net_tech_notes Network Technology Note Summaries Packets Format Routing BGP BGP IPv6 BGP configuration example OSPF Security IPSec VPN Label MPLS MPLS VPN MPLS TE Linux Tools iperf shell IPtables DNS DHCP tcpdump Network Monitor cacti zabbix Others vPC QoS VxLAN Multicast Multicast UDLR IGMP Proxy hillstone command H3C VLAN Troubleshooting High CPU Utilization NetFlow Python Packet Learning IPy Packet