Each Syslog message contains a priority value. The priority value is enclosed within the characters < >. The priority value can be between 0 and 191 and consists of a Facility value and a Level value. Facility being the type of message, such as a kernel or mail message. And level being a severity level of the message.<\/p>\n
To calculate the priority value the following formula is used : Priority = Facility * 8 + Level<\/strong><\/p>\n So to determine the facility value of a syslog message we divide the priority value by 8. The remainder is the level value. Using the above example this would give us a facility of 17 (local1) and a level of 5 (notice).<\/p>\n
\nBelow is an example of the tcpdump syntax :<\/p>\n[root@logserver ~]# tcpdump -Xni eth0 port 514\r\ntcpdump: verbose output suppressed, use -v or -vv for full protocol decode\r\nlistening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes\r\n20:08:05.306002 IP 10.1.1.10.55595 > 10.1.1.1.514: length: 288\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0000:\u00a0 4500 013c 177d 0000 4011 4b06 0a01 0164\u00a0 E..<.}..@.K....d\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0010:\u00a0 0a01 01c9 d92b a2a2 0128 5f4b 3c31 3431\u00a0 .....+...(_K<141<\/strong>\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0020:\u00a0 3e6e 7335 6774 3a20 4e65 7453 6372 6565\u00a0 ><\/strong>ns5gt:.NetScree\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0030:\u00a0 6e20 6465 7669 6365 5f69 643d 6e73 3567\u00a0 n.device_id=ns5g\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0040:\u00a0 7420 205b 526f 6f74 5d73 7973 7465 6d2d\u00a0 t..[Root]system-\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0x0050:\u00a0 6e6f<\/pre>\n