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New Member

Sup IV - QoS Sharing


I am in the process of designing a network that involves Dual 4506 Switches in the core and have a question that should finally help me choose the Sup IV over the V.

In the matrix table that compares them both it says that the SupV supports QoS Sharing but the Sup IV does not. What is QoS sharing, I cant seem to find any information on it?

The client will be running Cisco IPT across the network and as such AutoQoS will be configured.

I want to go for the IV as the price hike for the V does not seem worth it for the other differences.


New Member

Re: Sup IV - QoS Sharing

If you're planning on running a lot of ports with the same qos policy then you should look at per-vlan QoS over per-port QoS.

This drops the TCAM and input/output policer use dramatically. I've done this recently for one customer with 5 * 48 ports w/ Sup4 and freed up over 90% of the policer/QoS TCAM use.

But then, you've mentioned you're running Cat4506's in the core, which implies they're not connected to end-users. Please elaborate a little more on the network design and I'll let you know what to look for.


New Member

Re: Sup IV - QoS Sharing

Hi Adrian,

So from your post I take it QoS sharing provides the ability to apply a QoS policy to a VLAN which in turn gets placed on all ports associated with that VLAN ?

I am planning on running the 4506 switches as core devices that connect to several 3750 stacks for user connectivity. There will be only be AutoQoS Trust DSCP commands entered onto the 4 or 5 Gigabit ports that connect with the 3750's.

New Member

Re: Sup IV - QoS Sharing

YEs, the idea with the per-vlan QoS is:

* you apply the QoS to the VLAN SVI (int VlanXXX)

* You then configure each port to use per-vlan QoS (qos per-vlan or something similar) so the policies get applied per-port but share the same resources (policers, tcam)

If you're using autoqos trust on five gigabit ports on a 4506 - and not modifying the default autoqos configuration at all - then a Sup4 will be fine. You won't even need per-vlan QoS. But if you're running 4 * 48 ports with QoS policies (as if you're using a 4506 as the edge switch) then you might need per-vlan QoS. :P

Let me know if you'd like to find out more about the Catalyst 4500 QoS and resource management - there's a few bookmarked Cisco site links I have which cover these topics.

New Member

Re: Sup IV - QoS Sharing

Also, hm, could you please post a link or description about "QoS Sharing"? I Just want to be sure I know what you're talking about.

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