Monitoring - Step 1 of Visibility
- Tony Fortunato
- Feb 19, 2025
- 2 min read
In the packet world I hear a lot of concerns that when bandwidth increases, the ability to analyze is negatively impacted.
When I present or work on-site, I remind network technicians that network monitoring is the basis of developing a baseline of your network health which can be accomplished many ways.
You can get statistics directly from your network equipment, like good old SNMP/RMON, api's, telnet or ssh scripts and have the device report back to a centralized management system.
Regardless how you get the data, the important part of the process is to develop a process or procedure of how to interpet the data and what to do when you find an anomaly.
Heres a recent example, i was reviewing some of the traffic reports from a client's router when i noticed traffic on their standby link. I followed up with a simple packet trace and noticed a bunch of SSH login attempts.
When i showed the client, he was confused as to how that could happen because:
as part of their standard router configuration ssh is blocked from all WAN ports
since its a backup link, he didnt think the backup port was live 'on the net'
I went digging around the router configuration and for some reason this router interface was not included in the firewall rules. i spot checked about a dozen other routers and found another 4 more with the same misconfiguration which I quickly fixed.
I explained that just because you aren't actvely using the link, the interface would still be active 'on the net' with a valid IP address. Just because you arent going out doesn't mean no one can get in. I took it a step further and before making my firewall change, I typed the public IP of the backup link and logged in to that router.
I went to the network management system and showed him the traffic on the backup port before and after the firewall change.
The client asked how I 'knew' what to look for and how to fix the problem. i truthfully explained that I didn't 'know' or 'expect' anything, but the pattern on the backup link compared to the other routers looked 'odd', so I investigated.
The moral of the story is that having monitoring is good, but having a process or methodology to review the data is better.
we always look forward to hearing your feedback, article ideas or submissions from you.
