Types of Routing

Routing Overview
Static Routing
Dynamic Routing
RIP (Routing Information Protocol v3)
OSPF (Open Shortest Path First)
EIGRP (Enhanced Interior Gateway Routing Protocol)
Static vs. Dynamic Comparison
Protocol Comparison Table
Exercises

1. Routing Overview

Routing is broadly categorized into two main types:

                   +---------------------------------+
                   |           ROUTING                |
                   +----------+----------------------+
                              |
              +---------------+---------------+
              |                               |
        +-----+-----+                  +------+------+
        |  STATIC   |                  |   DYNAMIC   |
        |  ROUTING  |                  |   ROUTING   |
        +-----------+                  +------+-------+
                                              |
                        +---------------------+---------------------+
                        |                     |                     |
                    +---+---+           +-----+-----+         +----+----+
                    |  RIP  |           |   OSPF    |         |  EIGRP  |
                    |(v1/v2/|           |  (Link-   |         | (Cisco  |
                    |  v3)  |           |  State)   |         |Hybrid)  |
                    +-------+           +-----------+         +---------+

Interior vs. Exterior Routing

Distinguishing routing inside an organization (IGP) versus between organizations (EGP).

Type	Scope	Protocols
IGP (Interior Gateway Protocol)	Inside one organization / AS	RIP, OSPF, EIGRP
EGP (Exterior Gateway Protocol)	Between different organizations	BGP (Border Gateway Protocol)

2. Static Routing

What is Static Routing?

Static routing uses routes that are manually configured by a network administrator. The router does not discover these routes -- they are fixed entries in the routing table.

How Static Routing Works

+--------------------------------------------------+
|  Administrator types:                            |
|  ip route 192.168.2.0 255.255.255.0 10.0.0.2     |
|                                                  |
|  Router adds entry to routing table:             |
|  S   192.168.2.0/24 [1/0] via 10.0.0.2           |
|       ^ Static marker     ^ AD/Metric            |
+--------------------------------------------------+

Advantages of Static Routing

Benefits of using static routing in a network.

Advantage	Explanation
No overhead	No routing protocol = no bandwidth used for updates
Secure	No advertisements = harder to attack
Predictable	Routes never change unless manually updated
Low resource	Minimal CPU/RAM usage on router
Simple	Easy to configure in small networks

Disadvantages of Static Routing

Limitations and drawbacks of static routing.

Disadvantage	Explanation
No fault tolerance	If a link fails, the static route breaks unless manually fixed
Manual effort	Every route must be typed in by hand
Not scalable	In a network with 100+ routers, static routing becomes unmanageable
Human error prone	Typing mistakes can cause outages

When to Use Static Routing

Scenarios where static routing is the best choice over dynamic protocols.

Small networks (< 5 routers)
Stub networks (networks with only one exit path)
Default routes (pointing to the internet)
Security-critical paths (where you want explicit control)
Backup links (floating static routes)

Floating Static Route (Backup)

A static route with higher administrative distance, used only when the primary route is unavailable.

A floating static route is a backup that only activates when the primary route fails:

Primary:   ip route 10.0.0.0/24 172.16.0.2          (AD = 1)
Backup:    ip route 10.0.0.0/24 172.16.1.2 10       (AD = 10)
                                          ^ Higher AD = backup

Static Route Configuration Examples

Linux

ip route add 192.168.2.0/24 via 10.0.0.2 dev eth0

Cisco IOS

ip route 192.168.2.0 255.255.255.0 10.0.0.2

Windows

route add 192.168.2.0 mask 255.255.255.0 10.0.0.2

3. Dynamic Routing

What is Dynamic Routing?

Dynamic routing uses routing protocols that automatically discover and share network information. Routers exchange updates and build routing tables without manual intervention.

How Dynamic Routing Works

Routers form neighbor relationships and exchange routing information dynamically.

