Fix the duplex mismatch
Users say the network to router R1 is "slow and flaky". The link is up, yet pings lose packets. Someone recently "tuned" one of the ports by hand. Find the mismatch, prove it with the counters, and fix it the clean way, so both ends negotiate.
How it works: this is VulnTech NetLab, a network simulator running in your browser. Click a device in the diagram to open its console and type commands, just like on real equipment (? shows help, Tab finishes a word). Click a cable to inspect it. Tasks tick themselves off as you complete them; questions are answered in the box under each task. Your work is kept if you reload; Reset starts the network over.
Hints
Compare show running-config interface g0/0 on R1 with show interfaces status on SW1.
Solution explanation
R1's Gi0/0 was forced to 100 Mb/s full duplex, which switches autonegotiation off. The switch port could still sense 100 Mb/s but got no duplex answer, so it fell back to half duplex (a-half). With one side half and the other full, the half side sees late collisions and the full side gets CRC errors and runts. Putting R1 back to speed auto and duplex auto let both ends negotiate full duplex.
Show solution
[SW1]
enable
show interfaces status | include Fa0/24
[R1]
enable
ping 192.168.1.10 repeat 20
[SW1]
show interfaces fa0/24 | include collision
[R1]
configure terminal
interface g0/0
speed auto
duplex auto
end
copy running-config startup-config
<enter>
ping 192.168.1.10 repeat 20