delv

delv is a command-line utility used for DNS troubleshooting and debugging. It is part of the BIND (Berkeley Internet Name Domain) DNS software suite and provides a way to perform DNS lookups and validate DNS responses.

Overview of delv

Purpose

The main purpose of delv is to perform DNS queries and validate DNSSEC-signed zones. It allows administrators and users to manually inspect DNS records, troubleshoot DNS resolution issues, and verify the integrity of DNS responses using DNSSEC.

Basic Usage

The general syntax for delv is:

delv [options] [@server] <name> [<type> [<class>]]

• [options]: Various options to control the behavior of delv.

• [@server]: Optional parameter specifying the DNS server to query.

• <name>: The domain name to query.

• <type>: Optional DNS record type to query (default is A for IPv4 address).

• <class>: Optional DNS class (default is IN for Internet).

Example Usages

1. Basic Query:

   To query an A record for a domain (e.g., example.com) using a specific DNS server (8.8.8.8):

   delv @8.8.8.8 example.com A

2. Query with DNSSEC Validation:

   To perform a DNSSEC-enabled query for an A record for a domain (e.g., example.com):

   delv -D example.com A

   This command validates DNSSEC signatures in the responses received.

3. Query for Other Record Types:

   To query for other types of DNS records, such as MX (Mail Exchange) records:

   delv example.com MX

Features and Options

• DNSSEC Validation (-D): Enables DNSSEC validation for the queried records.

• Verbose Output (-v): Provides more detailed information about the DNS query and response.

• Specifying DNS Server (@server): Allows querying a specific DNS server instead of using the system's default resolver.

• Querying Specific Record Types: Supports querying for various DNS record types like A, AAAA, MX, TXT, NS, etc.

• Debugging and Troubleshooting: Useful for debugging DNS issues, checking DNS configuration, and verifying DNS responses.

Integration with DNSSEC

delv is particularly useful for validating DNSSEC-signed zones. By enabling DNSSEC validation (-D option), delv checks the authenticity and integrity of DNS responses using digital signatures.

Conclusion

delv is a versatile tool for DNS troubleshooting and debugging, providing administrators and users with the ability to manually query DNS servers, inspect DNS records, and validate DNSSEC-signed zones. Understanding its usage and options is valuable for diagnosing and resolving DNS-related issues effectively.