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Monitored Prefixes List

Auto-generate prefixes list

To auto generate the monitored prefixes file (by default called prefixes.yml) execute:

  • If you are using the binary ./bgpalerter-linux-x64 generate -a ASN(S) -o OUTPUT_FILE (e.g. ./bgpalerter-linux-x64 generate -a 2914 -o prefixes.yml).
  • If you are using the source code npm run generate-prefixes -- --a ASN(S) --o OUTPUT_FILE (e.g. npm run generate-prefixes -- --a 2914 --o prefixes.yml).

The script will detect whatever is currently announced by the provided AS and will take this as "the expected status".

A warning will be triggered in case of not valid RPKI prefixes, anyway, you should always check the generated list, especially if you are using the option -i

Below the list of possible parameters. Remember to prepend them with a -- instead of - if you are using the source code version.

Parameter Description Expected format Example Required
-o The YAML output file A string ending in ".yml" prefixes.yml Yes
-a The AS number(s) you want to generate the list for A comma-separated list of integers 2914,3333 No (one among -a, -p, -l is required)
-e Prefixes to exclude from the list A comma-separated list of prefixes 165.254.255.0/24,192.147.168.0/24 No
-i Avoid monitoring delegated prefixes. If a more specific prefix is found and it results announced by an AS different from the one declared in -a, then set ignore: true and ignoreMorespecifics: true Nothing No
-p Prefixes for which the list will be generated A comma-separated list of prefixes 165.254.255.0/24,192.147.168.0/24 No (one among -a, -p, -l is required)
-l A file containing the prefixes for which the list will be generated A text file having a prefix for each line prefixes.txt No (one among -a, -p, -l is required)
-s A list of ASns to be monitored. See monitorASns for more information A comma separated list of integer 2914,3333 No
-m Monitor all ASns which are origin of at least one of the monitored prefixes. This option is the same of -s except that the list of ASns is automatically generated by detecting the origin AS of all the monitored prefixes. See monitorASns for more information Nothing No

Prefixes list fields

The prefix list is a file containing a series of blocks like the one below, one for each prefix to monitor.

Tip: Only the attributes description, asn, and ignoreMorespecifics are mandatory.

165.254.255.0/24:
  description: Rome peering
  asn: 2914
  ignoreMorespecifics: false
  ignore: false
  group: aUserGroup
  excludeMonitors:
    - withdrawal-detection
  path:
    match: ".*2194,1234$"
    notMatch: ".*5054.*"
    matchDescription: detected scrubbing center
    maxLength: 128
    minLength: 2

Tip: In yml, arrays of values are described with dashes, like below:

asn:
- 2914
- 3333

Below the complete list of attributes (the dot notation is used to represent yml sub-dictionaries):

Attribute Description Expected type Required
asn The expected origin AS(es) of the prefix An integer or an array of integers. Yes
description A description that will be reported in the alerts A string Yes
ignoreMorespecifics Prefixes more specific of the current one will be excluded from monitoring A boolean Yes
ignore Exclude the current prefix from monitoring. Useful when you are monitoring a prefix and you want to exclude a particular sub-prefix A boolean No
includeMonitors The list of monitors you want to run on this prefix. If this attribute is not declared, all monitors will be used. Not compatible with excludeMonitors. An array of strings (monitors name according to config.yml) No
excludeMonitors The list of monitors you want to exclude on this prefix. Not compatible with includeMonitors. Use monitors name attributes, as defined in the monitor listy in config.yml. An array of strings (monitors name according to config.yml) No
path A dictionary containing all sub-attributes for path matching. All the sub-attributes are in AND. Sub-attributes (as follows) No
path.match The regular expression that will be tested on each AS path. If the expression tests positive the BGP message triggers an alert. ASns are comma separated (see example above). Please, use optimized regular expression as described in the following sub-section A string (valid RegEx) No
path.notMatch The regular expression that will be tested on each AS path. If the expression tests positive the BGP message will not triggers an alert. ASns are comma separated (see example above). A string (valid RegEx) No
path.matchDescription The description that will be reported in the alert in case the regex test results in a match. A string No
path.maxLength The maximum length allowed for an AS path. Longer paths will trigger an alert. A number No
path.minLength The minimum length allowed for an AS path. Shorter paths will trigger an alert. A number No
group The name of the group that will receive alerts about this monitored prefix. By default all alerts are sent to the "default" group. See here. A string No

Options entry

Optionally the prefixes list can contain an options entry, such us:

options:
  monitorASns:
    2914:
      group: default

The options entry allows the configuration of additional monitoring options directly from the prefixes list file.

Option Description
monitorASns A dictionary of ASns to be monitored. Each entry of the dictionary has the ASn as key. Each value of the dictionary contains the monitoring settings.

monitorASns

Allows for generic monitoring (not related to specific prefixes) of Autonomous Systems.

An example of monitorASns configuration is:

monitorASns:
    2914:
      group: ntt
    3333:
      group: ripencc

The AS2914 and AS3333 will be monitored. The alerts related to AS2914 will be sent to the "ntt" user group and the alerts for AS3333 to the "ripencc" user group.

The monitor in charge of doing this type of detection is monitorAS (click for more information).

Optimized regular expressions for AS path matching

The following simple regular expressions will drastically reduce CPU and network usage when applied to the path.match attribute. Instead, there are no benefits in applying the following regular expressions to the path.notMatch attribute.

To drastically optimize the process, try to use one of the following regular expression for path.match attribute. If the obtained filter is too loose, add additional (complex) constraints in path.notMatch. In this way the more complex path.notMatch will be tested only on the subset produced by the faster path.match.

  • "789$" - match paths that originate with AS789
  • "456" - match any path that traverses AS456 at any point
  • "^123,456" - match paths where the last traversed ASns were 123 and 456 (in that order)
  • "^123,456,789$" - match the exact path [123, 457, 789]
  • "[789,101112]" - match paths containing the AS_SET {789, 101112}