VOIP no VLAN - issues with conversation dropping out

[fiza]

Is everything on one switch? Can you see any usage graphs for that switch?

 

The 3 phones are on one switch but the settings are the same on all switches.

 

A shot in the dark but we have Intrusion Prevention turned on, on our Sophos firewall and we had to create exceptions so that it didn't interfere with our IP Office system

 

The FW is provided by our ISP and they say they have checked their end and nothing is wrong. No settings have been changed on the firewall but they have also said that this VLAN bypasses content filtering and FW rules so nothing should interfere with the phones.

[fiza]

I have just read this thread on Spiceworks where they argue that if both phone and PC are on the same wire then VLANs don't do anything.

 

You won't be isolating broadcasts because they are all coming down the same wire to reach the data vlan anyways.

 

Could this be true?

[mavhc]

If there's a PC plugged in, yes, but that's easy to test, unplug it. Broadcast traffic is overblown as an issue, unless something's going wrong or it's on wifi

[fiza]

I've got a brick wall now on what I can do with the knowledge I have. Does anyone know of a company in the London area that can come in and diagnose/fix the issue we have? The switches are Cisco small business.

[AlanD]

Sorry not read the whole thread....

 

Are these drop outs between internal calls - or are they only for calls which are external? I can see you have been advised to use a VLAN for your phones. I would agree with that as a starting point. And then make sure QoS is enabled at every switch for that VLAN. And make sure you don't have any loops (or possibly a loop created using wireless). If you have any wireless...I'd be tempted to turn that off for a day to see if that is related to the problem. My guess is it will be because of things like tablets and printers using "Bonjour" to discover themselves in the background - which can produce an enormous clutter of traffic....but once you have created the voice VLAN that will disappear.

 

Getting someone in isn't going to have any magic answers or tools....you can do what they are going to do. Turn bits off (starting with wireless) until you have narrowed down the issue. Yes it will be disruptive. They will do this too.

 

Its possible that even "internal" calls are actually going via your external internet - do you host your own VoIP exchange internally? So my second guess is its your internet router/filter/connection that some issues....or even an issue with whoever is hosting your VoIP.

[fiza]

Sorry not read the whole thread....

 

Are these drop outs between internal calls - or are they only for calls which are external? I can see you have been advised to use a VLAN for your phones. I would agree with that as a starting point. And then make sure QoS is enabled at every switch for that VLAN. And make sure you don't have any loops (or possibly a loop created using wireless). If you have any wireless...I'd be tempted to turn that off for a day to see if that is related to the problem. My guess is it will be because of things like tablets and printers using "Bonjour" to discover themselves in the background - which can produce an enormous clutter of traffic....but once you have created the voice VLAN that will disappear.

 

Getting someone in isn't going to have any magic answers or tools....you can do what they are going to do. Turn bits off (starting with wireless) until you have narrowed down the issue. Yes it will be disruptive. They will do this too.

 

Its possible that even "internal" calls are actually going via your external internet - do you host your own VoIP exchange internally? So my second guess is its your internet router/filter/connection that some issues....or even an issue with whoever is hosting your VoIP.

I hadn't thought of switching the wireless off for a day so thank you for the suggestion, I will try that. The phone system is hosted and was sold to us via our ISP. The ISP say they have checked everything their end and all is good. The phones have worked fine for a year so it could well be the additional wireless devices that have been added since. The switches are Cisco small business and have something called smart port which recognises phones and then puts them on the voice vlan. The voice vlan is preconfigured for QoS. I have put 3 of the phones on this vlan but the problems persist with both internal and external calls.

[AlanD]

OK, so its hosted. What happens to voice calls when they reach your core switch? Do they get passed separately to your router....does your router maintain that QoS? Are you using a leased line (or FTTC or cable modem?) Do you reserve bandwidth for voice traffic - or rely on QoS? Think I might be asking the ISP for names of other schools businesses that use their Voice service - to contact them just to double and triple check this is not something at their end. Wouldn't take their word for it.

