Fact Sheet: Connectivity Issue Fast Resolution – How to make it happen?

Most of the times we face “Connectivity Issue”. By connectivity we mean a “Communication Failure ” between a sources and destination.

The very obvious conclusion at first step is that “There is a Network Issue”, since our definition of “connectivity” is most of the times synonymous with “network”.

 

Network is of course, may be one of the major reason of connectivity breakdown, but we should understand that the “Connectivity” can break at various layers.

Since “Connectivity” can break at any of the five layers of TCP/IP model, please refer following Table to understand connectivity.

Layer	Connectivity Metrics	What to check?	Who will check?
Application	Application Port	On Server check if “Port” for application is up or not.	First -> Application Team Second -> Server OS Team
Transport	Firewall Rules for Application Port	On Server and firewall, need to check if there is interested traffic passing or not.	First -> Server OS Team Second -> Firewall Team
Network	Routing done for Application/Server reachability	On Server and intermediate routers and switches check the gateways status and routing.	First -> Server OS Team Second -> Network Team Third -> Firewall Team
Data Link	Application/Server connectivity to local switch in DC.	Check the VLAN/Interface status in Server, switch and SVI status.	First -> Server Team Second -> Network Team
Physical	Cabling and NIC cards on both Server and Switch	Check the server NIC, Switch ports for traffic and errors.	First -> Server Team Second -> Network Team

There is always a “Technical Language Gap” across teams working on different technologies and domain. If we are ready and handy with the information, other team expects from us, we can rise above in converging to the root cause fast.