+----------+           +----------+           +----------+
| Router A |---Hello-->| Router B |<--Hello---| Router C |
|          |<--Update--|          |---Update--|          |
+----------+           +----------+           +----------+
     |                      |                      |
     v                      v                      v
+-------------+     +-------------+         +-------------+
|   Routing   |     |   Routing   |         |   Routing   |
|   Table     |     |   Table     |         |   Table     |
|  (built     |     |  (built     |         |  (built     |
|  from       |     |  from       |         |  from       |
|  updates)   |     |  updates)   |         |  updates)   |
+-------------+     +-------------+         +-------------+

Advantages of Dynamic Routing

Benefits of using dynamic routing protocols.

Advantage	Explanation
Auto-failover	Routes update automatically when links fail
Scalable	Works in networks with hundreds of routers
Low maintenance	No manual route entries needed
Adaptive	Can choose the best path based on current conditions

Disadvantages of Dynamic Routing

Drawbacks of dynamic routing protocols.

Disadvantage	Explanation
Overhead	Protocol messages consume bandwidth and CPU
Convergence time	Takes time for all routers to agree after a change
Security exposure	Route advertisements can be intercepted/spoofed
Complexity	Requires understanding of protocol configuration

Types of Dynamic Routing Protocols

Classification of dynamic routing into Distance Vector, Link State, and Hybrid.

DYNAMIC ROUTING PROTOCOLS
|
+-- DISTANCE VECTOR
|   +-- RIP (v1, v2, v3)
|       +-- "I know the direction and distance"
|
+-- LINK STATE
|   +-- OSPF
|       +-- "I have a complete map of the network"
|
+-- HYBRID (Advanced Distance Vector)
    +-- EIGRP
        +-- "I know the best route and have backup info"

Key Dynamic Routing Concepts

Important terminology used across all dynamic routing protocols.

Term	Definition
Convergence	The time it takes for all routers to update their tables after a change
Routing Loop	Packets looping endlessly between routers
Hop Count	Number of routers a packet passes through
Metric	The cost/value used to compare routes
AD (Administrative Distance)	Trust level of the routing protocol

4. RIP (Routing Information Protocol v3)

RIP Protocol Overview

RIP is a distance vector protocol that routes based on hop count, best for small networks.

RIP is one of the oldest routing protocols. It's a Distance Vector protocol that uses hop count as its metric.

Property	Value
Type	Distance Vector
Metric	Hop Count (max 15)
AD	120
Port	UDP 520 (v1/v2), UDP 521 (v3)
Update Interval	30 seconds
Convergence	Slow (minutes)
Best for	Small networks

How RIP Works

Router A --- Router B --- Router C --- Router D
Network X                        Network Y

Each router tells its neighbors:
+-----------------------------------------------------+
| Every 30 seconds:                                    |
| "Hey neighbor! Here's my routing table..."           |
|                                                      |
| Router B tells Router A:                             |
|   I know how to reach Network Y (2 hops away)        |
|                                                      |
| Router A adds route:                                 |
|   Network Y -> via Router B -> 3 hops                |
+-----------------------------------------------------+

RIP Hop Count Limit

RIP cannot route across more than 15 hops — a fundamental limitation.

                    +-----+     +-----+     +-----+
--> R1 --> R2 --> R3 --> R4 --> R5 --> R6 --> R7 --> R8 --> ...
   1      2      3      4      5      6      7      8
                                                      ^
                                             Hop > 15 = UNREACHABLE

Important: RIP considers any route with a hop count of 16 or more as unreachable. This limits RIP to small networks.

RIP Versions

Comparison of features across RIP version 1, 2, and 3 (RIPng for IPv6).

Feature	v1	v2	v3
Classful/Classless	Classful	Classless (CIDR)	Classless (CIDR)
Subnet Masks	No	Yes	Yes
Authentication	No	Yes	Yes
IPv6 Support	No	No	Yes
Multicast	Broadcast (255.255.255.255)	Multicast (224.0.0.9)	Multicast (FF02::9)

RIP Configuration

router rip
 version 2
 network 10.0.0.0
 network 172.16.0.0
 no auto-summary

RIP Timers

Time intervals that control how RIP updates, invalidates, and removes routes.

