11-12-2004 11:03 AM - edited 03-13-2019 07:00 AM
Does anyone know if Stacking more then two switches together using the Half-Duplex GigaStack Cascade Configuration causes an issue with the QoS in a VoIp environment. If so can you point me to some documentation?
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11-12-2004 11:08 AM
It does - basically if you run a show interface gig 0/whatever your gigastack is plugged into, you will see that it is running in half duplex mode.
If you only have a single cable to each GBIC (in a star config) it will go to full-duplex.
Anything that runs half-duplex will have collisions and performance will tail off as it gets more heavily utilised... so QoS can't be guaranteed - even if packets are scheduled correctly out of the port they may be wiped out by a collision.
Go to
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns17/c649/ccmigration_09186a00800d67ed.pdf
In this QOS reference guide there is a non-favourable mention of Gigastacks...
11-12-2004 11:08 AM
It does - basically if you run a show interface gig 0/whatever your gigastack is plugged into, you will see that it is running in half duplex mode.
If you only have a single cable to each GBIC (in a star config) it will go to full-duplex.
Anything that runs half-duplex will have collisions and performance will tail off as it gets more heavily utilised... so QoS can't be guaranteed - even if packets are scheduled correctly out of the port they may be wiped out by a collision.
Go to
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns17/c649/ccmigration_09186a00800d67ed.pdf
In this QOS reference guide there is a non-favourable mention of Gigastacks...
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