Implementing VoIP with SG300-28P

[Olabisi Igbayiloye]

Hi,

Please I need help.

I want to implement VoIP on my client network, currently the data network is using SG300-28P small business switches for user access.

According to my design the IP Phones (Cisco 9971 and 7942G IP Phones) are to connect to the small business access switches while the user PCs connects to the IP Phones.

My concern is I really don't understand how the small busness switches will advertise the voice VLAN to the IP Phones. I understand that the switches are suppouse to use LLDP/CDP for this but it seems the model I have can only do LLDP. The IP Phones and the PCs connected to them will be recieving IP addresses from an uplink L3 managed switch.

Has anyone done this before?

Can I have an explanation on how LLDP works (particularly regarding this scenario)?

Does it matter if the small business switch is in L2 or L3 mode for the VoIP implementation?

Thanks.

[Tom Watts]

Hi Olabisi,

The switch in l2 or l3 does not matter for voice implementation. It simply depends on what other hardware is on your network.

Since you have a l3 switch already, the SX300 should remain l2.

Here is a documentation I wrote for LLDP-MED deployment.

https://supportforums.cisco.com/docs/DOC-27005

-Tom
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[Olabisi Igbayiloye]

Thanks Thomas.

The doc made me understand some more things, I will revert if I have any more problems

[Olabisi Igbayiloye]

Hello Thomas, am still on this issue.

I realised that the firmware version on the SG300 switch (1.0.0.27) is lower to the one in your documentation, so the configuration does not follow the same as yours. The problem am having now is that the IP phone (7931) is not able to get the right IP address via dhcp, it attempts to pick IP address from the data network dhcp scope.

I cannot enable auto vlan membership unless I change the Interface VLAN mode to General, the phone does not get the right IP address even with this setting

The phone seems not to support LLDP (though cisco.com says it does)

I cant get the switch interface to be be members of both data and voice vlan

So am thinking, should I upgrade the firmware on the switch, maybe it will solve the problem

Does the default vlan affect voice implementation if the voice vlan is different from the default vlan?

Thanks.

[Tom Watts]

The 1.0.0.27 firmware is the original product release firmware. That software has a very limited feature set. The 1.0.0.27 does not have auto voice vlan, cdp or anything else that is particularly useful for voice applications.In addition, the switch has a fully supported CLI on later firmware versions.

The first thing you should do is upgrade to the latest firmware then factory reset the switch. The 1.2.7.76 code was a major firmware release that modified a lot of the inner-workings of the switch. A backup config file may or may not work correctly since the switch XML had a major overhaul.

-Tom
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