Timer	Default	Purpose
Update	30s	How often routes are advertised
Invalid	180s	Time before a route is marked invalid (if no update received)
Holddown	180s	Time to ignore better routes after an update
Flush	240s	Time before a route is removed from the table

5. OSPF (Open Shortest Path First)

OSPF Protocol Overview

OSPF is a link-state protocol that uses cost based on bandwidth for path selection.

OSPF is a Link State routing protocol that builds a complete map (LSDB) of the network and uses SPF (Dijkstra's Algorithm) to calculate the shortest path.

Property	Value
Type	Link State
Metric	Cost (based on bandwidth: 10^8 / bandwidth)
AD	110
Protocol	IP (89)
Convergence	Fast (seconds)
Hierarchical	Yes (Areas)
VLSM/CIDR	Yes
Best for	Large networks

How OSPF Works

Phase 1: Discover Neighbors
+-----------------------------------------------+
| Router sends HELLO packets every 10 seconds    |
| Neighbors respond -> adjacency formed          |
|                                                |
|  R1 --HELLO--> R2                              |
|  R1 <--HELLO-- R2                              |
|           Adjacent!                            |
+-----------------------------------------------+

Phase 2: Exchange Link State Advertisements (LSAs)
+-----------------------------------------------+
| Each router tells its neighbors about its      |
| directly connected links.                      |
|                                                |
| R1: "I have 10.0.0.0/24"                       |
| R2: "I have 172.16.0.0/24 and 192.168.0.0/24"  |
| R3: "I have 192.168.0.0/24"                    |
+-----------------------------------------------+

Phase 3: Build LSDB & Run SPF
+-----------------------------------------------+
| All routers have the SAME Link State Database |
|                                               |
|  +------+                                     |
|  | R1   |---10.0.0.0---+                      |
|  +------+              |                      |
|                        |                      |
|                   +----+----+                 |
|                   |   R2    |---172.16.0.0--- |
|                   +---------+                 |
|                        |                      |
|                   +----+----+                 |
|                   |   R3    |                 |
|                   +---------+                 |
|                                               |
| Each router runs Dijkstra's SPF algorithm     |
| -> Calculates shortest path tree              |
| -> Populates routing table                    |
+-----------------------------------------------+

OSPF Areas

Logical divisions in OSPF that reduce routing table size and isolate network changes.

OSPF uses a hierarchical design with areas to reduce computation and routing table size.

+--------------------------------------------------+
|                   BACKBONE                       |
|                  AREA 0                          |
|  +----------+  +----------+  +----------+        |
|  |   ABR    |  |   ABR    |  |   ABR    |        |
|  +----+-----+  +----+-----+  +----+-----+        |
|       |              |              |            |
|  +----+-----+  +----+-----+  +----+-----+        |
|  | AREA 1   |  | AREA 2   |  | AREA 3   |        |
|  | (STUB)   |  | (NORMAL) |  | (NSSA)   |        |
|  +----------+  +----------+  +----------+        |
+--------------------------------------------------+

Area Type	Description
Area 0 (Backbone)	All areas must connect to this
Standard Area	Normal area with full LSDB
Stub Area	Blocks external routes (reduces table size)
Totally Stubby	Blocks external + inter-area (except default)
NSSA	Like stub but allows limited external routes

OSPF Cost Calculation

OSPF uses interface bandwidth to calculate path cost — lower cost means better path.

Cost = Reference Bandwidth / Interface Bandwidth
      (Reference = 100 Mbps by default)

Interface     Bandwidth    Cost
Gigabit       1000 Mbps    100/1000 = 1
Fast Ethernet  100 Mbps    100/100 = 1
Ethernet        10 Mbps    100/10 = 10
T1             1.544 Mbps  100/1.544 ~ 64
DSL/56K        0.056 Mbps  100/0.056 ~ 1785

Modern networks often change the reference bandwidth: auto-cost reference-bandwidth 100000 (for 100 Gbps)

OSPF Configuration

router ospf 1
 router-id 1.1.1.1
 network 10.0.0.0 0.255.255.255 area 0
 network 172.16.0.0 0.0.0.255 area 1
 auto-cost reference-bandwidth 10000

interface eth0
 ip ospf cost 10      ! Manually set cost (overrides auto)

OSPF Neighbor States

The sequence of stages two OSPF routers go through to form an adjacency.

