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New Member

Complicated SIP conf causing audio issues

I'm having issues with my VoIP quality that I'm not able to track down.

Network configuration: 

WAN (cable) -> RV320 (single WAN) -> SG300-10 -> SG200-8 -> SPA112.

VLAN2 = Network, VLAN3 = IPTV (isolated to SG300), VLAN4 = Voice


I've got nothing but Cisco SMB equipment all the way through. I removed a couple of Tomato based routers for the RV320 and SG200-8. Ever since I've have intermittent audio quality on the caller's side only. It happened with my FreePBX machine installed as well so I've removed it from the equation for simplicity. I think we can eliminate the WAN as a possible issue as well, since nothing has changed there.

The voice setup and configuration for this many interlinked devices has turned out to be too much for my skill level, but I really need the Dual WAN in the future and the SG200 on the edge of my network to support a handful of devices.


At what points along my network should I be configuring Voice and where should I just pass the packets along? What is the best method to get voice on to VLAN4 and prioritized to avoid this packet/jitter issue?



Everyone's tags (1)
New Member

I should add that all my

I should add that all my firmware is up-to-date and all devices were reset before configuration.

VIP Gold

The caller affected by the

The caller affected by the issue is a phone connected to SPA112 or someone outside of your's network ? And where is the called phone ?

New Member

The caller is outside the

The caller is outside the network. I've tried different callers, same result. The called phone is attached directly to line1 on the SPA112.

These are callers that had no issues before installing the RV320 and SG200.

VIP Gold

OK. Although dedicated to

OK. Although dedicated to slightly different environment, the following article should help you:

Basic QoS Setup on a Cisco SG 200 Switch


New Member

The second paragraph on that

The second paragraph on that article mentions it doesn't involve a VLAN aware router or layer 3 switch. Both of which I do have.

It does mention LLDP to control QoS for VoIP. I did try setting this up, but it doesn't seem to have helped. I'm still not sure where to do this, at the SG200 or SG300? Both?

VIP Gold

Unfortunately we don't know

Unfortunately we don't know what/where data are overloading your's infrastructure.


Generally QoS needs to be configured on both.


But you should consider "divide et impera" principle. Disconnect SG200-8, connect SPA112 directly to SG300-10. Configure QoS on SG300, verify it works correctly (e.g. the VoIP is working well even if you will try to overload SG300 and WAN from other device connected to SG300).

Connect SG200 back, reconnect SPA112 to it, configure QoS on SG200.


New Member

Good call. It was on my list

Good call. It was on my list of things to try, but I was hoping this would be a quick fix somewhere. No such luck

It  seems to be 100% on the RV320/SG300. LLDP identifies it in the neighbourhood, and shows it under the network policy table as Voice tagged on VLAN4. Sound quality is perfect so far. Looks like that is all configured correctly.

On the RV320 there is no reference anywhere to it. LLDP only sees the SG300. Is that normal? The router doesn't seem to have a place to check that. Should I just assume the router is passing it on through the WAN correctly? LLDP on the SG300 does identify the RV320 as a router on the correct port.

New Member

Strange... I have the voip

Strange... I have the voip port setup on the SG200 as 2U/4T, but the SPA112 wants to take an IP address in VLAN4. That seems weird to me as the SPA112 isn't specifically being told to connect to a VLAN in it's network settings. Is the LLDP taking control of the VLAN assignment? I thought it was only there to redirect VoIP packets.

Does this mean once I set this up all communication with the SPA112 will be over VLAN4? That's ok, it just wasn't how I pictured this working in my head. Seems it's just easier to put the SPA112 on VLAN4 and be done with it.

VIP Gold

I'm unsure I understand.Is

I'm unsure I understand.

Is the sound quality perfect if the SPA112 is connected directly to SG300 ? Even if there's attempt to overload the WAN by other traffic ? Then SG300 configuration seems to be correct.

Note I'm expert on SPA112 and I'm familiar with switching principles, including priorities. I'm no expert on SG[23]00 configuration. So some other expert need to answer what's normal on SG300.

Is the LLDP taking control of the VLAN assignment?



New Member

yes, sound quality is perfect

yes, sound quality is perfect attached to the SG300. It seems to be the SG200 causing the problems.

VIP Gold

Thus you know the further

Thus you know the further steps.SG200 needs to be configured correctly. In advance you should identify the source of SG200's congestion.

New Member

I basically gave up on the

I basically gave up on the VoIP for a bit and swapped over to setting up some of my VPN equipment. Imagine by surprise when I started seeing some of the same intermittent communication issues I was seeing with the VoIP.

This got me thinking... what else could be causing this. Assuming the rest of my hardware is fine and VLAN is setup correctly.

Then I found this:

STP. I'll do some more testing, but so far swapping the BPDU setting on the SG200 to filter seems to be working. I don't have any equipment passed the SG200 that need STP, so it should be ok.

What a crazy switch. Next time I won't cheap out and get the SG300.

VIP Gold

Someone may consider all

Someone may consider all those SMB switches to be cheap entry level ;-)

Glad to hear you solved the issue.

Consider rating of valuable responses, although I'm not sure there's been such one for you ;-)

New Member

SMB switches are a necessary

SMB switches are a necessary evil for home power users like myself. The enterprise stuff is prohibitively expensive and brutally overkill.

My SG300-10 has been absolutely bulletproof and I cry thinking about the daisy chained D-Link non-managed switches I was using before. Jury is still out on my RV320.

New Member

Ugh, well problems came back.

Ugh, well problems came back. I'm out of ideas. STP turned right off on the whole network didn't help. Unfortunately I don't have the time to commit to making this thing work. Sorry Cisco, it's going back.

VIP Gold

Despite you claimed you have

Despite you claimed you have no time to solve, I will give an advice.

Poor audio quality is mostly caused by packet loss, so high delay or so high jitter.

Hypothesis: All those condition are tied to overloaded network.

Verification: make sure the phone only end device connected - e.g. disconnect all computers, TV sets and so on. If it will help then you need to identify the device that's overloading your network (or WAN connection).

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