When I started with DevOps, I focused on automation and scripting — but soon realized none of it mattered if systems couldn’t talk to each other. One broken route, a blocked port, or a misconfigured subnet could turn a perfect deployment into a dead service.
That’s when I decided to truly understand Networking, not as theory, but as the heartbeat of DevOps.
Computer Networking Overview
Networking is simply how systems communicate. But in DevOps, it’s the foundation of everything — from connecting CI/CD runners to Kubernetes pods.
Think of it like this:
Your code travels through the network pipeline to reach users.
If that pipeline breaks, your service disappears.
Lesson: In DevOps, networking isn’t optional knowledge - it’s your system’s lifeline.
OSI Model - My Troubleshooting Map
The OSI Model isn’t just textbook theory - it’s a structured way to debug real problems.
Layer --- Name ------ What I Check As DevOps
7 --- Application ------ Web servers, APIs, DNS, SSH
6 --- Presentation ------ SSL/TLS encryption
5 --- Session ------ Long-lived connections
4 --- Transport ------ TCP/UDP, ports
3 --- Network ------ IP routing, subnets
2 --- Data Link ------ MAC addressing, ARP
1 --- Physical ------ NICs, cables, virtual interfaces
Scenario:
Once, my SSH connection to an EC2 instance failed. Using OSI logic:
L3 (ping worked)
L4 (port 22 blocked by security group)
Lesson: OSI = The ultimate DevOps debugging checklist.
Cloud Networking - The Invisible Backbone
When I deployed my first multi-tier app on AWS, the frontend couldn’t talk to the backend.
Cause: The frontend was in a public subnet, backend in a private one, but I forgot to configure NAT Gateway for outbound access.
Fixed it by:
- Updating route tables
- Attaching a NAT gateway
Lesson: Cloud networking uses old principles with new names - VPC = LAN, NAT = router, SG = firewall.
LAN, Switch, Router, Subnet, Firewall, Gateway
Concept Purpose Real-World DevOps Example
LAN ----- Connects devices locally ----- Kubernetes cluster network
Switch ----- Connects nodes in LAN ----- Docker bridge network
Router ----- Routes traffic between networks ----- VPC internet gateway
Subnet ----- Segments network ----- Private and public subnets in AWS
Firewall ----- Controls access ------ Security groups, NACLs
Gateway ----- Network exit point ------- NAT Gateway for private instances
Real Scenario:
- Two Docker containers couldn’t reach each other - turned out they were on different bridge networks.
- Fixed it by connecting them to the same subnet.
Lesson: Understanding topology saves hours of debugging.
Microservices Networking - When Services Talk to Each Other
In a microservices world, everything talks - but not everything listens properly.
Incident:
payment-service couldn’t reach user-service.
Used:
kubectl exec -it payment-pod -- nslookup user-service
CoreDNS was down. Restarted it, and communication was restored.
Lesson: In Kubernetes, DNS = glue for microservices. If DNS breaks, your entire mesh collapses.
IP Addresses and Ports - The System’s Identity
An IP is your system’s address; a port is the specific door you knock on.
Service ---- Port ---- Protocol
SSH ---- 22 ---- TCP
HTTP ---- 80 ---- TCP
HTTPS ---- 443 ---- TCP
Jenkins ---- 8080 ---- TCP
MySQL ---- 3306 ---- TCP
Check open connections:
Lesson: Every port tells a story - know which ones your app uses, and why.
DNS - The Internet’s Phonebook
When you type google.com, your system asks a DNS server for the IP.
If DNS fails, even healthy servers look “down.”
Commands:
Scenario:
My app worked with IP but failed with the domain - misconfigured DNS record.
Lesson: DNS is invisible until it breaks - then it’s everything.
Useful Networking Commands Every DevOps Engineer Must Know
Command ------ Purpose
ping ------ Check connectivity
ifconfig / ip a ------ View interfaces
traceroute ------ Show packet path
arp -a ------ View MAC-to-IP mapping
iptables -L -n ------ Firewall rules
netstat -tuln ------ Active ports
route -n ------ Routing table
nslookup / dig ------ DNS resolution
curl -v ------ Test HTTP connections
These commands have saved me more times than I can count.
Real-World Turning Point
- During one deployment, everything looked green - yet users couldn’t reach the app.
- After hours of panic, I realized the service was configured as ClusterIP (internal-only) instead of LoadBalancer.
- One YAML change later, traffic started flowing.
Lesson: In DevOps, most “application outages” are actually network misconfigurations.
Key Takeaways
- Networking is the foundation of DevOps.
- OSI model = debugging GPS.
- Cloud networking = traditional concepts in fancy wrappers.
- DNS, IP, and ports define your app’s reachability.
- Always test with real tools (ping, curl, traceroute, netstat).
What’s Next (Day 8: Network Security & DevSecOps)
Now that I know how systems talk, the next step is learning how to protect that communication.
In Day 8, I’ll explore:
- Network Security Attacks (DDoS, MITM)
- Firewall & ACL configurations
- TLS/IPsec protocols
- DevSecOps tools for automated security
Top comments (2)
Great article
so helpfull 🙌