Appendix – What Just Happened® Reasons
| Category | Name | Description | Severity | 
| Ethernet | Ingress Packet Reserved DMAC | Destination MAC is Reserved (DMAC=01-80-C2-00-00-0x) | Notice | 
| Ethernet | Ingress Switch Vtag Allow | VLAN tagging mismatch | Notice | 
| Ethernet | Ingress Switch VLAN | VLAN filtering | Notice | 
| Ethernet | Ingress Switch STP | Ingress spanning tree filter | Notice | 
| Ethernet | Lookup Switch UC | Unicast FDB discard | Notice | 
| Ethernet | Lookup Switch MC Null | Multicast list is empty | Notice | 
| Ethernet | Lookup Switch LB | Port loopback filter | Notice | 
| Ethernet | Ingress Packet SMAC is MC | Source MAC is multicast | Notice | 
| Ethernet | Ingress Packet SMAC Equals DMAC | Source MAC equals destination MAC | Notice | 
| IP | Ingress Router No HDR | Non IP packet | Notice | 
| IP | Ingress Router UC DIP MC DMAC | Unicast destination IP but non-unicast destination MAC | Notice | 
| IP | Ingress Router DIP LB | Destination IP is loopback address | Notice | 
| IP | Ingress Router SIP MC | Source IP is multicast | Notice | 
| IP | Ingress Router SIP Class E | Source IP is in class E | Notice | 
| IP | Ingress Router SIP LB | Source IP is loopback | Notice | 
| IP | Ingress Router SIP Unspecified | Source IP is not specified | Notice | 
| IP | Ingress Router IP HDR | Checksum or IPver or IPv4 IHL too short | Notice | 
| IP | Ingress Router MC DMAC | Multicast MAC mismatch | Notice | 
| IP | Ingress Router SIP Equals DIP | Source IP equals to destination IP | Notice | 
| IP | Ingress Router SIP BC | IPv4 source IP is limited broadcast | Notice | 
| IP | Ingress Router DIP Local Network | IPv4 destination IP is local network | Notice | 
| IP | Ingress Router DIP Link Local | IPv4 destination IP is link local | Notice | 
| IP | Router IRIF Disabled | Ingress IP interface is disabled | Notice | 
| IP | Router ERIF Disabled | Egress IP interface is disabled | Notice | 
| IP | Router LPM4 | IPv4 LPM unicast miss | Notice | 
| IP | Router LPM6 | IPv6 LPM unicast miss | Notice | 
| IP | MC Scope IPv6 0 | IPv6 destination in multicast scope FFx0:/16 | Notice | 
| IP | MC Scope IPv6 1 | IPv6 destination in multicast scope FFx1:/16 | Notice | 
| Tunnel | Decapsulation Packet | Remained packet is too short | Notice | 
| Tunnel | Decapsulation Error | Decapsulation error | Notice | 
| Tunnel | Overlay Switch SMAC Multicast | Overlay: source MAC is multicast | Notice | 
| Tunnel | Overlay Switch SMAC Equals DMAC | Overlay: source MAC equals destination MAC | Notice |