Unusual QoS Issue on cisco 3750s

Posted on 2009-04-23
Medium Priority
Last Modified: 2012-06-27
We are having a problem implementing QoS on our cisco kit and I would be grateful if anyone can suggest a suitable low cost solution to this issue. The problem is as follows: We use cisco 3750s in our remote sites which connect via 2mb leased lines to a couple of 3750s in our main site. Instead of using routers we use the Paradyne Network extender kit (These basically allow the switches to talk to each other as if they were directly connected) The problem is that we cannot tell QoS to only use 2mb of the 100mb ports on the 3750. The problem is that 10 % is the lowest you can define using the srr-queue bandwidth limit command. This would obviously utilise 10mb but  as far as the switch is concerned there is no congestion so QoS never kicks in even though the physical link can only hande 2mb. One way we tried to get around this was setting the speed of the 100mb interface to 10mb and using the following config to tell QoS that only 20% of the interface speed should be used: srr-queue bandwidth limit 20.   We then found that the Paradynes can only negotiate 10mb half-duplex so this option was no good. At our core site we could use an extra switch which would sit between the network extenders and the current switch. We could then negotiate 10mb full duplex between the two switches allowing QoS to work and could negotiate 100mb full duplex between the new switch and the Network Extenders. However this is not cost effective for our remote offices unless anyone knows of a 4 port switch that can have its speed and duplex settings fixed rather than left to auto-negotiate. If anyone can suggest something we are missing it would be greatly appreciated!
Question by:systems_mitsui
  • 2
LVL 32

Expert Comment

ID: 24216305

What model 3750? Metro does CAR. (rate-limit command)

harbor235 ;}

Author Comment

ID: 24222386
They are IPServices. Unfortunately CAR is not available.
LVL 32

Accepted Solution

harbor235 earned 2000 total points
ID: 24224319

aah, thats why I asked if you had the 3750 METRO, it does have CAR, it's the only one in the 3750 series.

How about "mls qos aggregate-policer " command does your model have that?

Which model do you have exactly and with what image?

harbor235 ;}


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