Constant
Maximum Transmission Unit (MTU)
Definition: Size of the data that can be sent through the network without being fragmented.
MTU Size Configuration
- MTU sizes are usually configured once. Based on the network infrastructure, it does not change often.
Challenges with MTU Discovery
- Automated methods are inaccurate.
- Especially when ICMP Protocol is filtered.
Significant Concern for Tunneled Traffic (VPN)
The tunnel might be smaller than your local Ethernet segment.
What If You Send Data Too Large with DF Set?
DF = Don’t Fragment - Routers will respond back and tell you to fragment the data. - You need to receive ICMP Protocol message (data is too large to send).
Check Whether Data Is Too Large
- Troubleshoot using ping Command
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Ping with DF forces a particular size of data:
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1500 bytes - 8 bytes ICMP Protocol header - 20 bytes IP = 1472
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Windows:
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macOS and Linux:
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