Just a quick question what type of conneciton is this? A braidge??
encapsulation dot1Q 1012
ip accounting output-packets
no snmp trap link-status
no cdp enable
xconnect 172.19.103.3 500 encapsulation l2tpv3 manual pw-class ether-pw
l2tp id 500 600
l2tp cookie local 4 12345
l2tp cookie remote 4 54321
l2tp hello l2tp-defaults
It is a layer 2 VPN tunnel or at least one end of a VPN tunnel. In effect it is extending a L2 vlan across a L3 routed IP network ie. you can have the same L2 broadcast domain in 2 different locations separated by a L3 network.
So if a client in site 1 sends out a broadcast to it's local subnet machines on the same subnet in site 1 will see the broadcast as will the machines in site2 that are part of the extended vlan.