Monitoring

Check Firewall

• UDP

[ ~]$ nc -v -u -z -w 3 targethost 25826
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.168.1.2:25826.
Ncat: UDP packet sent successfully
Ncat: 1 bytes sent, 0 bytes received in 2.03 seconds.
[ ~]$ nc -v -u -z -w 3 targethost 25828
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.168.1.2:25828.
Ncat: Connection refused.

WAN monitoring - Ethernet OAM - Y.1731

• https://app.netrounds.com/static/2.26/support/task-types/refl/y1731-eth-slm.html
• https://www.cisco.com/c/en/us/support/docs/asynchronous-transfer-mode-atm/operation-administration-maintenance-oam/117457-technote-cfm-00.html
• https://www.juniper.net/documentation/en_US/junos/topics/topic-map/oam-service-overview.html

Essentially a formalised version of Cisco SAA probes You really want to use the two way delay probes but this requires hardware at both ends with accurate clocks and support for it.

LibreNMS

Generate an Alarm (aka re-raise it)

./test-alert.php -r 8 -d -h host

Validate Transport logic but doesnt send anything

./test-template.php -t 0 -h host -r 8 -d