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# secondary
## Name
*secondary* - enables serving a zone retrieved from a primary server.
## Description
With *secondary* you can transfer (via AXFR) a zone from another server. The retrieved zone is
*not committed* to disk (a violation of the RFC). This means restarting CoreDNS will cause it to
retrieve all secondary zones.
~~~
secondary [ZONES...]
~~~
* **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
are used. Note that without a remote address to *get* the zone from, the above is not that useful.
A working syntax would be:
~~~
secondary [zones...] {
transfer from ADDRESS
transfer to ADDRESS
upstream
}
~~~
* `transfer from` specifies from which address to fetch the zone. It can be specified multiple times;
if one does not work, another will be tried.
* `transfer to` can be enabled to allow this secondary zone to be transferred again.
* `upstream` resolve external names found (think CNAMEs) pointing to external names. This is only
really useful when CoreDNS is configured as a proxy; for normal authoritative serving you don't
need *or* want to use this. CoreDNS will resolve CNAMEs against itself.
When a zone is due to be refreshed (Refresh timer fires) a random jitter of 5 seconds is
applied, before fetching. In the case of retry this will be 2 seconds. If there are any errors
during the transfer the transfer fails; this will be logged.
## Examples
Transfer `example.org` from 10.0.1.1, and if that fails try 10.1.2.1.
~~~ corefile
example.org {
secondary {
transfer from 10.0.1.1
transfer from 10.1.2.1
}
}
~~~
Or re-export the retrieved zone to other secondaries.
~~~ corefile
. {
secondary example.net {
transfer from 10.1.2.1
transfer to *
}
}
~~~
## Bugs
Only AXFR is supported and the retrieved zone is not committed to disk.
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