DOWN --> ATTEMPT/INIT --> 2-WAY --> EXSTART --> EXCHANGE --> LOADING --> FULL
   |          |              |                                            |
   +----------+--------------+--------------------------------------------+
                           |
                     DR/BDR Election occurs here
                     (on multi-access networks)

OSPF Router Types

Different roles a router can have in an OSPF network based on its position and function.

Router Type	Role
Internal Router	All interfaces in one area
ABR (Area Border Router)	Connects two or more areas
ASBR (Autonomous System Boundary Router)	Connects OSPF to another routing protocol
Backbone Router	Has at least one interface in Area 0

6. EIGRP (Enhanced Interior Gateway Routing Protocol)

EIGRP Protocol Overview

EIGRP is an advanced distance vector protocol with fast convergence and backup routes.

EIGRP is Cisco's proprietary hybrid routing protocol -- combining the best of distance vector and link state. It's often called an Advanced Distance Vector protocol.

Property	Value
Type	Advanced Distance Vector (Hybrid)
Metric	Composite (bandwidth + delay + load + reliability)
AD	90 (internal) / 170 (external)
Protocol	IP (88)
Convergence	Very fast (instant backup routes)
VLSM/CIDR	Yes
Best for	Cisco-only medium-large networks

How EIGRP Works

1. Neighbor Discovery

R1 --HELLO--> R2  (multicast 224.0.0.10, every 5 seconds)
R1 <--HELLO-- R2
        Neighbors

2. Route Exchange (Full Update at Start)

R1 sends full routing table to R2 (only once)
Subsequent updates are PARTIAL (only changes)

3. DUAL Algorithm

EIGRP uses the Diffusing Update Algorithm (DUAL) for loop-free path selection.

EIGRP Composite Metric

EIGRP calculates route cost using bandwidth, delay, load, and reliability with adjustable K-values.

Metric = [K1 * BW + (K2 * BW) / (256 - Load) + K3 * Delay] * 256

Default K-values:
  K1 = 1 (Bandwidth)
  K2 = 0 (Load)
  K3 = 1 (Delay)
  K4 = 0 (Reliability)
  K5 = 0 (MTU)

Simplified Default Formula:
Metric = (Bandwidth + Delay) * 256

EIGRP Key Concepts

Important terms unique to EIGRP's DUAL algorithm and topology table.

Term	Definition
FD (Feasible Distance)	Best metric to a destination
AD (Advertised Distance)	Metric reported by the neighbor
FS (Feasibility Condition)	Neighbor's AD < our FD
Successor	Primary route (lowest FD)
Feasible Successor	Backup route (meets feasibility condition)
Topology Table	All routes learned from neighbors
Route States	Passive (stable) / Active (recalculating)

EIGRP Topology Table Example

+-------------------------------------------------------------+
|  Topology Table for 192.168.1.0/24                          |
|                                                             |
|  P - Passive (stable)                                       |
|                                                             |
|  P 192.168.1.0/24, 1 successors, FD is 28160                |
|     via 172.16.0.2 (28160/2560), eth0  <- SUCCESSOR         |
|     via 172.16.1.2 (30720/5120), eth1  <- FEASIBLE SUCCESSOR|
|                                            (backup)         |
+-------------------------------------------------------------+

The backup (Feasible Successor) is instant -- no convergence time if the primary fails!

EIGRP Configuration (Cisco)

router eigrp 100
 network 10.0.0.0
 network 172.16.0.0
 no auto-summary

EIGRP Tables

EIGRP uses three separate databases — Neighbor, Topology, and Routing tables.

