# Setting a MTU value

**URL:** <https://mediasoup.discourse.group/t/setting-a-mtu-value/6379>\
**Category:** mediasoup libraries\
**Created:** [December 5, 2024, 7:19pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379 "2024-12-05T19:19:47Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![thenowhere](https://avatars.discourse-cdn.com/v4/letter/t/34f0e0/32.png) [@thenowhere](https://mediasoup.discourse.group/u/thenowhere)\
**Post date:** [December 5, 2024, 7:19pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/1 "2024-12-05T19:19:47Z")

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I’ve been looking through the docs but can’t find information on how we can set a MTU value. Does Mediasoup support this as a config option?

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**Author:** ![ibc](https://yyz2.discourse-cdn.com/free1/user_avatar/mediasoup.discourse.group/ibc/32/1540_2.png) [@ibc](https://mediasoup.discourse.group/u/ibc)\
**Post date:** [December 5, 2024, 9:14pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/2 "2024-12-05T21:14:21Z")

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No. There is a const MTU\_SIZE=1200 AFAIR which is static and the same value that libwebrtc uses.

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**Author:** ![thenowhere](https://avatars.discourse-cdn.com/v4/letter/t/34f0e0/32.png) [@thenowhere](https://mediasoup.discourse.group/u/thenowhere)\
**Post date:** [December 6, 2024, 6:28pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/3 "2024-12-06T18:28:08Z")

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ok, do you have any advice on forcing the MTU? I have packets being sent close to 1500 which is past the limit for a number of clients.

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**Author:** ![ibc](https://yyz2.discourse-cdn.com/free1/user_avatar/mediasoup.discourse.group/ibc/32/1540_2.png) [@ibc](https://mediasoup.discourse.group/u/ibc)\
**Post date:** [December 6, 2024, 6:37pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/4 "2024-12-06T18:37:18Z")

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mediasoup never sends a packet bigger than 1200 bytes and there is something called IP fragmentation that works transparently at IP level for decades (unless clients or service providers block ICMP “for WRONG security reasons” so they kill the MTU discovery mechanism which is based on ICMP.

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<div class="post-metadata">

**Author:** ![thenowhere](https://avatars.discourse-cdn.com/v4/letter/t/34f0e0/32.png) [@thenowhere](https://mediasoup.discourse.group/u/thenowhere)\
**Post date:** [December 6, 2024, 6:43pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/5 "2024-12-06T18:43:09Z")

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Yes, I’m pretty sure this is what’s occurring in my situation. I’m just having trouble finding a work-around.

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<div class="post-metadata">

**Author:** ![ibc](https://yyz2.discourse-cdn.com/free1/user_avatar/mediasoup.discourse.group/ibc/32/1540_2.png) [@ibc](https://mediasoup.discourse.group/u/ibc)\
**Post date:** [December 6, 2024, 7:14pm UTC](https://mediasoup.discourse.group/t/setting-a-mtu-value/6379/6 "2024-12-06T19:14:13Z")

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Try sending pings (which is ICMP as well) to client’s public IP from your backend to see if it’s blocked.

BTW there is nothing else mediasoup can do here. Clients send packets of up to 1200bytes and mediasoup cannot make them smaller before relaying them to those other problematic clients