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Frequent Contributor

switch capacity

I am currently administering cisco 3850's & 3750's in our environment. We are soon taking over an entity which has around 300 staff along with usual wireless connectivity & voice traffic. They currently all use old 3500 switches.

In wanting to right size the capacity and get proper performance for those new bunch of people/traffic, how do i determine what device or switch will be best to handle layer2 traffic? can existing buffer on my 3750 give an indication & what should i look for?

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Line speed means the port can maintain full speeds, even with an "infinite" sequence of packets, back-to-back.

Usually also means the packets can be minimum sized.

Also may mean, all the device ports can do that, concurrently.

View solution in original post

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VIP Expert

Unsure I understand your questions. You were looking to replace the new entity's 3500s with 3750s, or were hoping, by looking at some stats on your 3750s, to estimate the performance requirements of the new entity's switches?

I will say, first, comparing 3500s to 3750s isn't as straight forward as it otherwise might be. The latter offers more fabric bandwidth and higher Mpps (especially the 3750E/3750-X, effectively "wire-speed" capable), but the 3750 series' QoS, when enabled, allocates buffers, by default, much differently. So much so, the (3560/)3750 series (and I believe the [3650/]3850 series) tend to have QoS "issues", not seen on the 3500 series. (NB: many of these QoS issues can be "corrected" by configuration changes.)

As to looking at device stats, well the new entity might have totally different usage patterns then yours, and again, how the device's are configured (optimally, or possible not), could skew your analysis just looking at device stats. Further, truth be told, many of the "older" non-wire speed (for all ports) switches are more than adequate for user edge usage, assuming they are not still running at 10 Mbps.

(Many years ago, I was in a fortune 100 company "upgrading" from 4 Mbps token-ring to 10 Mbps Ethernet. I asked what "kind" of Ethernet, and was told shared hub. Well, I said, we'll be the last to convert - thank you very much. Which was good, because other departments "noticed" the network difference moving from 4 Mbps TR to 10 Mbps shared Ethernet. Yes, those "upgraded" saw a huge drop in network performance! Before getting back to us, they replaced the 10 Mbps hubs with 10 Mbps switches. After that, I "approved" our upgrade, which from the user perspective, users saw no network performance difference [i.e. from TR]. I mention this, because moving from 3500 to 3850, may not be seen, by users, as an improvement, and in some cases, might actually be seen as a loss.)
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Thanks.

The aim is to get some information from either the 3500 or 3750 to purchase new switches at access layer for replacement  in the new evironment.

Just wanted to get an idea on what should be looked at when deciding on these new switches for access layer. bandwidth wise the particular user base is not expected to go more than 150Mbps. but then it also then feeds up to the wan connections. so would need something that can't be a bottleneck between access & higher layers.

I have also heard of line speed, has the line speed changed with newer access switches & does it mean it is the full availability of port speed that a user is connected to. eg. user connected on a 1G speed.

 

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Cat 9200 /Cat 9300 is a good candidate to replace those models.

 

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Line speed means the port can maintain full speeds, even with an "infinite" sequence of packets, back-to-back.

Usually also means the packets can be minimum sized.

Also may mean, all the device ports can do that, concurrently.

View solution in original post

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VIP Mentor

3750 going to be the end of life soon, but I look forward to introducing Cat 9300 if you have a budget for Longer run and investment protection.

 

 

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