Route Sources – In-Depth Explanation

In routing, a route source refers to where or how a route to a destination network is learned by a router. Understanding route sources is fundamental for effective routing design and troubleshooting.

There are three primary route sources:

Connected Routes
Static Routes
Dynamic Routes

✅ Route Sources – Concept Checklist

Route Source	How Learned	Admin Distance (Default)	Metric Use	Manual Config	Example Protocols
Connected	Interface up with IP	0	Not needed	❌ No	N/A
Static	Manually configured	1	Optional	✅ Yes	N/A
Dynamic	Learned via protocols	Varies	✅ Yes	✅ Yes	RIP, OSPF, EIGRP

🔹 1. Connected Routes

🔸 Definition

A connected route is automatically added to the routing table when a router interface is configured with an IP address and is up.

🔸 Example

interface GigabitEthernet0/0
 ip address 192.168.10.1 255.255.255.0

This adds: C 192.168.10.0/24 is directly connected, GigabitEthernet0/0

🔸 Administrative Distance

AD = 0 (Most preferred)

🔸 Impact of Interface Status

Up = route appears
Down = route removed

🔸 Connected Routes in Static/Dynamic Routing

ip route 10.0.0.0 255.255.255.0 192.168.10.2

🔹 2. Static Routes

🔸 Definition

Manually configured paths using next-hop IP or exit interface.

🔸 AD = 1

🔸 Examples

ip route 10.0.0.0 255.255.255.0 192.168.1.2
ip route 10.0.0.0 255.255.255.0 GigabitEthernet0/1
ip route 10.0.0.0 255.255.255.0 192.168.1.2 GigabitEthernet0/1

🔸 Floating Static Route

ip route 10.0.0.0 255.255.255.0 192.168.1.2 5

🔸 Comparison

Method	Use Case	Pros	Cons
Next-hop IP	Multi-access	ARP handling	Needs ARP
Interface only	Point-to-point	Fast lookup	Broadcast issues
Fully specified	Best control	Clarity	Complex config

🔹 3. Dynamic Routes

🔸 Definition

Routes learned automatically through routing protocols.

🔸 Examples

RIP – Hop count
OSPF – Cost
EIGRP – Bandwidth + delay
BGP – Policy

🔸 AD Values

Protocol	AD
EIGRP	90
OSPF	110
RIP	120
BGP (eBGP)	20
BGP (iBGP)	200

🔸 Benefits

Scalability
Redundancy
Adaptability

🔹 4. Comparative Understanding

Feature	Connected	Static	Dynamic
Config Needed	No	Yes	Yes
Admin Distance	0	1	90–120+
Learning Method	Interface up	Manual	Protocols
Scalability	Low	Low	High
Flexibility	None	Moderate	High
Convergence	Instant	Manual	Automatic

✅ Summary Table

Route Type	AD	Configurable?	Auto Failover	Scalable	Common Use
Connected	0	No	No	No	Base for dynamic, local
Static	1	Yes	Yes (floating)	No	Small networks, backup
Dynamic	90+	Yes	Yes	Yes	Large networks

Routing Route Sources Quiz

1. What is a connected route?

A. A route learned through a routing protocol B. A manually configured backup route C. A route learned from a remote router D. A route automatically added when an interface is up with an IP address

Correct answer is D. Connected routes are automatically added when an interface is up and configured with an IP.

2. What is the default administrative distance (AD) of a static route?

A. 0 B. 1 C. 90 D. 110

Correct answer is B. Static routes have a default AD of 1.

3. Which of the following routing protocols uses a hop count as its metric?

A. RIP B. OSPF C. EIGRP D. BGP

Correct answer is A. RIP uses hop count as its metric.

4. What is a floating static route?

A. A static route with a lower AD than dynamic routes B. A route learned dynamically that can be converted to static C. A static route with a higher AD used as a backup D. A static route with no AD value

Correct answer is C. Floating static routes have higher AD to act as backups.

5. Which command is used to verify routing table entries and their administrative distances?

A. show ip protocols B. show ip route C. show running-config D. show interfaces

Correct answer is B. 'show ip route' displays the routing table and AD values.

6. What is the default AD of OSPF?

A. 110 B. 90 C. 120 D. 200

Correct answer is A. OSPF’s default AD is 110.

7. What happens to connected routes when the interface goes down?

A. They remain in the routing table B. They are redistributed as static routes C. They are converted to dynamic routes D. They are removed from the routing table

Correct answer is D. Connected routes disappear if the interface goes down.

8. Which of the following routing protocols has the lowest default AD?

A. RIP B. OSPF C. eBGP (External BGP) D. iBGP (Internal BGP)

Correct answer is C. External BGP has an AD of 20, the lowest among dynamic protocols.

9. Which route source has the highest trustworthiness?

A. Static route B. Connected route C. Dynamic route D. Floating static route

Correct answer is B. Connected routes have AD 0 and highest trust.

10. Which of the following is NOT true about static routes?

A. They require manual configuration B. They always automatically update on link failure C. They have an AD of 1 by default D. They can be used for backup with higher AD

Correct answer is B. Static routes do NOT automatically update on link failure unless configured as floating routes.

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