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MTU Path
Maximum network path size scan utility
For Windows 2000, XP, 2008/Vista and Windows 7 platforms

MTU Path is a utility to assist operators in troubleshooting MTU related network configuration problems by finding the largest one-way path MTU (PMTU) to a remote host or router.

The software works by sending a small number of messages toward a host analyzing feedback from host and intermediate routers to determine largest packet size the network path will accept.

MTU Path example 1

MTU Path example 2

Use instructions
MTU Path is a command line application. To use the software follow the download link below and save the application to a folder. From a command prompt switch to the same folder and run mtupath followed by the IP address or DNS name of the destination host to check. Example: 'mtupath www.iea-software.com'.

Over the next few seconds an MTU estimate is displayed on screen and continually refined until the correct path MTU is discovered.

A series of characters are displayed directly to the right of the path MTU estimate as the scan proceeds. This information is of limited utility intended for support and troubleshooting purposes. Please see the table to the right for information on the meaning of the character display.
PLarge ICMP message
pSmall ICMP message
ULarge UDP message
uSmall UDP message
*Request timed out
?Request failed due to host error

Once a scan is completed tables summarizing distribution of scan results thru the range of MSS values tested by the scan (1 - 16384) are displayed for reference.

MSS IN RANGERange of MSS values are assumed to be supported by the network path.
SCAN TIMEOUTThere was a request timeout testing this specific range. Possible causes include intermittent network problem or administrative limits on ICMP messages.
MSS EXCEEDEDRange of MSS values are assumed not to be supported by the network path.
SCAN FAILUREThere was an internal host error for the range of MSS values scanned.
SOFTWARE ERRA software defect has occurred and should be reported.

MTU Path version 1 features:

    Supports IPv4 and IPv6 networks.
    Leverages multiple measurement strategies to account for a variety of network conditions.
    Find IPv4 path MTU thru misconfigured PMTU black hole routers.
    Warning messages alert of inconsistent results or exceptional conditions potentially affecting the path size estimate.
    Partial path estimate possible if destination host offline.
    Available at no charge for Windows 2000, XP, 2008/Vista and Windows 7 platforms.

Downloading instructions:

Choose your platform to begin downloading MTU Path.