Support plan

• is this issue currently blocking your project? (yes/no): no
• is this issue affecting a production system? (yes/no): no

Context

• node version: v12.13.1
• module version with issue: v17.4.2
• last module version without issue: N/A
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): standalone
• any other relevant information: N/A

What are you trying to achieve or the steps to reproduce?

Joi.string().hostname() handles CIDR notation as a valid hostname:

const Joi = require('joi');

const hostnameSchema = Joi.string().hostname();

console.log(hostnameSchema.validate('10.10.10.10/24'));

What was the result you got?

No validation error

What result did you expect?

A validation error with a "value" must be a valid hostname message field