EIGRP maintains three separate tables:

+-----------------+
| NEIGHBOR TABLE  |  --  "Who am I talking to?"
|                 |
| Neighbor  IP    |
| R2        10.0.0.2|
| R3        10.0.0.3|
+-----------------+
        |
        v
+-----------------+
| TOPOLOGY TABLE  |  --  "What do I know?"
|                 |
| Dest     FD   AD|
| 192.168.1.0     |
|   via R2   ...  |
|   via R3   ...  |
+-----------------+
        |
        v
+-----------------+
| ROUTING TABLE   |  --  "Which path am I using?"
|                 |
| Only successors |
| (best routes)   |
+-----------------+

7. Static vs. Dynamic Comparison

Factor	Static Routing	Dynamic Routing
Configuration	Manual	Automatic via protocol
Scalability	Poor (small networks only)	Excellent (any size)
Security	High (no advertisements)	Lower (protocols can be attacked)
Bandwidth Usage	None	Uses bandwidth for updates
CPU/RAM Usage	Minimal	Higher
Fault Tolerance	None (unless floating static)	Automatic failover
Predictability	Fully predictable	Depends on network state
Convergence	Instant (no change)	Varies (seconds to minutes)
Complexity	Low	Medium to High
Best For	Small/Stub/Default routes	Medium to large networks

Which One Should You Use?

Is the network small (2-5 routers)?     --> Static
Is there only one path to the internet? --> Static
Is it a stub network?                    --> Static
Do you need absolute control?            --> Static

Is the network large?                    --> Dynamic
Do you need automatic failover?          --> Dynamic
Is it growing / changing often?          --> Dynamic
Multiple paths between locations?        --> Dynamic (OSPF/EIGRP)

Many networks use both: Static for default routes and stub networks, Dynamic (OSPF/EIGRP) for the internal core.

8. Protocol Comparison Table

Feature	RIP	OSPF	EIGRP
Type	Distance Vector	Link State	Advanced DV
Metric	Hop Count	Cost (Bandwidth)	Composite (BW+Delay)
Max Hop Count	15	Unlimited	Unlimited
Convergence	Slow	Fast	Very Fast
AD	120	110	90 / 170
VLSM/CIDR	v2/v3	Yes	Yes
IPv6	v3	Yes	Yes
Hierarchical	No	Yes (Areas)	No (but supports summarization)
Authentication	v2/v3	Yes	Yes
Load Balancing	Equal-cost	Equal-cost	Unequal-cost (variance)
Update Type	Full table every 30s	Triggered (LSA)	Partial/Triggered
Vendor	Standard	Standard	Cisco (now open standard)
Scalability	Small	Large	Medium-Large
CPU Intensive	No	Yes (SPF recalc)	Moderate

Decision Flowchart

                    Which protocol to use?
                            |
                +-----------+-----------+
                |                       |
            Small net?            Large net?
                |                       |
                v                       v
         +------------+         +------------------+
         |    RIP     |         |  Cisco or Mixed?  |
         +------------+         +--------+---------+
                                         |
                           +-------------+-------------+
                           |                           |
                        Cisco?                    Mixed/Vendor-neutral
                           |                           |
                           v                           v
                     +----------+               +----------+
                     |  EIGRP   |               |   OSPF   |
                     +----------+               +----------+

9. Exercises

Exercise 1: Protocol Selection Scenarios

Scenario

You are a network consultant. For each scenario below, recommend the best routing protocol (or static routing) and justify your choice.

Factor	Scenario A	Scenario B	Scenario C	Scenario D	Scenario E
Network size	3 routers	50 routers	200 routers	20 routers	10 routers
Vendor	Cisco-only	Mixed	Mixed	Cisco-only	Mixed
Bandwidth	Low (T1)	High (10G)	Mixed	High (1G)	Low (DSL)
Staff skill	Low (junior)	Medium	Expert	Medium	Low
Convergence need	Not critical	< 10 sec	< 5 sec	Instant	Not critical
Budget	Minimal	Moderate	High	Moderate	Minimal
Future growth	None	2x in 2 years	3x in 5 years	50% growth	None

Questions

For each scenario (A through E), recommend one of: Static, RIP, OSPF, or EIGRP
Explain your reasoning in 2-3 sentences per scenario
For scenario E, could you use a default route only? Why or why not?

