Directly Connected Networ

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What is a Directly Connected Network?

In networking, a directly connected network is a network that is immediately accessible through one of the router's interfaces, without the need to go through any other routers. This means:

• The router has an interface configured with an IP address that belongs to that network, and

• The router can communicate with devices in that network without routing through any other device.

How to Identify Directly Connected Networks (in your topology)

Let’s look at each router’s IP routing table and physical connections:

Router R1

R1#show ip route 
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     10.0.0.0/30 is subnetted, 1 subnets
C       10.0.0.0 is directly connected, Serial0/0/0
C    192.168.1.0/24 is directly connected, FastEthernet0/0
R1#

This means:

• R1 is directly connected to the 10.0.0.0/30 network via Serial0/0/0 (to R2).

• R1 is also directly connected to the 192.168.1.0/24 network via Fa0/1 (to Switch 1 and PCs).

Router R2

R2#show ip route 
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     10.0.0.0/30 is subnetted, 2 subnets
C       10.0.0.0 is directly connected, Serial0/0/0
C       10.0.0.4 is directly connected, Serial0/1/0
C    192.168.2.0/24 is directly connected, FastEthernet0/0
R2#

This means:

R2 has three directly connected networks:

• 10.0.0.0/30 via Serial0/0/0 (to R1)

• 10.0.0.4/30 via Serial0/1/0 (to R3)

• 192.168.2.0/24 via Fa0/1 (to Switch 2 and PCs)

Router R3

R3#show ip route 
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     10.0.0.0/30 is subnetted, 1 subnets
C       10.0.0.4 is directly connected, Serial0/1/0
C    192.168.3.0/24 is directly connected, FastEthernet0/0
R3#

This means:

R3 is directly connected to:

• 10.0.0.4/30 via Serial0/1/0 (to R2)

• 192.168.3.0/24 via Fa0/1 (to Switch 3 and PCs)

Key Logical Takeaways

1. Directly connected means the router has a leg (interface) in that network.

2. If a router interface is configured with an IP address from a subnet, that entire subnet is considered directly connected.

3. These routes appear automatically in the routing table with a "C" (Connected) label—no static or dynamic routing required.

4. A router can only communicate with other networks (not directly connected) via routing (static/dynamic), not automatically.

Cisco Packet Tracer (Version 6.2.0.0052)

11KB

directly-connected-network.pkt

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