On 26/07/2011 21:47, Geert Nijs wrote:
On tip i have is also the following: although the C3750E switch is a 'shared bufffer switch', each ASIC does have memory on-board. Normally 4 GE ports are using 1 ASIC. (you can see the mapping with "sh platform pm port-asic" or something like that).
I spent a long time looking one day, and eventually found the following URL:
http://www.cisco.com/en/US/docs/solutions/Enterprise/Video/tpqoscampus.html#wp1062179
"Additionally, these platforms provide (minimally) 750 KB of receive buffers and (up to) 2 MB of transmit buffers for each set of 4 ports."
So, this indicates that there is a shared buffer pool per ASIC with <= 2M transmit buffers for egress traffic. As this is a store-n-forward switch, this is really very little. And as pointed out before, if you enable "mls qos" the default setting is to carve this up into 4, leaving you with a default of <= 512k for class-default per 4 ports. Little wonder people drop packets on these boxes!
It would help if Cisco were more forthcoming about their switch buffer sizes. Unfortunately, the received wisdom is: "if you have to ask, the buffers are too small for your requirements".
Other vendors (Juniper, Brocade, etc) are much more up-front about their kit's capabilities in this regard.
Nick _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