 

...might be worth updating any firmware in Cisco...routers...printer firmware....printer drivers....

 

(Why only 3 phones on this VLAN rather than all of them? Is that because it was working before...with without that...and so just a test?)

 

Is your wireless on the same native VLAN as phones? Or as the computers?

 

Sorry - I'm not sure answers will solve the problem - but just trying to get a picture of what you have - and your reasons for doing it that way.

 

I hear the statement....it used to work.....so its tempting to think its something you have added/changed or updated....but it could be something further upstream with your ISP despite their denials....hence needing to find other customers that use their Voice service.

[Blue_Cookeh]

I have just read this thread on Spiceworks where they argue that if both phone and PC are on the same wire then VLANs don't do anything.

 

 

 

Could this be true?

 

That's not really how it works - the switches will prioritise VoIP traffic because it's time sensitive (so long as the VLAN is tagged as voice, on HP and Juniper switches anyway - I suspect the same is true with Cisco).

[AlanD]

That's not really how it works - the switches will prioritise VoIP traffic because it's time sensitive (so long as the VLAN is tagged as voice, on HP and Juniper switches anyway - I suspect the same is true with Cisco).

 

That would be an over simplification. I agree you only have a set bandwidth...nominally 1Gb/s and dividing that up into vlans doesn't help deliver any more bandwidth to voip...although you might be able to throttle bandwidth on the domain LAN with some switches....The main improvement is to remove all the noisy clutter that bonjour and other broadcast services are creating which voip devices would hear and decode even if they then decided the traffic was not for them.

[Oaktech]

Why can't it happen in the short term? How long is it going to take? Configure a scope, configure your switches. 40 phones and 70 computers you should have that done inside an hour.

 

That rather depends on the wired network not being a massive cluster:censored: and you actually knowing what ports go where. My experience in schools is that this is rarely the case. I have Vlans set up at my main school, but my second school we have no idea where half the ports go. Our summer holiday project is to accurately map the ports and remove unused patches.

 

I would always advocate VLAN with QoS for voice.

[mjk]

That rather depends on the wired network not being a massive cluster:censored: and you actually knowing what ports go where. My experience in schools is that this is rarely the case. I have Vlans set up at my main school, but my second school we have no idea where half the ports go. Our summer holiday project is to accurately map the ports and remove unused patches.

 

I agree. it's really unfortunate that people don't look after their infrastructure. I think it's the number one infrastructure that network managers are paid to look after as it underpins all the technology in the college. Good for you making it a top priority./

[AlanD]

I agree. it's really unfortunate that people don't look after their infrastructure. I think it's the number one infrastructure that network managers are paid to look after/

 

...I've always though backups were the Number One priority....To do them, check they are done, and test they work. Refuse to do anything else until that can be ticked off as job done weekly/daily.

[DJ-1701]

...I've always though backups were the Number One priority....To do them, check they are done, and test they work. Refuse to do anything else until that can be ticked off as job done weekly/daily.

 

Well, with a multi server setup the Infrastructure needs to be working before you are able to backup does it not?

[mjk]

...I've always though backups were the Number One priority....To do them, check they are done, and test they work. Refuse to do anything else until that can be ticked off as job done weekly/daily.

Not according to our DR strategy. The network must be up and running first!

[Oaktech]

Not according to our DR strategy. The network must be up and running first!

 

Quite. No point having a bunch of servers running beautifully if no-one can connect to them or the connection is unreliable.

[psydii]

That actually leads one to a rediscovery of a reasonable school network design principle:

 

Each service ought to work if completely isolated onto their own vlan/switch.

 

e.g. Servers/Backup, Phones, CCTV, Cashless Catering, AppleTV etc.

 

You then configure each service boundary to be resilient to loops, and and the connect them together through a router with ACLs to provide some security and isolation of traffic that does not need to cross the boundary, then optimise for the type of traffic e.g. VIOP and QoS.

[AlanD]

Don't need a network to do a windows backup - to a USB3 SATA drive. So I would be doing a basic backup even if core network went down....but its up to you.