Looking for details on troubleshooting

Given a scenario where you have two routers, one in data centre X (US) and other in data centre Y (UK), and these data centres are connected via different ISP1 and ISP2.
R1 in DC X (US) ----- ISP1------Internet------ISP2-------R2 in DC Y (UK)
If I see some packet loss between R1 and R2, how can I troubleshoot it? What logs can I look at? What commands and tools can I use?

Hello Janhavi

For deployments of datacenters such as those that you describe, that sound like they’re mission-critical infrastructure for your enterprise, it’s always a good idea to deploy a network monitoring system (NMS) such as SolarWinds or LibreNMS (there are many MANY options out there). They have the tools necessary to monitor, record, and evaluate network behavior.

Now having said that, in your particular case, how do you troubleshoot packet loss? Well, first you have to identify where the packet loss is taking place. Is it in your own infrastructure? This is relatively easy to determine if you’re using an NMS. You will see some queues overflowing, an interface being oversubscribed, or some access lists that may be denying traffic. These are things that are “caught” by the NMS, and you can identify them.

If however the packet loss is taking place on the ISPs or somewhere in between, then that’s a bit more difficult. If the packets being sent out from the US datacenter don’t all reach the UK datacenter, then you should speak with your ISPs and coordinate your troubleshooting process with them. However, before you do so, you should gather additional information to share with the ISP. Some of that info should include:

  1. Under what circumstances do you see packet loss?
  2. Is it packets of a particular type/application/source or all packets in general?
  3. Does it occur in both directions or just one direction or both?

Once you get this information, it’s a good idea to talk with the ISPs. In such a case, getting the ISPs is necessary since the packet loss is not occurring on your network, but on theirs.

I hope this was a good first step to getting closer to resolving your issue. Keep us posted on how you get along, and if you have any other questions, let us know!

I hope this has been helpful!