Maximum Transmission Unit (MTU)

The MTU (or to be exact, 'protocol MTU') of a link (logical IP subnet) describes the maximum size of an IP packet that can be transferred over the link without fragmentation. Common MTUs include

  • 1500 bytes (Ethernet, 802.11 WLAN)
  • 4470 bytes (FDDI, common default for POS and serial links)
  • 9000 bytes (Internet2 and GÉANT convention, limit of some Gigabit Ethernet adapters)
  • 9180 bytes (ATM, SMDS)

For entire network paths, see PathMTU. For specific information on configuring large (Jumbo) MTUs, see JumboMTU.

The term 'media MTU' is used to refer to the maximum sized Layer 2 PDU that a given interface can support. Media MTU bust equal to or greater the sum of protocol MTU and the Layer 2 header.


-- SimonLeinen - 27 Oct 2004
-- TobyRodwell - 24 Jan 2005
-- MarcoMarletta - 20 Jan 2006

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Topic revision: r9 - 2007-08-28 - TobyRodwell
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