Conference irocz::common_brouters

738.0. "Hash Multiplier for VNswitch v1.1" by IROCZ::STETSON () Sun Feb 02 1997 19:52

Maintenance of the VNswitch Hash Multiplier in the CLI
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The hash multiplier is an input to the programmable randomizer function 
that is used by the hardware lookup engine when looking up the address 
and protocol fields within an input packet.  In most cases, the user should 
not find it necessary to modify the hash multiplier from the default value.  
However, in the v1.1 firmware release, it is remotely possible that 
the system could learn an address which results in an 
unresolvable collision.  In a subsequent firmware release this condition 
will be properly handled by the system.  In the v1.1 firmware release,
if such a collision occurs a console message will be displayed:

	'hash resolution shifted into hi'

At this point the user will be able to select a new hash multiplier at random
in order to remedy the collision.

The following describes the commands necessary to manage the Hash Multiplier 
from within the CLI on the v1.1 firmware release. These commands are added 
to the config process under bridging (CONFIG, PROTOCOL BRIDGE).

SET HASH-MULTIPLIER <value>
	
	Accepts a new multiplier value and saves it in non-volatile memory.
	<value> is the new multiplier value in the form of a 12 hex digit
	value. If the multiplier that is entered is incorrect, that is it
	does not conform to the correct format of 12 hex digits, 
	there will be a warning message, however the value that is entered
	by the user will be saved anyways.

	The user is reminded that it is necessary to restart the module
	for the new multiplier to take effect.

DELETE HASH-MULTIPLIER

	Deletes the hash multiplier that is currently stored in non-volatile
	memory and restores the default multiplier value. 

	The user is reminded that it is necessary to restart the module
	for the new multiplier to take effect.

LIST HASH-MULTIPLIER

	Displays the following information:
		current effective hash multiplier that was loaded at 
			initialization and note how it was obtained
		number of unresolved collisions, that is, the number of entries 
			that could not be added to the hardware lookup 
			engine due to the inability to resolve collisions 
			with other entries. 
		number of times an automatic rehash has occurred.  (Since
			an automatic rehash causes a restart to occur, this 
			counter is non-volatile.)

	The user is warned if a hash multiplier has been set in NV but is 
	not current because a restart is required.

	Example display:
		Current Hash Multiplier			: 55aa11223344
		(Set by the User)
		Number of Unresolved Collisions		: 0
		Number of Rehashes			: 0