[afnog] How to dedicate bandwith betwen 2 ports on the same switch ?

[Mark Tinka]

On Tuesday 13 January 2009 02:49:07 am Meuyou Noumba wrote:

> Im using a cisco catalyst 2950. How can I do that??

Because the Cisco Catalyst family of switches typically 
forward Ethernet frames in hardware (as well as IP packets, 
with a couple of restrictions to note particularly on the 
smaller, desktop models), the QoS features available to the 
various ranges of products in this line vary greatly.

Even for the larger models (like the 6500 series switch), 
some features depend on what type of line card is installed 
and/or what type of supervisor engine is running.

It also matters how late your IOS version is, as well as 
whether you're running a Standard or Enhance image for the 
desktop switches, e.g., the 2950 as in your case.

About the issue you face, I'd recommend spending some time 
on the QoS FAQ for the 2950 first:

http://www.cisco.com/en/US/tech/tk389/tk813/technologies_q_and_a_item09186a00804976d3.shtml

What you're trying to achieve is a rate limiting situation 
based on destination interface. 

I don't have a 2950 switch handy, but even on the 3560G 
switch I'm looking at (which has a more advanced QoS feature 
set than the 2950), I can only have an input interface as a 
match condition. What you need is an output interface to 
match all traffic destined for the port the other server is 
on.

CAR (Committed Access Rate), which is an older rate limiting 
technology, is only supported on the 3750-METRO switch for 
the desktop switch type, so that's not an option.

You could also match on destination VLAN but this switch 
doesn't support that.

Based on the QoS capabilities I can find for this hardware, 
I'd recommend policing on inbound with a match condition 
constituting an IP ACL, where the IP address of the server 
on the other port is specified as the source. You can then 
define an action to police traffic to 500Mbps, and replicate 
the same configuration for the other port.

You would need the EI image for this, though.

Hope this helps.

Cheers,

Mark.
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