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I have encountered one unique problem with a few networked computers in my lab. whereas most computers can access the internet, some do not- though the cables are fitted!!

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This thread describes a common lab symptom: several wired PCs appear physically connected but cannot reach the internet. Replies from , , and point toward both host- and infrastructure-side causes. The short checklist below fills gaps in the replies and gives a repeatable, evidence-first workflow.

First, isolate whether the fault follows the machine or the wall port. Swap a known-good laptop into the suspect jack, then put the suspect machine onto a known-good jack. If the problem moves with the machine, focus on OS, drivers, firewall/proxy, or a faulty NIC. If the problem stays with the jack, focus on patching, the switch port, VLAN or upstream device. A temporary USB-to-Ethernet adapter or a Linux live-USB can quickly prove whether the installed OS is involved.

On the switch/router side, look for infrastructure symptoms that user posts did not expand on: port error-disable states, port-security MAC lockouts, VLAN misassignment, frequent link flaps, CRC/FCS counters and speed/duplex mismatches. Inspect the switch MAC table to confirm the device is learned on the expected port. Check DHCP server logs for exhausted scopes or rogue DHCP servers. Avoid changing switch config on production hardware without a maintenance window.

Capture the right evidence before changing anything. Useful quick checks and captures:

# reachability and path
ping -c 4 8.8.8.8
traceroute 8.8.8.8

# DNS and ARP
nslookup example.com 8.8.8.8
arp -a

# Linux link diagnostics and DHCP capture
ethtool eth0
sudo tcpdump -i eth0 -n port 67 or port 68

Cautions: label and document patch-panel moves, replace suspect patch cords, and avoid ad-hoc switch resets. If a capture shows no DHCP traffic from the client, the fault is physical or switch-side; if DHCP succeeds but no internet follows, examine router/NAT and ACLs.

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All 6 Replies

Member Avatar for barryt

wow u really have to give more info??
are all on the same network with the same ip range ?
are you sure it is network cables and not power cables?
what is the results for the "ipconfig /all" command if it is windows machines?
and and and...
b

Member Avatar for Member #579261

check the default gateway, it should be the same on all the PC's if they're in the same Network.

Member Avatar for mambacroco

check the Ip address of the computers

Member Avatar for mambacroco

first is the local network active on computer?
check if you can be able to access them?
there must be a problem with the network cable

Member Avatar for deadmantz

I have encountered one unique problem with a few networked computers in my lab. whereas most computers can access the internet, some do not- though the cables are fitted!!

Hi !

The thing that should be checked is the ethnet (NIC) adoptor and you should make sure that all the cables connected to those computers are in a good condiotion, because some times when the cable have been used for a long time they tend to loose strenth and course signal fail from the main server.

Deadmantz.

Member Avatar for house of mumbi

I think your take on this "job" could be true, and I say, asante for your help and for all those who managed to give their sols...

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