Study Tables
Log message severity levels
| Keyword | Severity | Description | Mnemonic |
|---|---|---|---|
| Emergency | 0 | System unusable | Even |
| Alert | 1 | Immediate action required | A |
| Critical | 2 | Critical Event (Highest of 3) | Computer |
| Error | 3 | Error Event (Middle of 3) | Expert |
| Warning | 4 | Warning Event (Lowest of 3) | Will |
| Notification | 5 | Normal, More Important | Not |
| Informational | 6 | Normal, Less Important | Ignore |
| Debug | 7 | Requested by User Debug | Debugs |
Mnemonic courtesy of Romelchand
IP protocol numbers
When IP encapsulates another protocol it labels the protocol field with a number to define the next layer.
| IP Protocol Number | Description |
|---|---|
| 1 | ICMP |
| 2 | IGMP |
| 6 | TCP |
| 17 | UDP |
| 46 | RSVP |
| 47 | GRE |
| 51 | ESP (IPSec) |
| 51 | AH (IPSec) |
| 69 | TFTP |
| 88 | EIGRP |
| 89 | OSPF |
| 103 | PIM |
| 112 | VRRP |
| 115 | L2TP |
| 161 | SNMP |
| 162 | TRAPS |