DNS Tool

SRV Lookup

Lookup SRV records to validate target, port, priority, and weight for service discovery. Run fast checks, interpret results, and use related tools for…

Record Type

SRV

Focused record verification for targeted DNS troubleshooting.

Best Use

Migration + incident checks

Validate live DNS answers during change windows.

Operational Context

Use this page to validate live resolver output during DNS cutovers, outage triage, and post-change verification windows.

SRV Lookup — Start Here

Waiting for input

Enter a domain and run check

How to Use

Use SRV Lookup in 4 Steps

Enter domain

Input the target domain in clean hostname format (no path or query string).

Run SRV Lookup

Execute SRV Lookup to pull live resolver output for this record scope.

Compare expected vs live

Match returned values with your intended DNS configuration at the source.

Cross-check related tools

Validate adjacent DNS layers to isolate cache vs source problems.

What is SRV Lookup?

SRV (Service) records enable service discovery by advertising which hosts serve a specific protocol and service at a domain. Each SRV record includes priority, weight, port, and target hostname. They're used for SIP/VoIP, XMPP/chat, Microsoft Active Directory, CalDAV, and Kubernetes external service DNS.

The SRV record name follows the pattern `_service._proto.domain` — for example, `_sip._tcp.example.com` or `_xmpp-client._tcp.example.com`. Multiple SRV records for the same service enable load balancing via weight (proportional traffic) and failover via priority (lower = preferred). RFC 2782 requires that SRV targets must be hostnames, not IP addresses.

Best Use

Diagnosing failed SIP/VoIP autodiscovery, validating Microsoft Active Directory DNS, and troubleshooting CalDAV/CardDAV client configuration.

Common Mistake

Using an IP address as the SRV record target. RFC 2782 requires the target field to be a hostname that resolves to an A or AAAA record — bare IPs are invalid and will break strict RFC-compliant clients.

Validation Path

Verify priority/weight/port/target fields, then confirm the target hostname resolves to a valid A or AAAA record with a separate DNS lookup.

Quick Interpretation Table

Use this reference to diagnose common outcomes when running SRV Lookup.

Observed Result	Likely Cause	Next Step
No SRV record found	Service autodiscovery unavailable for this protocol	Publish SRV at _service._proto.domain with correct priority/weight/port/target
SRV target is an IP address	Invalid per RFC 2782 — clients may reject it	Replace the target with a valid hostname that resolves to an A/AAAA record
Multiple SRVs with identical priority	Weight-based load balancing is active	Verify weight ratios match intended load distribution (higher weight = more traffic)

CLI Examples

Run these commands directly from a terminal to verify SRV records without relying on a browser-based tool.

dig SRV _sip._tcp.example.com

Query SRV records for SIP over TCP

dig SRV _xmpp-server._tcp.example.com

Query SRV records for XMPP server federation

nslookup -type=SRV _caldavs._tcp.example.com

Query CalDAV-over-TLS SRV records using nslookup

dig SRV _sipfederationtls._tcp.example.com

Query Microsoft Teams/Lync federation SRV record

Troubleshooting Workflow

Run this record check first for a scoped signal on the target hostname.
Validate nameserver authority and SOA context if results are unexpected.
Use propagation checks when different regions return different values.
Re-run after applying fixes and compare values against your expected configuration.

Frequently Asked Questions

What is an SRV record?

An SRV (Service) record encodes service-location information in DNS. The record name uses the pattern `_service._proto.domain` (e.g., `_sip._tcp.example.com`). Each SRV record specifies priority (failover order), weight (load distribution), port (service port), and target hostname for a service endpoint.

What do priority and weight mean in SRV records?

Priority controls failover — clients always try the lowest priority value first and fall back to higher values if unavailable. Weight controls proportional load distribution among records of equal priority — a weight of 90 versus 10 means 90% of traffic goes to the first server. A weight of 0 removes it from load balancing.

What services use SRV records?

Common SRV users: SIP/VoIP (`_sip._tcp`, `_sip._udp`), XMPP/Jabber (`_xmpp-client._tcp`, `_xmpp-server._tcp`), Microsoft Teams/Lync (`_sipfederationtls._tcp`, `_sip._tls`), CalDAV/CardDAV (`_caldavs._tcp`, `_carddavs._tcp`), and Microsoft Active Directory (multiple `_ldap._tcp`, `_kerberos._tcp` records per site).

Why does my SRV lookup return no results?

Possible causes: (1) the `_service._proto.domain` name is wrong — verify the exact service and protocol strings required by your application, (2) the record doesn't exist yet at your DNS provider, (3) a DNS firewall or resolver is filtering SRV responses. Query the authoritative nameserver directly (`dig SRV ... @ns1.example.com`) to bypass cache issues.

Can SRV records point to a CNAME target?

RFC 2782 strongly discourages using a CNAME as an SRV target. The target must be a hostname with A/AAAA records. Using a CNAME as the SRV target technically works in some resolvers but can break strict RFC-compliant clients like SIP phones and Microsoft Lync/Teams servers.