fallback

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fallback:github.com/coredns/fallback

fallback - allow redirecting queries to an alternate set of upstreams based on RCODE

Description

The fallback plugin allows an alternate set of upstreams be specified which will be used if the plugin chain returns specific error messages. The fallback plugin utilizes the proxy plugin (https://coredns.io/plugins/proxy) to query the specified upstreams.

As the name suggests, the purpose of the fallback is to allow a fallback when, for example, the desired upstreams became unavailable.

It is recommended that this comes before proxy and forward in the plugins.cfg file. It must come before any plugins for which it wants to react to their response code.

Syntax

fallback RCODE PROXY_PARAMS

Examples

Fallback to local DNS server

The following specifies that all requests are proxied to 8.8.8.8. If the response is NXDOMAIN, fallback will proxy the request to 192.168.1.1:53, and reply to client accordingly.

. {
	proxy . 8.8.8.8
	fallback NXDOMAIN . 192.168.1.1:53
	log
}

Multiple fallbacks

Multiple fallbacks can be specified, as long as they serve unique error responses.

. {
    proxy . 8.8.8.8
    fallback NXDOMAIN . 192.168.1.1:53
    fallback REFUSED . 192.168.100.1:53
    log
}

Additional proxy parameters

You can specify additional proxy parameters for each of the fallback upstreams.

. {
    proxy . 8.8.8.8
    fallback NXDOMAIN . 192.168.1.1:53 192.168.1.2:53 {
        protocol dns force_tcp
    }
    log
}