---
title: "Why is my secondary server trying sometimes to use a different source "
slug: "aa-00904"
description: "There are several configuration options in named.conf that control which IPv4 and/or IPv6 source addresses are used for the SOA refresh queries and for the zone transfers themselves. See the Administrator Reference Manual for more details."
tags: ["source address"]
updated: 2019-01-16T21:40:34Z
published: 2019-01-16T21:40:34Z
canonical: "kb.isc.org/aa-00904"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.isc.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Why is my secondary server trying sometimes to use a different source IP address for zone transfers?

There are several configuration options in **named.conf** that control which IPv4 and/or IPv6 source addresses are used for the SOA refresh queries and for the zone transfers themselves. See the [Administrator Reference Manual](https://kb.isc.org/docs/aa-01031) for more details.

The well-known ones are these:

**transfer-source** - determines which local IPv4 address will be used as the source for both SOA refresh queries and zone transfer requests that need to be made to servers.

**transfer-source-v6** - the same as transfer-source, but used when the destination is an IPv6 address.

Less well-known are:

**alt-transfer-source** - this provides an alternative local IPv4 source address to use if the first one fails.

**alt-transfer-source-v6** - the same as alt-transfer-source, but used when the destination is an IPv6 address.

**use-alt-transfer-source** - defines whether or not named will fall back to using the alternative source addresses when the first attempt at a zone transfer fails.

@(Info)(If you are using views, the configuration option use-alt-transfer-source will default to 'yes')(Administrators using views should ensure that they either configure **use-alt-transfer-source no;** or that they have appropriate settings for **alt-transfer-source** and/or **alt-transfer-source-v6**.)

@(Info)(If undefined, named will itself choose the source IPv4 or IPv6 address(es) to use)(This applies to both **transfer-source** and **alt-transfer-source** (and also to the IPv6 options). **named** will usually select the source address that is "closest" to the remote end. This can lead to unexpected outcomes - therefore it is best to configure all of these options explicitly to avoid surprises!)