Click for Answers

Scenario A -- Static Routing

Only 3 routers, low bandwidth, minimal budget, junior staff
Static routing has zero overhead and is simple to configure
No convergence needed in a small, stable network
RIP could work but would waste bandwidth with 30s updates

Scenario B -- OSPF

50 routers, mixed vendor, fast convergence required
OSPF is vendor-neutral and converges in seconds
Link-state protocol works well in large, high-bandwidth networks
EIGRP is Cisco-proprietary (historically); RIP is too slow

Scenario C -- OSPF

200 routers is a prime candidate for OSPF's hierarchical design
Areas (Area 0 + sub-areas) reduce routing table size and SPF computation
Expert staff can tune OSPF parameters effectively
EIGRP would work but Cisco-only is not guaranteed (mixed vendor)

Scenario D -- EIGRP

Cisco-only network with 20 routers, fast convergence needed
EIGRP provides instant failover via Feasible Successors
Unequal-cost load balancing (variance) optimizes bandwidth usage
OSPF would also work but EIGRP converges faster

Scenario E -- Static Routing

Small network (10 routers), low budget, low skill, no growth
Minimal DSL bandwidth -- routing protocol overhead hurts performance
A default route can work if all traffic goes to one ISP
If there's only one internet exit, each site just needs a default route + static routes for internal networks
Static routing keeps it simple and cost-effective

Exercise 2: OSPF Cost Calculation & Path Selection

Scenario

You have four routers connected in a mesh topology. All links are Gigabit Ethernet (1000 Mbps).

                        +------+
                +-------| R1   |--------+
                |       +------+        |
                | 10.0.0.0/30     | 10.0.1.0/30
                |                       |
           +----+-----+           +-----+----+
           |   R2      |           |   R3     |
           +----+-----+           +-----+----+
                | 10.0.2.0/30           | 10.0.3.0/30
                |                       |
                +-----------+-----------+
                            |
                       +----+----+
                       |   R4    |
                       +---------+

Link Details

Link	Network	Connected	Speed
R1-R2	10.0.0.0/30	R1 eth0, R2 eth0	1000 Mbps
R1-R3	10.0.1.0/30	R1 eth1, R3 eth0	1000 Mbps
R2-R4	10.0.2.0/30	R2 eth1, R4 eth0	100 Mbps
R3-R4	10.0.3.0/30	R3 eth1, R4 eth1	10 Mbps

Additional attached networks:

R2: 192.168.1.0/24 (eth2)
R3: 192.168.2.0/24 (eth2)
R4: 192.168.3.0/24 (eth2)

OSPF reference bandwidth = 100 Mbps (default).

Tasks

Task A: Calculate the OSPF cost for each link:

R1-R2 (1000 Mbps)
R1-R3 (1000 Mbps)
R2-R4 (100 Mbps)
R3-R4 (10 Mbps)

Task B: What is the shortest path cost from R1 to each destination:

192.168.1.0/24
192.168.2.0/24
192.168.3.0/24

Task C: Traffic reaches R4 from R1 -- which path does OSPF choose and why?

Task D (Challenge): If you change the OSPF reference bandwidth to 10000 Mbps (10 Gbps):

Recalculate all link costs
Does the path from R1 to R4 change? Why or why not?

Task E: If R2 advertises 192.168.1.0/24 with a manually configured cost of 50, how does this affect routing from R1?

