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Aisalkyn Aidarova
Aisalkyn Aidarova

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LAB 1 — End-to-End Application + DNS + HTTP

Goal

Simulate a real application flow

What to build

  • Use your existing server

  • Turn ON:

    • HTTP service
    • DNS service

Steps

  1. On Server → Services → HTTP → ON
  2. Create DNS record: 
   app.local → 192.168.50.10
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  1. On PC → Desktop → Web Browser: 
   http://app.local
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What you demonstrate (SRE mindset)

  • DNS resolution
  • Application reachability
  • End-to-end flow: 
  DNS → Routing → HTTP
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🔥 LAB 2 — Failure Simulation (MOST IMPORTANT FOR SRE)

Goal

Break things and troubleshoot

Scenarios to test

❌ Scenario 1 — DNS failure

  • Turn OFF DNS service

Test:

ping app.local  → FAIL
ping 192.168.50.10 → WORKS
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👉 You prove:

  • Network works
  • DNS is the problem

❌ Scenario 2 — DHCP failure

  • Turn OFF DHCP

Test:

  • PC gets no IP

👉 You prove:

  • Infra dependency (DHCP is critical)

❌ Scenario 3 — VLAN mismatch

  • Change PC port to wrong VLAN

👉 Result:

  • No connectivity

❌ Scenario 4 — Remove ip helper-address

👉 Result:

  • DHCP fails across VLANs

What you demonstrate

👉 This is REAL SRE work:

  • isolate problem
  • layer-by-layer debugging

🔥 LAB 3 — Monitoring & Logs (Simulated)

Goal

Think like observability engineer

What to simulate

You don’t have real Prometheus in Packet Tracer, but you can simulate:

  • Continuous ping: 
  ping 192.168.50.10 -t
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  • Then break network:

    • shutdown interface
    • remove trunk

👉 Observe:

  • packet loss
  • downtime

What you explain (interview gold)

  • health checks
  • uptime monitoring
  • alerting concept

🔥 LAB 4 — Redundancy Concept (Important for SRE)

Goal

High availability thinking

Simulation

  • Add second server (192.168.50.11)
  • Create DNS: 
  app.local → 192.168.50.10
  app.local → 192.168.50.11
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👉 Simulate:

  • one server down
  • traffic still resolves

What you explain

  • load balancing (basic)
  • fault tolerance
  • HA design

🔥 LAB 5 — Security (Basic SRE)

Goal

Control traffic

Example

Block VLAN 10 from accessing server

On router:

access-list 100 deny ip 192.168.10.0 0.0.0.255 any
access-list 100 permit ip any any

interface g0/0.10
ip access-group 100 in
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What you demonstrate

  • network security
  • access control
  • isolation

🔥 LAB 6 — Real SRE Troubleshooting Scenario

Scenario

“User says: App is down”

Your process:

Step 1 

ping app.local
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Step 2 

ping 192.168.50.10
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Step 3

Check:

  • DHCP?
  • DNS?
  • Routing?
  • VLAN?
  • Server service?

What you show

👉 Structured debugging

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