ICMP: Network and Host Unreachable

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Trigger three ICMP errors and compare the replies.

Sign in and launch

First: Routing Between Subnets

Network

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ICMP: Network and Host Unreachable
R1 knows only its two connected subnets.
Open a console

1. Configure connectivity

PC1

ip 192.168.1.21/24 192.168.1.1
save

PC2

ip 192.168.2.21/24 192.168.2.1
save

PC1

ping 192.168.2.21

Confirm replies before testing errors.

2. Compare errors

Run these commands on PC1.

CommandExpected result
ping 10.10.10.10ICMP 3/0 — network unreachable
ping 192.168.2.99 -w 5000ICMP 3/1 — host unreachable
ping 192.168.2.21 -T 1ICMP 11/0 — TTL exceeded
ping 192.168.2.21 -T 2Successful ping
ping 192.168.1.99Local ARP failure, without ICMP

Allow 5 seconds for the remote .99: R1 first tries ARP. Compare the sender of each error.

Validation

Click "Check". Once all steps pass, click "End".