1. Switch 1 Switch 2 Switch 3 Blocking Forwarding ROOT BRIDGE BRIDGE’S ROOT PORT DESIGNATED PORT DESIGNATED BRIDGE

2. ISL Header 26 Bytes Encapsulated Ethernet Frame ISL FCS 4 Bytes DA TypeUserSALENAAAA03HSAVLANBPDUINDEXRES ISL Header Dest Priority 802.1Q Header SrcTagLen/E typeDataFCS New Calculation VLAN-ID Original Ethernet Frame 4 Byte Tag Added

3. Switch 1 VLAN1 VLAN2 Switch 2 VLAN1 VLAN2 Trunk VLAN IDEthernet Frame

4. Switch 1 Switch 2 Switch 3 Discarding Forwarding ROOT BRIDGE BRIDGE’S ROOT PORT DESIGNATED PORT DESIGNATED RSTP ALTERNATE PORT Forwarding Discarding RSTP BACKUP PORT HUB

5. Dst: 10.10.10.10Dst: 30.30.30.1 Src: 10.10.10.10Dst: 40.40.40.1 Inside Local 10.10.10.10 NAT Src: 30.30.30.1Dst: 40.40.40.1 40.40.40.130.30.30.110.10.10.1 Src: 40.40.40.1Src: 40.40.40.1.1 Inside GlobalOutside Global Outside Local IP address assigned to the host in the private network IP address representing the outside host in the private network IP address representing the inside host on the external network IP address assigned to the host on the external network Local Global “Host A” pings “Router B” A B