# Introducing the J2sw MTU and Encapsulation Calculator

DevFeed: [Introducing the J2sw MTU and Encapsulation Calculator](<https://devfeed.tech/articles/introducing-the-j2sw-mtu-and-encapsulation-calculator-40186.md>)

Original publisher: [Read original article](<https://blog.j2sw.com/resources/mtu-encapsulation-calculator/>)

Author: j2sw

Published: 2026-07-28T16:37:53Z

Content type: tutorial

Language: en

Sources: [Justin Wilson (j2sw)](<https://devfeed.tech/sources/justin-wilson-j2sw.md>)

Topics: [Network](<https://devfeed.tech/topics/network.md>), [Tool](<https://devfeed.tech/topics/tool.md>), [Ethernet](<https://devfeed.tech/topics/ethernet.md>), [VXLAN](<https://devfeed.tech/topics/vxlan.md>)

Tags: [calculator](<https://devfeed.tech/tags/calculator.md>), [cisco](<https://devfeed.tech/tags/cisco.md>), [ethernet](<https://devfeed.tech/tags/ethernet.md>), [fragmentation](<https://devfeed.tech/tags/fragmentation.md>), [gre](<https://devfeed.tech/tags/gre.md>), [headers](<https://devfeed.tech/tags/headers.md>), [ipsec](<https://devfeed.tech/tags/ipsec.md>), [ipv4](<https://devfeed.tech/tags/ipv4.md>), [ipv6](<https://devfeed.tech/tags/ipv6.md>), [juniper](<https://devfeed.tech/tags/juniper.md>), [mikrotik](<https://devfeed.tech/tags/mikrotik.md>), [mpls](<https://devfeed.tech/tags/mpls.md>), [mtu](<https://devfeed.tech/tags/mtu.md>), [network-engineering-resources](<https://devfeed.tech/tags/network-engineering-resources.md>), [network-tools](<https://devfeed.tech/tags/network-tools.md>), [network-troubleshooting](<https://devfeed.tech/tags/network-troubleshooting.md>), [overhead](<https://devfeed.tech/tags/overhead.md>), [payload](<https://devfeed.tech/tags/payload.md>), [pppoe](<https://devfeed.tech/tags/pppoe.md>), [vlan](<https://devfeed.tech/tags/vlan.md>), [vxlan](<https://devfeed.tech/tags/vxlan.md>)

## AI overview

The article introduces the J2SW MTU and Encapsulation Calculator, which estimates inner IP MTU and required underlay MTU for combinations of PPPoE, GRE, VLAN, MPLS, VXLAN, and other encapsulations. It explains how Layer 2 tags affect Ethernet frame size separately from IP MTU and describes overhead calculations, including cases where fragmentation can be avoided.

## Source excerpt

Ever wondered what the effects of different combinations of PPPoE, GRE, and others have on the MTU of a packet? I am excited to announce the first of many J2 Network tools: the J2SW MTU and Encapsulation Calculator. You select the service MTU and the encapsulation used on the path. The calculator then works out ... Read more The post Introducing the J2sw MTU and Encapsulation Calculator appeared first on Justin Wilson (j2sw).