Document bridge support for flooding ieee-reserved (e.g., LLDP)

[jovatn]

We lack an example showing how to make a bridge flood LLDP rather as opposed to snoop them.

One could add such an example to the Bridge section, possibly as a subsection on same level as MAC Bridge and VLAN Bridge?

Ideas below. Probably good to add a lego picture as well with a bridge and four Ethernet ports, illustrating that LLDP packet will be flooded.

admin@example:/config/> edit interface br0
admin@example:/config/interface/br0/> set bridge ieee-group-forward <TAB>
  [0..15]  List of IEEE link-local protocols to forward, e.g., STP, LLDP
  dot1x    802.1X Port-Based Network Access Control.
  lacp     802.3 Slow Protocols, e.g., LACP.
  lldp     802.1AB Link Layer Discovery Protocol (LLDP).
  stp      Spanning Tree (STP/RSPT/MSTP).
admin@example:/config/interface/br0/> set bridge ieee-group-forward lldp
admin@example:/config/interface/br0/>