Click for Answers

Task A -- Link Costs (Reference = 100 Mbps)

Link	Speed	Calculation	Cost
R1-R2	1000 Mbps	100 / 1000 = 0.1 -> 1 (minimum)	1
R1-R3	1000 Mbps	100 / 1000 = 0.1 -> 1 (minimum)	1
R2-R4	100 Mbps	100 / 100 = 1	1
R3-R4	10 Mbps	100 / 10 = 10	10

Task B -- Shortest Path Costs from R1

Destination	Possible Paths	Best Path	Total Cost
192.168.1.0/24	R1->R2 (direct)	R1->R2	1
192.168.2.0/24	R1->R3 (direct)	R1->R3	1
192.168.3.0/24	R1->R2->R4 = 1+1 = 2
	R1->R3->R4 = 1+10 = 11
	Best: R1->R2->R4	2

Task C -- R1 to R4 Path

OSPF chooses: R1 -> R2 -> R4
Total cost = 1 (R1-R2) + 1 (R2-R4) = 2
The alternative R1 -> R3 -> R4 costs 1 + 10 = 11
Even though R2-R4 is 100 Mbps (slower than R2-R3), the R3-R4 link at 10 Mbps is the bottleneck
OSPF picks the cumulative lowest cost, not the fewest hops

Task D -- Reference Bandwidth Changed to 10000 Mbps

Link	Speed	New Calculation	New Cost
R1-R2	1000 Mbps	10000 / 1000 = 10	10
R1-R3	1000 Mbps	10000 / 1000 = 10	10
R2-R4	100 Mbps	10000 / 100 = 100	100
R3-R4	10 Mbps	10000 / 10 = 1000	1000

Path to R4 via R2: cost = 10 + 100 = 110
Path to R4 via R3: cost = 10 + 1000 = 1010
Path does NOT change -- R1->R2->R4 is still better
The ratio between link speeds stays the same, just scaled up
Cost is relative -- changing reference bandwidth mainly helps distinguish very fast links (e.g., 1 Gbps vs 10 Gbps both cost 1 at default reference)

Task E -- Manual Cost Override on R2

R2 sets cost to 50 for 192.168.1.0/24
R1 calculates: R1->R2 path to 192.168.1.0/24 = cost 1 (link) + 50 (advertised) = 51
If R3 also has a path to 192.168.1.0/24 with lower total cost, R1 will prefer that path instead
This allows administrators to influence routing decisions without changing physical topology
Common use: make a link preferred even if it's physically longer/the other path is faster

Types of Routing Protocols — A Complete Comparison: Static vs. Dynamic Routing, Distance Vector (RIP v3), Link State (OSPF), and Hybrid (EIGRP) Protocols with Configuration Examples

Table of Contents

1. Routing Overview

Interior vs. Exterior Routing

2. Static Routing

What is Static Routing?

How Static Routing Works

Advantages of Static Routing

Disadvantages of Static Routing

When to Use Static Routing

Floating Static Route (Backup)

Static Route Configuration Examples

Linux

Cisco IOS

Windows

3. Dynamic Routing

What is Dynamic Routing?

How Dynamic Routing Works

Advantages of Dynamic Routing

Disadvantages of Dynamic Routing

Types of Dynamic Routing Protocols

Key Dynamic Routing Concepts

4. RIP (Routing Information Protocol v3)

RIP Protocol Overview

How RIP Works

RIP Hop Count Limit

RIP Versions

RIP Configuration

RIP Timers

5. OSPF (Open Shortest Path First)

OSPF Protocol Overview

How OSPF Works

OSPF Areas

OSPF Cost Calculation

OSPF Configuration

OSPF Neighbor States

OSPF Router Types

6. EIGRP (Enhanced Interior Gateway Routing Protocol)

EIGRP Protocol Overview

How EIGRP Works

1. Neighbor Discovery

2. Route Exchange (Full Update at Start)

3. DUAL Algorithm

EIGRP Composite Metric

EIGRP Key Concepts

EIGRP Topology Table Example

EIGRP Configuration (Cisco)

EIGRP Tables

7. Static vs. Dynamic Comparison

Which One Should You Use?

8. Protocol Comparison Table

Decision Flowchart

9. Exercises

Exercise 1: Protocol Selection Scenarios

Scenario

Questions

Exercise 2: OSPF Cost Calculation & Path Selection

Scenario

Link Details

Tasks

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