From: Tarun Pahuja (pahujat@gmail.com)
Date: Fri Oct 26 2007 - 13:56:57 ART
Gregory,
Scott did a tremendously job in explaining the concept.
On Many switches even thought the port is configured as a trunk, the
phone would still come up and register with the Call Manager.
One of my customers called me one day and told me that his 6500 switch
had 72% process utilization which was impacting performance.On
Investigating the matter I found out that he had mis configured all 48
ports on a line card as trunks ports for IP Phone connectivity.
Removing the trunking on those ports and making them part of voice and
access vlan brought the CPU utilization back to 19%.
Some old network module switches still require administrator to
configure them as trunk ports with native vlan for IP Phone
connectivity.
HTH,
Tarun
On 10/26/07, Scott Morris <smorris@ipexpert.com> wrote:
> IP Telephony itself isn't part of the lab, but familiarity with some of the
> topics is a "good thing to know". :)
>
> In a nutshell, your voice vlan is sent with an 802.1Q tag and your PC/Data
> traffic is sent untagged. In a "pure trunk" concept this means your PC data
> would be your native vlan and you'd have a trunk running.
>
> For security purposes, people used to get all up in arms about needing to
> use "switchport trunk allowed" and restrict what things could or could not
> be sent over that trunk for the great fear of hackers. Cisco has made it
> simpler with most switches where you can now simply be in 'switchport mode
> access'.
>
> This, when we look at it, doesn't allow trunking. The 'switchport voice
> vlan' command, however, provides a specific override allowing tagging of one
> single vlan only. So we've made things better for the security conscious as
> well as simpler for the configuration.
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
> #153, JNCIS-ER, CISSP, et al.
> CCSI/JNCI-M/JNCI-ER
> VP - Technical Training - IPexpert, Inc.
> IPexpert Sr. Technical Instructor
>
> A Cisco Learning Partner - We Accept Learning Credits!
>
> smorris@ipexpert.com
>
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
> http://www.ipexpert.com
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Gregory Gombas
> Sent: Friday, October 26, 2007 11:27 AM
> To: Cisco certification
> Subject: IP Telephony Topics for R+S
>
> Not sure if IP telephony is in scope for the R+S but seems to crop up in the
> IE workbooks a lot. I was hoping someone could help clear up some confusion:
>
> 1. When connecting an cisco IP phone to a 3550/3560, does it automatically
> create an 802.1q trunk?
>
> 2. According to the DOC cd:
> "You can configure an access port with an attached Cisco IP Phone to use one
> VLAN for voice traffic and another VLAN for data traffic from a device
> attached to the phone. "
>
> How is it possible two have two different VLANS run over a switch port
> configured in access mode?
>
> 3. Can someone recommend some good (but short) reads for connecting IP
> telephones to Cisco switches? I already have this one:
>
> http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12240se/scg/swvo
> ip.htm
>
> Thanks,
> Greg
>
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