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how to configure Voice VLAN on GS724TPS

Discussion in '3CX Phone System - General' started by hfournier, Sep 12, 2012.

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  1. hfournier

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    I have 2 stacked GS724TPS Smart Switches. Ports 2/g15 - 2/g23 are configured to VLAN2 (192.168.2.0/24), while all other ports are part of the Default VLAN1 (192.168.0.0/24). The firewall appliance has a LAN port setup for each LAN and serves DHCP to each in their appropriate subnet. Both subnets use the firewalls WAN port for Internet access. So basically, the two don't talk to each other.

    I want to use Voice VLAN to automatically handle the voice traffic. I've already setup OUI entries for the Grandstream phones and the Patton FXO gateway.

    When I go to enable VoiceVLAN, the VoiceVLAN ID dropdown does not allow me to select the Default VLAN1. I don't want the phones on VLAN2, so I created VLAN3. However, if I enable VoiceVLAN to VLAN3, how will the phones get their IPs? There's no DHCP server on VLAN3. Furthermore, the phone system is 3CX, which is installed on the server in the Default VLAN1 subnet (192.168.0.x). So VLAN3 has to be able to talk to the server for DHCP and 3CX, but I'm not sure how to configure that. Do I just move everything from VLAN1 to VLAN3 so that they're all in the same subnet?

    Sorry if this is basic... I'm fairly new to Smart Switches, so I need some guidance to get this right. Thanks.

    Henri
     
  2. lneblett

    lneblett Well-Known Member

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    Well, the first question that comes to mind is why the need to create a VLAN for what appears to be 9 phones?

    Some folks will argue the notion that separating voice from data is a "best practice". As you now see, there are some added complications that have to be considered. VLAN 1 is the default and is normally reserved and why the device will not allow a change. You could make the other device(s) (Router, DHCP server (and Scopes), 3CX NIC (assuming server has more than one) etc.) ports members of both VLANS or, not knowing more about the available recources and such, invoke complete isolation of the Voice by assigning fixed IPs and then having a dual port WAN router capable of supporting multiple static public IPs.
    Here is a link that may help you get a feel for how to handle:
    http://support.netgear.com/product/GS724TPS

    You will simply have to assess the network, devices and goals of what the VLAN will bring to the table in order to determine the best implementation, so hopefully the link will help.

    For 9 or 10 devices I am just not certain that I would immediately jump on the "best practice" theory. To me, for such a small population of devices, I think it complicates matters more so than it helps. You may have other reasons to want/need, even if simply educational, but what I normally see is that folks will buy a VLAN capable switch and then immediately think that VLAN'ing voice traffic will somehow or another improve performance or ease troubleshooting. This may be true in some large scale applications or even with Cisco and other proprietary systems (not SIP), but your description of the issue/scenario makes me think that perhaps a VLAN is not needed or necessary. Keep in mind that if all the phone devices (9) are in use at the same time , collectively they will likley use less than 2% of the available bandwdth of a 100Mbs network. Your switches are 1Gbs capable, but I have no idea of the built-in, pass through phone switch or other devices on the network capabilities.
     
  3. hfournier

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    Thanks for the response.

    VLAN2 (and the 9 devices that are part of it) is for a classroom of computers, and was setup that way to isolate them from the office LAN. So those are not the phones.

    There are actually 12 phones in the office. Currently, they are all part of the default LAN. There are also 2 remote extensions for a total of 14. However, from your message, it doesn't sound like there's much difference between 9 or 14 phones in terms of volume of traffic. FYI - They only have 4 PSTN lines and one SIP Trunk.

    Yes, the switches are gigabit and I wired the office with all new CAT6 during a full gut reno this past winter. The workstations are all newer Dell Vostro models with gigabit adapters and the server is a Dell T310 with dual gigabit. It's running SBS 2011 Essentials, so only 1 NIC is in use. The only things that aren't gigabit are the phones (Grandstream GXP-2110).

    The client says that they're getting dropped calls. They're looking at ditching the 3CX and Grandstream system for another solution. The alternative solution provider told them that they should implement QoS on a separate VLAN on the switches. So... here we are.

    I'm not convinced that they're actually getting dropped calls. The first time they reported it, it ended up being cell calls being dropped at the other end. The second time they reported it, I traced the calls in the logs and found that Extension A called Extension B, heard an incoming call, hung up and answered the incoming call. Meanwhile, Extension B answers and no one is there. Must be a dropped call... NOT. I've asked them to send me the times when other calls are being dropped, so I can check the logs, but haven't got anything else.

