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Community Member

C3750G QoS

Dear All,

I have two sites connected using 600Mbps (CIR) terminated as a fiber link provided by the service provider. The WAN devices are C3750G, IPS image. So one C3750G is in site-A (C3750G-A) and one C3750G in site-B (C3750G-B).

From the LAN side I have two separate networks (LAN-1 and LAN-2) in site A and two separate networks in site B (LAN-1 and LAN-2), so I already configured VRF-lite for this on the WAN by configuring the WAN link is a trunk with two VLANs and terminated the two VLANs in to two SVIs, and two VRFs is configured.

The LAN-1 in site A can speak to LAN-1 in siteB, LAN-2 in site A can speak to LAn-2 in site B.

The problem is that LAN-1 contains corporate users that are consuming the bandwidth between the two sites so I want to rate limit the traffic between LAN-1 in the two sites to 100Mbps and leave the remaining bandwidth for LAN-2. On the other hand in LAN-2 I have video, audio and FTP and I want to give high priority for the video and audio.

So what is the best QoS for this scenario? I have good understanding of QoS MQC. But I read in the manual that C3750 support another features like mls qos. So can I use MQC or I have to use “mls qos” configurations? Please advice?

Thanks

Anas

4 REPLIES
Super Bronze

Re: C3750G QoS

You'll need to use the MLS QoS featurs.

What I suggest is setting your "WAN" with "srr-queue bandwidth limit 60" (you might need to decrease value, it's not exact), place real-time traffic (regardless of VRF) into an Egress Expedite Queue (see "priority-queue out" command), determine how best to utilize the remaining 3 egress queues in shared mode.

Generally, I only recommend rate limiting as a last resort. I prefer to assign bandwidth ratios to different traffic types. This so various traffic types have a guaranteed mimimum amount of bandwidth but can utilize otherwise unused bandwidth.

In your description, rather than limit LAN-1 to 100 Mbps, you could define its queue as 1/6 of total bandwidth allocation. LAN-2 would be defined for 5/6 of total. (How you account for the expedite queue's bandwidth depends on how you want share it. If only LAN-2 uses it, you might account for its bandwidth as part of the 5/6.)

Another way you might allocate bandwidth, which I suggest, forget about LAN number and allocate per traffic type. All real time traffic would be placed into the expedite queue. The remaining 3 queues might allocate bandwidth for better than BE, BE and less than BE.

You could also mix and match these two approaches. For example, you might have two queues, one dedicated per LAN-#, one queue (again) for real-time, and the 4th queue for some really critical or really bandwidth consuming traffic taking into account LAN-# or not. Assign bandwidth ratios as desired.

BTW, you can also "shape" the rate of one or more queues, and police traffic, but again, I suggest utilization of all available bandwidth.

Details of the MLS QoS commands can be found in the reference and configuration guides for your IOS.

Community Member

Re: C3750G QoS

Thank you,

so you mean if i configure mls qos in the outbound WAN interface it will effect all configured VRFs.?

i noticed that there are class-map and policy-map commands supported in the 3750 switch but with limited match (match access-group) so do you think i can configure MQC?

Thanks again.

Super Bronze

Re: C3750G QoS

"so you mean if i configure mls qos in the outbound WAN interface it will effect all configured VRFs.? "

I think that's the case.

"i noticed that there are class-map and policy-map commands supported in the 3750 switch but with limited match (match access-group) so do you think i can configure MQC? "

Not as you want to use it for egress, although the Metro 3750 might.

Community Member

Re: C3750G QoS

Hi, I beleive that the best QoS scenario would be to use LLQ on the links between your two C3750, and for the policing on the LLQ to start policing your need to set the "mpls qos vlan based command" on the port that has the wan link.

Sincerely,

Francisco

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