1. RIP (Routing Information Protocol)
- Type: Distance-vector routing protocol.
- Key Metric: Hop Count (max: 15, beyond 15 = unreachable).
- Algorithm: Bellman-Ford.
- Updates: Sent every 30 seconds (slow convergence).
- Version: RIP v1 (no subnetting, classful), RIP v2 (subnetting, classless).
- Port: UDP 520.
- Main Feature: Easy to configure but not scalable (used for small networks).
- Limitations: High convergence time, no support for complex networks.
2. OSPF (Open Shortest Path First)
- Type: Link-state routing protocol.
- Key Metric: Cost (based on bandwidth).
- Algorithm: Dijkstra’s Shortest Path First (SPF).
- Updates: Only when changes occur (fast convergence).
- Hierarchical Design: Divides networks into areas (Area 0 = Backbone).
- Port: IP protocol 89.
- Features:
- Classless (supports subnetting).
- Multi-area design reduces overhead.
- Supports VLSM, authentication.
- Advantages: Highly scalable, faster convergence, suited for large networks.
- Key Terms:
- LSA: Link-State Advertisement.
- DR/BDR: Designated Router/Backup DR to reduce overhead.
3. BGP (Border Gateway Protocol)
- Type: Path-vector routing protocol.
- Purpose: Routing between Autonomous Systems (AS), i.e., internet-scale routing.
- Key Metric: Path attributes (e.g., AS-PATH, NEXT-HOP).
- Algorithm: Uses policies (not shortest path).
- Updates: Only when changes occur (very stable).
- Port: TCP 179.
- Key Terms:
- iBGP: Internal BGP (within an AS).
- eBGP: External BGP (between AS).
- AS: Autonomous System (e.g., an ISP).
- Advantages:
- Highly scalable.
- Provides policy-based routing (choose best route based on policy).
- Drawback: Complex to configure.
Quick Comparison Table
| Feature | RIP | OSPF | BGP |
|---|---|---|---|
| Type | Distance-vector | Link-state | Path-vector |
| Best for | Small networks | Enterprise networks | Internet-scale routing |
| Metric | Hop Count | Cost (Bandwidth-based) | Path Attributes |
| Updates | Periodic (30s) | Only on changes | Only on changes |
| Protocol Port | UDP 520 | IP protocol 89 | TCP 179 |
| Scalability | Low | High | Very High |
Super Quick Mnemonics
- RIP: “15 hops is all you RIP!” (small networks, max hop count).
- OSPF: “Open to all areas, costs bandwidth!” (multi-area, cost metric).
- BGP: “Biggest Global Protocol!” (internet-scale routing).
These notes will make it super simple to recall the core concepts during your IPBS IT Officer exam!