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This chapter describes:
- The steps to toggle the Avici router switch fabric to support version 2.7 switch cards or version 3.0 switch cards
- The ability to take a fabric link down after a configurable number of fabric down events occur over a set period of time.
Introduction
Switch Fabric Version Support
The Avici router is architected such that the active portion of the switch fabric is incorporated into each routing module. Each routing module consists of a switch card coupled with one of several types of line interface cards. The switch card is common to all Avici router routing modules.
The initial release of the Avici router supports version 2.7 switch cards. Version 2.7 switch cards require switch fabric version 1.0.
The latest release of the switch card is version 3.0. Version 3.0 switch cards require switch fabric version 2.0.
Fabric version 1.0 does not support version 3.0 switch cards. If your Avici router is running fabric version 1.0, a version 3.0 switch card will not boot. If your Avici router is running fabric version 2.0, a version 2.7 switch card will not boot.
If you have a Avici router with both version 2.7 and version 3.0 switch cards, you can toggle the version of the switch fabric to support one version or the other - but not both.
Avici routers in live networks should never be populated with a mixture of version 2.7 and version 3.0 switch cards. To do so requires that one version of the cards be inactive - which is usually not permitted in a live network. However, this feature is very useful in a test environment.
Controlling Fabric Down Events
A link bounce is an established fabric link that goes into a down state followed by a re-establishing of the link. Persistent link bounce is undesirable in a fabric. Some events that cause a link down-event are:
- Module failure
- CRC error discovered on the fabric link
- An uncontrolled module reboot
IPriori supports a Heuristic Link Transition Filter (HLTF). HLTF allows you to set, for each fabric axis, the number of allowable down events that can occur within a time window, before the link is permanently taken down. There are six link axes: plus and minus x, y, and z. If the number of current link down-events match the threshold set for that link's axis type, within the set time period, the link will be brought down and stay down until you reset the heuristic for that link, or the server reboots.
IPriori also supports the enabling and disabling of HLTF globally across the Avici router.
Setting the Switch Fabric Version
In a test environment, you may wish to populate your Avici router with both 2.7 and 3.0 switch cards. Since the fabric version required by the two types of switch cards is not compatible, only one fabric version may be active at any time.
To ease the configuration tasks associated with testing the 3.0 switch card, you can toggle the switch fabric between fabric version 1.0 and fabric version 2.0.
WARNING If you set the switch fabric to version 1.0, (to support 2.7 switch cards), 3.0 switch cards are not recognized and will not boot.
If you set the switch fabric to version 2.0 (to support 3.0 switch cards), 2.7 switch cards are not recognized and will not boot.PROCEDURE: Use the following steps to toggle the version of the switch fabric:
Step 1 Use the configure terminal command to enter Configuration Command mode.
Step 2 Use the fabric-version 2.0 command to configure the fabric version.
Step 3 The Avici router reboots, and only those modules with a version 3.0 switch card are discovered by the bay controller and booted.
Step 4 Use the show fabric version command to display the configured fabric version.
In the following fabric-version command example:
- The show fabric version command displays the current fabric version.
- The fabric-version 2.0 command configures the fabric version as 2.0.
- A warning that currently operating modules will not reboot is displayed, and a prompt "Are you sure [yes|no]?" is displayed.
- A yes response reconfigures the fabric to Fabric version 2.0. The Avici router reboots, and only those modules with a version 3.0 or later switch card are discovered by the bay controller and booted.
Example: The show fabric version command displays the new setting:
router#show fabric version
Fabric Version: 1.0
Fabric Routing Protocol Version: 3
router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#fabric-version 2.0
You are changing the fabric version of the system to a version that is incompatible with the configured fabric version. Any modules that are currently operational will be rebooted and will not be allowed to boot.
Are you sure [yes|no]? yes
Changing fabric version...
Successfully reset module 1/1
Successfully reset module 1/5
.
.
.
router(config)#end
router#show fabric version
Fabric Version: 2.0
Fabric Routing Protocol Version: 3
CAUTION If the following error message is displayed:
Failed to reset module bay/slot
the specified module has the compatible switch card, but has failed to boot properly. Use the boot command in Module Configuration command mode to manually reset the module.Understanding the Fabric Down-event Threshold and Time-Window
The Heuristic Link Transition Filter determines whether a link should be taken down permanently based upon two values: the down-event threshold and the time-window period. The down-event threshold is the maximum number of down-events that can occur on a given link before the fabric link is permanently taken down. The time-window period has two functions: it first plays a role in how much time passes before a down-event is dropped from the current down-event queue and secondly if during any time-window period the down-event threshold for a given link is reached, the link is administratively brought down.
The down-event threshold default is set to 10. The time-window period default is set to 10 minutes.
Each time a down-event occurs it is time stamped and placed in the current down-event queue. For example, when the link first comes up, there are no down-events in the down-event queue. When a link down-event occurs, this event is time-stamped and placed in the down-event queue. Assuming the default time-window period of 10 minutes and no other down-events occur, at the end of 10 minutes the down-event is removed from the down-event queue which is once again empty. If during any 10 minute period, the number of down-events remaining in the current down-events queue should equal the down-events threshold, the link is administratively taken down.
Changing the Down-event Threshold
You can change the down-event threshold for all link axes or a specific axis for this module using the fabric link down-event command in module configuration mode. You specify whether the change affects a specific axis or all axes, as well as the new down-event threshold value.
NOTE It is strongly recommended that you do not change the down-event threshold default values unless you are certain you know what you are doing. The unnecessary taking down of too many links can result in lost system forwarding performance.
Example: The following example changes the down-event threshold value for the x-plus axis to 7 for module 1/5:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#module 1/5
router(config-module)#fabric link down-event xplus 7
router(config-module)#end
Changing the Time-window Period
You can change the time-window period for all axes or a specific axis for this module using the fabric link time-window command in module configuration mode. You specify whether the change affects a specific axis or all axes, as well as the new time-window period value.
NOTE It is strongly recommended that you do not change the time-window period default values unless you are certain you know what you are doing. The unnecessary taking down of too many links can result in lost system forwarding performance.
Example: The following example changes the time-window period value for all x-plus axes to 12 minutes for module 1/5:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#module 1/5
router(config-module)#fabric link time-window xplus 12
router(config-module)#end
Resetting a Down Fabric Link
A fabric link down due to the heuristic link transition filter can be reset using the fabric link heuristic reset command in privileged command mode. You can specify the affected module and axis for the link to be brought up. Entering the command without specifying a module affects all modules.
Example: The following example resets the x-plus axis for module 1/5:
router#fabric link heuristic reset module 1/5 xplus
router#
Disabling the Heuristic Link Transition Filter (HLTF)
If you do not want fabric links dynamically brought down using HLTF, you can disable HLTF using the fabric link heuristic shutdown command in configuration command mode. You can re-enable HLTF using the no option with this command.
Example: The following example disables the heuristic link transition filter for this Avici router:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#fabric link heuristic shutdown
router(config)#end
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Source
File Name: FABRICconfig.fm
HTML File Name: FABRICconfig.html
Last Updated: 05/30/02 at 13:54:41
Please email suggestions and comments to: doc@avici.com