Ask the Expert: Voice VLAN implementation on Small Business switches discussion

[ciscomoderator]

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about Voice VLAN on Small Business switches with Cisco subject matter expert Aleksandra Dargiel.

In particular, Aleksandra will cover topics such as Smartports Macro, OUI based Voice VLAN, design and implementation with other Cisco infrastructure devices

Aleksandra Dargiel, CCNP S&R is a Subject Matter Expert in Cisco Small Business. She spend 4 years in STAC supporting Small and Medium Business customers and partners.  6 years hands on experience and lateral thinking allows her to drive resolution of complex technical problems.

Remember to use the rating system to let Aleksandra know if he has given you an adequate response. 

This event lasts through October 8th, 2014. Visit this forum often to view responses to your questions and the questions of other Cisco Support Community members.

[Sarah Staker]

Hi there.. 

I have a question..  

Is it better to use Telephony OUI or auto Voice VLAN on SG200?

[Aleksandra Dargiel]

Hi Sarah,

Thank you for starting the discussion :-)

If you have Cisco phones supporting CDP than the most seamless solution would be Auto Voice VLAN.

However if you are using 3rd party phones which do not support CDP you have to:

1. either add phone MAC address to OUI table so switch would treat its traffic as the Voice VLAN traffic

2. or simply configure phone to start tagging traffic with Voice VLAN ID

Please note: With the OUI Voice VLAN solution there will not be tagged traffic between the phone and the switch while with Auto Voice VLAN phone is told by switch to start tagging its traffic.

Regards,

Aleksandra

[Brandon Svec]

I would add that many phones support LLDP also and can use auto voice VLAN like a Cisco CDP phone.  I have even seen some non Cisco phones that have CDP (NEC DT700).

Interesting point about OUI Voice VLAN.  So really the phone sits on the native VLAN with no tagging, but the switch passes traffic from its MAC address to voice VLAN, I guess?

[Aleksandra Dargiel]

Hi Brandon,

Yes, ..."When the device is in Telephony OUI mode and a port is manually 
configured as a candidate to join the voice VLAN, the device dynamically 
adds the port to the voice VLAN if it receives a packet with a source MAC 
address matching to one of the configured telephony OUIs. An OUI is the 
first three bytes of an Ethernet MAC address. "... admin guide page 212

http://www.cisco.com/c/dam/en/us/td/docs/switches/lan/csbms/sf30x_sg30x/administration_guide/78-19308-01.pdf

Regards,

Aleksandra

[elite2010]

Hi Aleksandra 

I have noticed several times , the phone is working even without  tagging traffic Voice VLAN ID' ,

i saw this on 3560x switches , why  does it  works ?

eg : sw mo access

sw access vlan  10 ( vlan 10 is not voice vlan ) , and see there is no voice vlan tag 

Thanks 

[Aleksandra Dargiel]

Hi,

Actually Voice VLAN is active only on the access ports. It is dynamic VLAN and trunk is only operational when phone is present on the interface.

So to answer to your question voice vlan is most configured globally and enable on the interface. Port is regular access port when workstation is connected however when phone is plugged in and detected by switch. Switch would instruct (via CDP) to start tagging phone traffic and operation status of this port would be actually trunk.

you might verify this by checking show mac address-table. This is very useful command when trying to identify operational status of the ports.

I hope it sheds light on the subject.

Aleksandra

[elite2010]

HI,

The port is an access port . And Normally when i configure the access port  as below

interface GigabitEthernet3/3
 switchport access vlan 10
 switchport mode access
 switchport voice vlan 8

And once  i forget to  add ' switchport voice vlan 8' and the phone (6941)connected

it started to work !!

Thanks  

[Aleksandra Dargiel]

Hi,

This is not something I have seen before but was the phone actually in the default settings? and how exactly did you check this?

Aleksandra

[marlonvalerio]

Hi Aleksandra, good morning!

I'm having a problem with Lucent IP Phones in my network. They randomly reboots even in a middle of a conversation.

The phone provider claims that is a switch configuration issue.

It's a SG300 24P 

Thanks

Marlon

[Aleksandra Dargiel]

Hi Marlon,

It would be good to get syslog from the phone to understand the reason. You can also check if the same issue would be present if the phone is on the port configured as access. Do you have any enterprise devices on the network such an ASA.

Regards,

Aleksandra

[Aleksandra Dargiel]

Hi Marlon,

there are many various reason the IP phone would reboot starting from physical layer up the OSI model. If you suspect any problem with switch you can open ticket with Cisco Small Business Support team:

http://www.cisco.com/c/en/us/support/web/tsd-cisco-small-business-support-center-contacts.html

Regards,

Aleksandra

[Danny Yehya]

Hi,

We have a Cisco RV220W Router/Switch and a Matrix phone system.

All of the internal phones are on the LAN while we also have external phones connect to a One-to-One NAT for the VOIP System which is connected to a T1. The external bandwidth that is being used is only by the external phones connecting through the internet routing through the VOIP system (Eternity Matrix) and then going through the T1.

We also want to prioritize LAN traffic for for SIP based phones so if there is internal congestion the phones are prioritized. Since it is a Gigabit switch this is less of an issue.

We got a Netgear Smart Switch which isn't configured at the moment other than provide PoE for the phones. The model is GS752TPS. I know this could be configured some on that Switch but would rather keep it a "dumb" switch and let the Small Business Router handle as much as possible for VLAN assignments and/or QoS.

Thanks,

Danny

[Aleksandra Dargiel]

Hi Danny,

If the router is a "bottle neck" then it makes sense. However RV220 would only handle how the queues are emptied and not remarking. Is this the question?

Regards,

Aleksandra 

[Aleksandra Dargiel]

Danny,

It would be good idea to open this post in the Small Business Router section.

Regards,

Aleksandra