crc16, use the configure forwarding hash-algorithm crc16 and save your switch configuration.

Example

The following example modifies the hardware table hash algorithm to crc16:

configure forwarding hash-algorithm crc16

The switch displays the following message to describe the change and to prompt you to save your configuration and reboot the switch:

Configured hash alorithm has been changed to ?crc16‘ with L3 dual-hash support ?on‘ for applicable HW.
Warning:  This command will only take effect after a save and reboot

The following example disables dual-hashing on BlackDiamond 8000 c- and xl-series I/O modules.

configure forwarding hash-algorithm crc32 dual-hash off

The switch displays the following message:

Configured hash algorithm has been changed to ?crc32‘ with L3 dual-hash support ?off‘ for applicable HW.
Warning: This command will only take effect after a save and reboot.

To display the results, use the show forwarding configuration command.

History

This command was first available in ExtremeXOS 11.3.2.

The default hash algorithm was changed to crc32 in ExtremeXOS 11.5.

Platform Availability

This command is available only on all platforms.