Host Header is a request HTTP header that specifies the domain name of the server on which the server is listening. Usually, the Host header is the same as your Origin Source.
To manage the option go to Advanced Settings and find the Change Host Header option.
You can set up this option in two ways:
Custom Host header - this variant is chosen by default when you create a CDN resource, the Custom Host header value automatically sets as equal to an Origin source. You can write a custom value.
Forward Host header - when CDN requests content from an origin server we will forward the Host header used in the request made to a CDN.
Check if the header is right
Use the following command in the terminal:
curl -I -k -H "Host:cdn.site.com" https://126.96.36.199
cdn.site.com — the host header that you specified in the Host Header option
https://site.ru — your Origin Source or origin IP
If you get the 400 Bad Request or 403 Forbidden response, your server cannot process the header you specified. You need to specify another header.
Origin group and Host header
When you change the Origin group in the CDN Resource settings the Host header value gets changed automatically to the first origin on the new Origin group list.