The MSGNAME field of the HEADER uniquely identifies the message within the context of a given APPNAME. A fixed severity and logical meaning is associated with a specific MSGNAME within a specific APPNAME. In other words, the same message name cannot appear with different severity or a completely different logical meaning for the same APPNAME value even if the message is originated by a different process.
Message names are only unique within a given application (a given APPNAME value) unless the message is one of the standard messages. Thus, applications interpreting CiscoLog messages should be careful not to assume that a message with a given name has the same meaning for all applications that may use this message name. Indeed, if the message is not one of the standard messages, it may have a different severity and meaning in a different application.
The MSGNAME field must consist of at least two characters. Acceptable characters are limited to the following ASCII decimal values: 48-57 (numbers), 65-90 (upper-case letters) and 95 (underscore). While IOS allows lower-case letters as well, the vast majority of IOS messages use only the upper-case letters. In order to be consistent with established conventions we opted to restrict the character set to upper-case letters, numbers and underscore characters.
Both numeric-only or alphanumeric message names are acceptable. However, per IOS convention, it is recommended that a user-friendly alphanumeric label be preferred to a numeric-only label. For example, "NO_MEMORY" message name is preferred to a "341234" identifier.
A special tag mid is defined in the CiscoLog Standard Tags specification for identifying a numeric id corresponding to a message name. This tag can be used to provide a numeric message is in addition to the MSGNAME. When this tag is used, a given MSGNAME must always correspond to a single message id value. CiscoLog defines mid tag values for each standard message.
The length of the MSGNAME field must not exceed 30 characters, but most message names should be more concise. MSGNAME value may not conflict with the names defined in this standard.
A separate message name must be defined for each logically different message. In other words, while the message text for a given message name can vary by virtue of some substitutable parameters, logically different messages must have different message names.
The following is an example of correct use of message name:
11: host.cisco.com: Jun 13 2003 23:11:52.454 UTC: %BACC-4-CONNECTION_LOST: %[pname.orig=rdu]: Server lost connection to host [126.96.36.199]12: host.cisco.com: Jun 13 2003 23:11:52.458 UTC: %BACC-4-CONNECTION_LOST: %[pname.orig=rdu]: Server lost connection to host [188.8.131.52
Notice that while the IP address of the host changes, it is still logically the same type of message. The following is an example of an INCORRECT use of the message name:
15: host.cisco.com: Jun 13 2003 23:11:52.458 UTC: %BACC-4-CONNECTION: %[pname.orig=rdu]: Server lost connection to host [184.108.40.206]16: host.cisco.com: Jun 13 2003 23:11:52.468 UTC: %BACC-4-CONNECTION: %[pname.orig=rdu]: Server re-established connection to host [220.127.116.11]
The use of a single message name for two different events in the above example is wrong and unacceptable. This is referred to as a "catch-all" message name and they must be avoided. Another extreme example is defining a message named "ERROR" and providing all error log messages under the same message name. This defeats the purpose of having the message name field, which is to enable external filtering of messages or easily trigger actions.
The only exception to the "no-catch-all" rule is when message cannot be identified ahead of time with anything better than a generic description or the users will not benefit from distinguishing the various subtypes of the message.
Although some applications may choose to do so, there is generally no need to define a separate message name for all debugging messages because debugging messages are not intended for automated filtering and action triggering based on message name. The sheer number of debugging messages and the highly dynamic nature of what is produced in them makes it very hard to define separate messages.
This specification proposes establishing a mailing list that could be used by groups for consulting purposes when in doubt about how to define certain messages. Currently, the mailing list alias used for this purpose is "cmn-logging".