WAAS NIC Teaming

Unanswered Question
Aug 4th, 2009


I have question regarding WAE NIC teaming. The decision to switch between members of standby interfaces is based on the following three parameters:

1. Inteface status (up/down)

2. If the interface is up, is the default gateway pingable (yes/no)

3. Number of interface level errors (collisions, overruns, etc) higher than

the configured threshold or not.

How much time does it take for switchover in each of the three cases?



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Zach Seils Wed, 08/05/2009 - 12:07


The interface state and error counts (when configured) are checked once every 10 seconds. For (2), an ICMP echo request is sent once every 10 seconds to the configured default gateway. If there is a response to the echo request, the interface is considered up. If there is no response to the echo request, five more echo requests are sent. If at least three responses are received, the interface is considered up. Otherwise, the interface is considered failed, and the interface is marked as down.

Note that this behavior was changed in WAAS 4.1. Note the following new behavior:

The failure of the active interface in the standby group is detected by monitoring the link state of the active interface. Line protocol is up when the RUNNING flag is present on the Ethernet interface. If line protocol fails on the active interface, the interface is marked as down.

The interface state is checked once every 100 milliseconds. If the active link fails, the next available interface is activated. When the primary interface recovers, it becomes the active interface for the group.



nsyal Wed, 08/05/2009 - 20:50


1) Incase of pre 4.1 releases, if the link protocol goes down, it can take upto 10 seconds to detect it and to do a switchover. This interval is changed to 100ms in 4.1 release. Is my understanding correct? Also during this time, what happens to the existing and new connections?

2) Incase of (2), i.e ICMP ping to default gateway, if the gateway has failed, it can take upto 60 seconds to detect it and switchover. Will this not interrupt traffic for such a long time?



Zach Seils Fri, 08/07/2009 - 13:34


In response to your questions:

1. Yes, this is correct. Existing connections should be unaffected during this time.

2. It's possible that a 60 second delay could cause some connections to time out.




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