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When should I create VLANs?

Scott Waterhouse_1
Occasional Contributor

When should I create VLANs?

I run a mid-sized shop with about 70 users. We have about 70PC's, a dozen servers, 70 IP phones, and about 25 other devices (printers, time clocks, etc.) on the network for a total of about 190 devices. Most of the device to switch communication is 10/100MB and switch to switch backbones are 1000MB (either copper or fiber depending on distance).

My current setup:
We have a 2824 as the core switch (including servers) with the edge switches comprising of two 2650's, two 2626's and a 4000M. There are also some crap netgear hubs/switches in some funky places that are being phased out as quicly as possible. (This is a large manufacturing facility that has offices in fairly remote locations that needs signifigantly more fiber than it has but no money for fiber!)

Overall bandwith utilization is low with backbone speeds rarely exceeding 50MB/s during normal daily load and usually averaging about 15 MB/s.

My question is should I setup VLANs or not? Everyone always says to put the VOIP tarffic in its own VLAN but with my low utilization I am not sure it's warranted. I am running into some minor problems with echo on the phones (they are new we just implemeted VOIP about a month ago) but that could be from so many sources I am trying to eliminate the network as one of them.

Thanks for any help!

Matt Hobbs
Honored Contributor

Re: When should I create VLANs?

Hi Scott,

With these IP Phones, do you have PC's connected into them? i.e, sharing the same port back to the switch? If yes, then I would more seriously consider implementing VLANs. Otherwise you're likely to run into the problem of voice quality issues when the PC behind it starts download/uploading a large file, email, etc.

If the IP phones have their own switch port then this isn't so much of an issue unless there's a lot of broadcast/multicast traffic on the network.

There are also other considerations, for security/privacy issues it may be a good idea to put your voice traffic on a seperate VLAN just in case a bad guy wants to start capturing traffic on your network and listening in on others phone calls.

If you do decide to setup VLANs then it's pretty straight forward for your type of setup, you may not even need to enable 'ip routing' if there is no real reason for voice traffic to cross over into your data VLAN.

By the way, what sort of time clocks do you have? (I'm looking for one)

Scott Waterhouse_1
Occasional Contributor

Re: When should I create VLANs?

The PC's are hanging off the IP Phones and I I can see your point about the large data transfer effecting voice quality even for very short periods of time.

I guess I will set it up since I don't have a lot to loose.

As for the the time clocks we got them as part of our Time and Attendance system and there are no manufacturer markings on them whatsoever. The time system we use is ADTTime (www.aditime.com) and have been very happy with it so far.