Can I set port speed to 20mbps somehow?

keithsauer507 · ‎03-26-2014

Hi, we have a WAN to another location which goes out a switchport on a 3750 to our communication providers equipment (they are handing this off from an ME3400).

We are adding a second (new) location and using the same provider. They said that ok, you have 20 megs now coming into your HQ, and 10 goes to site 1 and 10 goes to site 2. Well they didn't come out and install anything new at the HQ. They said it comes over the same conneciton we already have.

Ok well we currently have speed 10 on this link, but if you would try to do speed 20 its not valid. I found this thread here: http://www.techrepublic.com/blog/data-center/limit-bandwidth-on-a-cisco-catalyst-switch-port/#. This has to do with using the command srr-queue bandwidth, but the thing is I see some contradicting comments in this article.

So is that the proper way to limit the speed so our ISP doesn't drop packets? I don't know why they just don't do the speed settings on their end... I mean if you get an internet connection that is 20 megs and upgrade it to 50 megs, you don't have to do anything on the switchport / router / cpe connected to that device.

Vasilii Mikhailovskii · ‎03-26-2014

Hello.

There is no way to limit traffic on sub-rate (20M on 100M link) without router.

Surely you are a customer and for configuration simplification (if you don't need full-mesh for your WAN), you may ask ISP to provide you 2*10M ports at HQ.

Joseph W. Doherty · ‎03-27-2014

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Posting

BTW, many Cisco L3 switch do support some form of policing and/or shaping, especially the Metro series switches. I.e. a router isn't always necessary to limit traffic to some sub rate.

keithsauer507 · ‎03-27-2014

Ok well we have a spare 2811 router I think we will use for this. Why not, its sitting in our rack doing nothing, might as well use it. It used to be our internet router but we moved that over to load balancers when we added an additional ISP.

Joseph W. Doherty · ‎03-27-2014

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A 2811 does have a much "richer" QoS feature set than a 3750. However, in my experience, 20 Mbps, duplex, is about the maximum capacity of a 2811. I.e. it might be suitable, or it might not.

Leo Laohoo · ‎03-26-2014

Depends on the model of your appliance (router or switch) you can enable Traffic Shaping.

Joseph W. Doherty · ‎03-27-2014

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

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If your HQ link is physically only 10 Mbps, and your remotes each 10 Mbps, that's certainly possible. However, altough you have 20 Mbps comming into your provider at your HQ, if, again, your link to them, at the HQ, is just 10 Mbps, then you really don't have 20 Mbps coming to you.

Often in situations like yours, the physical "hand-off" at your HQ might be 100 Mbps, but the provider will limit your maximum bandwidth to some lower (agreed upon - paid for) rate. For example, your HQ link might be configured to drop traffic, from your HQ, in excess of 20 Mbps.

In situations like what I just described, you might want to limit your tranmission rate to no more than 10 Mbps being directed to each remote, allowing you to control traffic priorization and drop priorization. That could be accomplished on a 3750 by directing all traffic to the same remote to one of the four possible egress queues and shaping that queue.

keithsauer507 · ‎03-31-2014

Well we moved this to a spare 2811 router. We are getting the full 20mbps to one site at a time, or if we transfer data to both sites at the same time both transfers equalize to around 10mbps.

We are only supposed to have 10meg to each site, but we get 20 so the ISP must have goofed. They also had an MTU issue so we could never do q-in-q vlan tunneling over the WAN. They fixed that so we think tonight we are going to change things a bit. They had to add our new site to the same "switching domain" but encouraged us to go vlan for future locations that may not be able to be put in the same switching domain.

The remote sites have 2911 routers and they are limiting outbound to the HQ at 10mbps. So each site can send to the HQ at 10meg, and if both sites saturate the link, we see 20 meg coming in and were not getting squashed. I just find it interesting if all pipes are clear, we can push over 10 meg to one site, meaning the ISP misconfigured us in our favor (for once).