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Wired Networks Thread, Cisco / Vendor Docs to explain... in Technical; Why VOIP / IP Phones should be on a different VLAN to other devices on a network. Does anybody know ...
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    cpjitservices's Avatar
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    Cisco / Vendor Docs to explain...

    Why VOIP / IP Phones should be on a different VLAN to other devices on a network.

    Does anybody know where the Docs are explaining why either by Cisco or another network vendor ?

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    Don't know where the docs are but it will be because of broadcast traffic. A VLAN's broadcast traffic is limited to it's own VLAN so it will cut down on the traffic reaching your desktops and slowing things up

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    Check the Cisco guy's information on this page:

    https://supportforums.cisco.com/thread/277836

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    The idea is that you keep time sensitive traffic in it own sub network. You can then also apply per vlan QoS.

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    cpjitservices (24th May 2012)

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    Thanks everyone ... what I need is a pdf or something similar from Cisco / Avaya / HP etc etc that would give facts about why VOIP needs to be on a separate vlan, It's to prove to an external company that some work they have done is not right - for example they've installed a phone system in a business and they have told the company that VLANS are not supported by said Phone System which to me smacks as useless!! So the Phones, PC's and Servers what they have are now all on the same Network.

    If anyone knows of any such documents that would outline the facts... I found one just now from Cisco but need others like HP or the likes.

    Thanks everyone!

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    cpjitservices (24th May 2012)

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    Cisco's SRND docs for Unified Communications can be found here: Cisco Unified Communications System

    The principles here apply to any voice design:

    When you deploy voice, Cisco recommends that you enable two VLANs at the access layer: a native VLAN for data traffic and a voice VLAN under Cisco IOS or Auxiliary VLAN under CatOS for voice traffic.

    Separate voice and data VLANs are recommended for the following reasons:

    •Address space conservation and voice device protection from external networks

    Private addressing of phones on the voice or auxiliary VLAN ensures address conservation and ensures that phones are not accessible directly through public networks. PCs and servers are typically addressed with publicly routed subnet addresses; however, voice endpoints may be addressed using RFC 1918 private subnet addresses.

    •QoS trust boundary extension to voice devices

    QoS trust boundaries can be extended to voice devices without extending these trust boundaries and, in turn, QoS features to PCs and other data devices.

    •Protection from malicious network attacks

    VLAN access control, 802.1Q, and 802.1p tagging can provide protection for voice devices from malicious internal and external network attacks such as worms, denial of service (DoS) attacks, and attempts by data devices to gain access to priority queues through packet tagging.

    •Ease of management and configuration

    Separate VLANs for voice and data devices at the access layer provide ease of management and simplified QoS configuration.

    To provide high-quality voice and to take advantage of the full voice feature set, access layer switches should provide support for:

    •802.1Q trunking and 802.1p for proper treatment of Layer 2 CoS packet marking on ports with phones connected

    •Multiple egress queues to provide priority queuing of RTP voice packet streams

    •The ability to classify or reclassify traffic and establish a network trust boundary

    •Inline power capability (Although inline power capability is not mandatory, it is highly recommended for the access layer switches.)

    •Layer 3 awareness and the ability to implement QoS access control lists (These features are recommended if you are using certain Unified Communications endpoints such as a PC running a softphone application that cannot benefit from an extended trust boundary.)

  10. Thanks to Destinova from:

    cpjitservices (25th May 2012)

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    Found it! Should do the trick nicely!

    Cheers!

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    Quote Originally Posted by cpjitservices View Post
    Thanks everyone ... what I need is a pdf or something similar from Cisco / Avaya / HP etc etc that would give facts about why VOIP needs to be on a separate vlan, It's to prove to an external company that some work they have done is not right - for example they've installed a phone system in a business and they have told the company that VLANS are not supported by said Phone System which to me smacks as useless!! So the Phones, PC's and Servers what they have are now all on the same Network.

    If anyone knows of any such documents that would outline the facts... I found one just now from Cisco but need others like HP or the likes.

    Thanks everyone!
    The phone system does not support VLANs, or the business's equipment?

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    @Mehmet - what cpjitservices means is that the Phone vendor told him that the Phone System doesn't have any VLAN capability.

    I get this all the time - CCTV, BMS, Cashless Catering - they all tell me their kit doesn't support VLANs or even work on VLANs sometimes. Usually it's because they've either misunderstood what we're saying, or they don't know what a VLAN is, or because they don't want to deal with any support issues over a routed network should they arise.



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