[asterisk-users] Understanding how LLDP works with DHCP

[Olivier]

Hello,

For years, I used to configure SIP phone VLAN membership through a DHCP
server.

Here are the details:
- I dedicate a LAN port on a switch to voice VLAN
- somewhere else, I configure a DHCP server to serve LAN addresses within
voice VLAN
- any other switch port connected to an other DHCP server is explicitely
excluded from voice VLAN
- new SIP hardphones are first connected to the dedicated voice VLAN port:
after several reboots, they get an address within voice VLAN address range
and save VLAN tag somewhere within their persistent memory
- SIP phones are then moved to an other switch port: as they boots, they
request a LAN address using previously received VLAN tag.

Now I would like to improve this process using LLDP.
I ran a couple of tests in my lab and still have some questions:


1. My lab switch sends within LLDP frames, a list of VLANs. One is named
"default" and the other is named "voice".
Do LLDP-capable phones look for a specific name to elect the VLAN tag they
will later use to build DHCPDISCOVER request or do they look for something
else (medPolicy) ?

2. With LLDP, do you still need your DHCP server to embed VLAN membership
data within DHCPOFFER or is it a thing of the past ?

3. Have you been successfull with LLDP on a KVM guest networked to an
LLDP-enabled switch through a linux bridge (see [1]) ?
Where can I find information regarding the line bellow:
echo 16384 > /sys/class/net/<bridge_name>/bridge/group_fwd_mask


[1]
https://thenetworkway.wordpress.com/2016/01/04/lldp-traffic-and-linux-bridges/


Best regards
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