CISCO WS-C3750G-12S-E Routing capabilities

[perpaal]

Hi

I have 2 CISCO WS-C3750G-12S-E witch I`m concidering using as redundant VLAN routers for a small WISP network.

Do not have much experiences with these, so I might be asking stupid questions...

The network has about 2000 connected clients.

Traffic is about 300 - 400 Mbps duplex.

100000 -  150000 PPS

Expected this to get to about 3000  connected clients.

Traffic about 500 - 700 Mbps duplex.

150000 -  200000 PPS

Before these end their duty

Are they up for the task, or do you reccomed something different?

[paolo bevilacqua · Accepted solution]

It's an easy job for the 3750. They support up to 12K MAC entries.

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5023/product_data_sheet0900aecd80371991.html

[perpaal]

Thank you for quick reply.

But what about CPU, raw power.

Can it handle the traffic, and PPS.

No problem at all?

[Jon Marshall]

It's all in the link Paolo gave. Have a look at Table 2, the first bit about performance.

The short answer is yes, with a 32Gbps switch fabric and a forwarding capability of 17.8 million packets per second for the model you quote it will be fine.

Jon

[paolo bevilacqua]

I never recommend anything unless it's 100% recommendable.

Thank you for the nice rating and good luck!

[perpaal]

But are not these numbers just for switching?

Routing will be a different animal, much more CPU intensive right?

(Now worry, always very glad and greatfull to get help, and will rate all usefull posts at the end)

[Jon Marshall · Accepted solution]

Routing on L3 switches is done in hardware not software ie. it is switched traffic, just L3 switched rather than L2.

Jon

[perpaal]

Ok, thanks.

I`m using these then

[paolo bevilacqua]

No problem. But try to be more trustful of brand name products and expert advice.

Thanks for the nice rating and good luck!

[Joseph W. Doherty · Accepted solution]

Disclaimer

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.

Liability Disclaimer

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.

Posting

As the others have stated, for what you've described, your 3750 should be fine.

A couple of additional pointers.  Jon is 99.999% correct that L3 switching is done in hardware, i.e. L2 and L3 both have the same PPS forwarding rate.  Sometimes, fortunately very rarely with later L3 switches, certain L3 packets will not be hardware switched but forwarded by the switches software, much, much, much slower.  As far as I know, this doesn't happen for L2.

e.g. (3750 Q&A)

Q. What types of packets are not hardware-forwarded?

A. The Cisco Catalyst 3750 Series Switches will completely  hardware-forward only IPv4 packets with no options set in Ethernet II  encapsulation. This includes bridging, routing, security, and QoS  lookups. Packets that do not conform to all three criteria will be  forwarded using a combination of hardware or software forwarding.

The original 3750 series have different SDM templates to maximize its limited resources for different usages, e.g. pure L2 vs. routing, etc.  Your particular model has somewhat greater hardware resources than the other 3750s of the same series and it offers an additional SDM template unique to that model.

See

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a00801e7bb9.shtml

Lastly, Jon also mentioned the performance specs for your individual switch, but if your running your pair as a stack, you may need to account for ring bandwidth vs. the internal switch bandwidth.  For this series, the stack ring bandwidth is also noted as 32 Gbps, but it's really dual 8 Gbps (duplex) ring ports.  For the traffic level you've mentioned, this should be just fine too.

[Jon Marshall]

Jon is 99.999% correct

Well, that is pretty accurate  

Didn't really want to go into when a packet is software switched at L3 as it would only create confusion and if configured properly it should be a very rare occurence but you make a valid point.

Jon

[Joseph W. Doherty]

Disclaimer

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.

Liability Disclaimer

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.

Posting

Jon is 99.999% correct

In our industry, we call that 5 nines. 

You're 100% correct about the risk of creating confusion with too much information, especially re: the original poster's question.  Often it's difficult deciding when an extra factoid should be mentioned.  In this case, keeping in mind others read these posts, didn't want such readers to infer L3 switching performance is always the same as L2 switching performance.

[perpaal]

Thank you for pointing that out.

By the way, can some of you reccomed witch of the latest IOS versions I should use for this pupose (main ISP router)?

And is there an overview of IOS and boot versions for these units anywhere?

[paolo bevilacqua]

For switches, IOS is not often buggy as for the routers, you might very well be going with whatever they come with.

[perpaal]

They have 12.2(58)SE

Seems to still be the latest, so should be ok...