    I think I'm fighting a ghost or mirage and so far, I'm losing.
     
  4. lneblett

    lneblett Well-Known Member

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    Lovely.

    From your description, there is no technical reason to implement a Vlan for the voice. The vlan for the classroom I fully understand and endorse.

    The network can support 1gb, and the phones support 100Mbs, which also means that the computers attached and behind the phones are also limited to 100Mbs. You can still implement QOS in your current configuration. The bottom line is that the "pipe" can only support a given amount of data no matter how you segregate, divvy or otherwise try and manage. The more you try and manipulate the data, the more data you create with the additional info that must now be carried and acted upon. As I mentioned earlier, you can still set QOS now, but keep in mind that QOS is only applicable to the internal network and loses all meaning when data hits the Internet.....which I assume it does on an open connection to the external connections and to your Sip agent. It has no bearing once it he data reaches the PSTN gateway. While I may be sorely wrong, I just don't see the likelihood of your network being so saturated that it causes dropped calls. If the network is indeed saturated, a vlan won't help matters at all, but QOS might to some small degree. I simply do not see less than 2Mbs on a 1Gbs network being any concern and again that assumes all phones.on calls at the same time.

    Now then, it could be that your Internet connection may not be robust enough to support the sip agent, the external connections and their web needs, or.....your competition is using the issue to play upon the emotions of the client. I am guessing that perhaps they are offering a hosted solution and touting VPN or other dedicated circuit by which they claim to carry QOS across the network. They will also implement a vlan to isolate the data to their network operation center (NOC) but it will have nothing to do with or ease the internal data transmission requirements.

    You may have to attempt to placate the client by doing the vlan and all, but it could be for naught if the client is simply using the "issues" as an excuse. You might consider looking for a network monitor (there are likely free utilities on the internet to be had) that can record utilization over some defined period so you can truly assess just how saturated the network is and just maybe you can convince the client that its not what he is being told and if there really is an issue to provide better info so you can address.
     
  5. hfournier

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    Actually, I ran separate drops for data and voice, so the computers are not connected to the phones. They're connected directly to the CAT6 wall jacks, so they're taking full advantage of the gigabit LAN.

    The slowest thing on the network is the Patton gateway (SN4114). I just checked its interface and the Ethernet port is set to 10 MBps half duplex. I'm not sure if that's a default or recommended setting for 3CX. It's not something I changed since its installation. Now, I'm not sure if it should be left as is, changed to 100 full duplex or just set to auto. Could this be the problem?

    As for QoS, you mentioned that it only applies to the LAN. But since the "dropped calls" they're complaining about would be coming through the PSTN lines and Patton gateway, then the LAN is the only relevant part (no Internet). So having QoS should be beneficial in this particular scenario. But, as you also mentioned, the amount of traffic we're talking about is pretty low compared to the networks capacity, so how beneficial would it really be?

    I agree, I think it is being used as an excuse (i.e. red herring).
     
  6. hfournier

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  7. lneblett

    lneblett Well-Known Member

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    Glad you mentioned the issue on the 4114. I just installed one yesterday......and I thought I caught a gliimpse of a message indicating 10Mbs, but I wasn't sure. With your observation I will be certain to go back and check. Thanks.


    It is hard to say if any performance improvement will be noticed by either changing the 10Mbs to sometihing else of by using QOS. Nevertheless, I would do both if for no other reason that it certainly can't hurt and then you can at least explain to the client that they are indeed running QOS and further "try" to explain how a VLAN only brings a level of complication and overhead to a small network that really has nothing to gain. Use the school/training as the example of how a VLAN should be used......to isolate a segment of users.
     
  8. jpillow

    jpillow Well-Known Member

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    This switch has auto voice VLAN, you simply put in the first two octets of the MAC address and the switch should automatically put those ports in a voice VLAN.
     
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  9. hfournier

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    @jpillow

    Yes, it does, and I've already added the Grandstream MAC octets to the OUI. But, as I mentioned in my original post, when you enable that feature, there's a dropdown box to select which VLAN to use. If I create a new VLAN3 for just the phones, I have no DHCP server on VLAN3 and 3CX is installed on the server, which is part of the Default VLAN, which can't be selected. So this is where I'm stuck.
     
  10. netswork

    netswork Active Member

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    I would recommend always hard setting speed and duplex on any gear like the patton gateways. Auto negotiation does not always work as you want it to. If the switch is manageable I would hard code it on the switch as well.
     
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