# Certbot/Letsencrypt authenticator IP addresses

**URL:** https://community.letsencrypt.org/t/certbot-letsencrypt-authenticator-ip-addresses/42693
**Category:** Issuance Tech
**Created:** [September 21, 2017, 3:27am UTC](https://community.letsencrypt.org/t/certbot-letsencrypt-authenticator-ip-addresses/42693 "2017-09-21T03:27:19Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![schoen](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/schoen/32/79_2.png) [@schoen](https://community.letsencrypt.org/u/schoen)
#### Post date: [September 21, 2017, 4:41am UTC](https://community.letsencrypt.org/t/certbot-letsencrypt-authenticator-ip-addresses/42693/2 "2017-09-21T04:41:46Z")

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Hi @rgould,

You should not use a validation method that requires an inbound connection in this case, because the validation IP addresses may change frequently in order to be deliberately unpredictable. Please see

> [@New validation IP addresses](https://community.letsencrypt.org/t/new-validation-ip-addresses/35987):
>
> A…

> [@Frequently Asked Questions (FAQ)](https://community.letsencrypt.org/t/frequently-asked-questions-faq/26):
>
> P…

The validation method that doesn't require an inbound connection to your server is the DNS-01 method, which requires you to create a specified DNS TXT record in your domain's DNS zone.

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