Changing switching mode on Catalyst 2900-3500 Series

[josegp]

Hello,

Exist a way to change a Catalyst switch 2900-3500 Series to Store-and-forward or Cut-through switching mode using the command line or this parameter is fixed and cannot be changed on this switchs models?

Thanks,

Jose

[milan.kulik]

Hi,

AFAIK, Cat2900-3500s support only store-and-forward.

See

"Note The switch supports the store-and-forward switching mode. Store-and-forward mode stores complete packets and checks for errors before transmission. It is the most error-free form of switching. "

in http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35wc6/scg/swports.htm

and http://www.cisco.com/warp/public/cc/pd/si/casi/ca3500xl/tech/c3500_wp.pdf

for 3500 architecture description.

Regards,

Milan

[robho]

Hi,

Those switches only support store and forward. This is to avoid forwarding bad frames through the switch.

-Robert

[ahojmark]

Cut-Through doesn't really make sense on switches that run ports at different speeds.

For example, if traffic is forwarded from a GE uplink to a user port running 10 Mbps, the switch would need to buffer the data anyway, essentially becoming a store-and-forward switch. And if traffic was sent the other way in a cut-through fashion, you'd need to slow down the uplink (which you can't really do, as soon as you've started clocking a packet onto the port).

You could in theory do cut-through between ports running at the same speed and store-and-forward between other ports, but as soon as you'd start mixing traffic (as you will on a LAN), that wouldn't work either.

So, in practice, all switches are store-and-forward today. (And, with FE, GE and 10G, the latency is so low anyway, that it doesn't really matter).

-A