# BIG-IP methods to Fix the “421 Misdirected Request” Error

**URL:** <https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502>\
**Category:** Technical Forums\
**Tags:** sni, apache\
**Created:** [September 4, 2025, 10:56am UTC](https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502 "2025-09-04T10:56:03Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Pete\_A](https://avatars.discourse-cdn.com/v4/letter/p/ed655f/32.png) [@Pete\_A](https://community.f5.com/u/Pete_A)\
**Post date:** [September 4, 2025, 10:56am UTC](https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502/1 "2025-09-04T10:56:03Z")

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For those of us that are using the BIG-IP as a reverse proxy to front our internal websites to the world, the recent update to Apache has slapped a big “misdirected request” error across our shop windows.

The fix is that apache is looking for the SNI headers (that’s different from the HTTP headers I originally was working with).&nbsp; The solution to this, for us anyway, was published ages ago in the thread: [Serverside SNI injection iRule | DevCentral](https://community.f5.com/topic/286745)

Drop that in your iRule and the world starts working again.

Peace, Love and chocolate biscuits all round.

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**Author:** ![LiefZimmerman](https://d1p9zq3aats0t8.cloudfront.net/user_avatar/community.f5.com/liefzimmerman/32/3355_2.png) [@LiefZimmerman](https://community.f5.com/u/LiefZimmerman)\
**Post date:** [September 18, 2025, 5:52pm UTC](https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502/2 "2025-09-18T17:52:19Z")

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Thanks for dropping this use-case / solution pairing @Pete_A .  
Happy to hear that&nbsp; @Kai_Wilke 's codeshare still has legs.

(I’ll further drop the link you provided in a comment associated with you and **mark as solution** - if you disagree for some reason let me know.)

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**Author:** ![Pete\_A](https://avatars.discourse-cdn.com/v4/letter/p/ed655f/32.png) [@Pete\_A](https://community.f5.com/u/Pete_A)\
**Post date:** [September 18, 2025, 5:54pm UTC](https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502/3 "2025-09-18T17:54:48Z")

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[Serverside SNI injection iRule | DevCentral](https://community.f5.com/topic/286745) - solved the “421 Misdirected Request” error when using BIG-IP as a reverse proxy…

(Admin note: adding this explicitly as a comment for @Pete_A and marking as Solution - to increase likelihood of finding.)

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**Author:** ![ASCapi](https://d1p9zq3aats0t8.cloudfront.net/user_avatar/community.f5.com/ascapi/32/23319_2.png) [@ASCapi](https://community.f5.com/u/ASCapi)\
**Post date:** [October 6, 2025, 8:25am UTC](https://community.f5.com/t/big-ip-methods-to-fix-the-421-misdirected-request-error/76502/4 "2025-10-06T08:25:02Z")

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Hi,

It’s usefull Thank you for you sharing.  
I use it to fix http status 421 after Apache2 update.

Well done !