SPA5xx and VLAN configuration

[christos85]

Hello,

Do you know which methods the IP Phones use to get configured in order to work on a particular Vlan? (For example via CDP protocol)

And also if the phone receives VLAN settings from multiple methods, then which is the priority that the phone follows?

Thank you in advanced for your help

[Tom Watts]

Hi Christos, CDP or LLDP-MED. I personally don't know if there is a "priority" but I would also say it is fair enough you shouldn't be running LLDP-MED network policy inconjunction with a CDP voice policy.

If you have phones that don't support CDP you should be using LLDP-MED if the 3rd party vendor phones support it.

-Tom
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[christos85]

Hi Tom, thanks for your quick answer. As far as I know you can also set manually a static VLAN to the phone (correct me if I am wrong).

For example in case that I set manually the phone to use VLAN 50, but at the same time there is a configuration on the network device (switch) which determines the VLAN 60 as the Voice VLAN and with CDP or LLDP-MED enabled. Then which of the two VLANS will the phone use?

I believe that there should be some “priority”.

[Tom Watts]

If you static assign the VLAN, neither cdp or lldp will tell the phone where to go since that field is occupied statically. You could also use DHCP options to have the phone be fed vlan information if you'd take it that far (back in time )

-Tom
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[christos85]

Thank you very much Tom. It just started becoming interesting with your last answer . I will look into that as well, as I want to examine every single parameter and see the phones’ behaviour.

[edvandijke1980]

Hi Tom,

do you maybe have some additional information on how to puch the vlan through DHCP. I've also got the problem that cdp or lldp isn't available.

I've tried serveral option in my DHCP server (like option 132), but so far without result.

And with all i've read so far I get the idea that the SPA5xx phones aren't able to get their vlan through dhcp.

[Dan Lukes]

It's to late to got VLAN number in DHCP response. DHCP DISCOVER/DHCP REQUEST packets needs to be sent in appropriate VLAN, so you need to know the VLAN before DHCP is started.

I assume there is no such DHCP option nor will be in the future.

[edvandijke1980]

Hi Dan,

last night I've got the idea that there is no other option for the SPA5xx phones, because if i'm not misstaken the SPA's only suppport DHCP options 66,150,159,160.

I've got the idea of this all because i've seen some cases where the customer did this on their old system.

And so I started my little search

I've have found indeed that some phones can be put in a vlan through option 43 for example.