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Overview

Reverse DNS maps IP addresses back to hostnames using PTR records. This is distinct from forward DNS (hostname to IP) — PTR records live in special reverse zones (in-addr.arpa. for IPv4 and ip6.arpa. for IPv6). Reverse DNS is required by mail servers for spam reputation checks and improves audit log readability.
Prerequisites
  • An active Xloud account with appropriate permissions
  • Access to the Xloud Dashboard (https://connect.<your-domain>) or CLI configured with credentials
  • API credentials sourced (source admin-openrc.sh)
The reverse zone for your IP range (e.g., 1.168.192.in-addr.arpa.) is managed automatically by the DNS service for addresses within your allocation. You do not need to create or manage these reverse zones manually.

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How Reverse DNS Works

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Configure a PTR Record

1

Navigate to Reverse DNS

Navigate to Project → DNS → Reverse DNS. Select the Floating IPs or Fixed IPs tab depending on the IP type you want to configure.
2

Set the PTR record

Click Set next to the IP address and enter the fully qualified domain name including the trailing dot (e.g., mail.example.com.).The PTR zone (e.g., 1.168.192.in-addr.arpa.) is managed automatically by the DNS service — you do not need to create it manually.
IPv6 PTR records use the ip6.arpa. reverse zone. The DNS service handles zone delegation automatically for addresses in your allocation.
3

Verify the PTR record

After setting, verify the PTR record resolves correctly:
Test reverse DNS
dig -x 192.168.1.10 @<nameserver-ip>
The answer section shows mail.example.com. for the queried IP.

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Manage PTR Records

openstack ptr record show <region>:<floating-ip-id>

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IPv6 Reverse DNS

IPv6 PTR records follow the same process as IPv4, but the reverse zone uses the ip6.arpa. domain. The DNS service handles the zone delegation automatically.
Set PTR record for an IPv6 floating IP
openstack ptr record set \
  <region>:<ipv6-floating-ip-id> \
  ipv6-host.example.com.
IPv6 reverse zones are automatically delegated for your allocated prefix. No manual zone creation is required.

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Next Steps

Manage Records

Add forward DNS records to complement your PTR configuration

Record Types Reference

Reference for all supported DNS record types

Troubleshooting

Resolve PTR record failures and zone delegation issues

DNS Admin Guide

Administer reverse zone pools and nameserver delegation