transfer speed of a cabled link could be reduced by mismatched duplex settings on the network adapter and switch port
With Gigabit Ethernet, both should be set to autonegotiate
Check the configuration of the network adapter driver on the client OS and the setting for the switch port via the switch’s management software
If there is no configuration issue, slow network speeds can be caused by a variety of other problems and are difficult to diagnose
Structured Process to Investigate Possible Causes
If a user reports slow speed,
establish exactly what network activity they are performing
Establish that there is a link speed problem by checking the nominal link speed and using a utility to measure transfer rate independent of specific apps or network services
If you can isolate the speed issue to a single cable segment,
the cabling could be affected by interference
External interference is typically caused by nearby power lines, fluorescent lighting, motors, and generators
Poorly installed cabling and connector termination can also cause a type of interference called crosstalk
Check the ends of cables for excessive untwisting of the wire pairs or improper termination
If you have access to a network tap, the analyzer software is likely to report high numbers of damaged frames
view error rates from the switch interface configuration utility
If the cabling is not the issue,
could be a problem with the network adapter driver
Install an update if available
If the latest driver is installed, check whether the issue affects other hosts using the same NIC and driver version
Consider the possibility that the computer could be infected with malware or have faulty software installed
Consider removing the host from the network for scanning
If you can install a different host to the same network port and that solves the issue, identify what is different about the original host
Establish the scope of the problem:
are network speeds an issue for
a single user
for all users connected to the same switch
or for all users connecting to the Internet
may be congestion at a switch or router or some other network-wide problem
this might be caused by a fault or by user behavior, such as transferring a very large amount of data over the network