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Troubleshooting Name Resolution  

 
Sohaib
(@sohaib-ops)
Member Admin

tracert or traceroute:

The tracert or traceroute commands are used to show details about the path that a packet takes from the computer to whatever destination you specify.

nslookup:

A command-line tool used (in Windows and other operating systems) to query the Domain Name System (DNS) to obtain the domain name, the IP address mapping, or for any other specific DNS record.

dig:

Domain Information Groper (dig) is a Unix-like network administration command-line tool used to determine what a particular DNS server thinks the given host’s IP address should be.

Quote
Posted : 24/01/2020 6:51 pm
Sohaib
(@sohaib-ops)
Member Admin

Common name resolution problems include the following:

• The DNS server could be down or otherwise unreachable.
• There may be a routing problem between the sending host and the DNS server.
• The sending host could be configured with the wrong IP address for the DNS server.

Name resolution problems typically have the following symptoms:

• You can ping a destination host using its IP address, but not its host name.
• Applications that use hostnames fail. This could include:
◦ Entering a URL into a browser.
◦ Pinging the host using the hostname.
◦ Searching for the host by its name.

To troubleshoot DNS name resolution, use the following tools:
• ping
• tracert (Windows) or traceroute (Linux)
• nslookup
• dig (Linux)
• host (Linux)

ReplyQuote
Posted : 24/01/2020 6:53 pm
Sohaib
(@sohaib-ops)
Member Admin

Troubleshoot DNS Name Resolution With Commands

ping:

Contacts the DNS server to see if it responds. Be aware that the firewall protecting the DNS server may be configured to drop ICMP packets in order to prevent DoS attacks; if the server doesn't respond, it is not necessarily down.

Example: ping 8.8.4.4

tracert or traceroute:

Tests the route between your workstation and the DNS server.

Example: tracert 8.8.4.4

nslookup [host]:

Queries the IP address of a host.

Example: nslookup www.mit.edu

nslookup:

Starts nslookup in interactive mode. The default interactive mode query is for A records, but you can use the set type= command to change the query type.

Example: nslookup set type=ns

dig host name && host host name:

Queries a host. The default query is for A records. You can change the default search by appending one of the record types below to the end of the command:
• a—address records
• any—any type of record
• mx—mail exchange records
• ns—name server records
• soa—sort of authority records
• hinfo—host info records
• axfr—all records in the zone
• txt—text records

Example:dig www.vulture.com ns
host www.vulture.com -t ns

dig @IP address or host name domain:

Queries the root server at the IP address or host name for the domain's A records. You can change the default query type by appending a different record type to the end of the command.

Example: dig @192.168.1.1 vulture.com ns

dig -x IP address && host IP address:

Finds the host name for the queried IP address.

Example: dig -x 62.34.4.72
host 62.34.4.72

**Note**
Local computers have a cache of recently resolved DNS names. The cache holds the DNS name and its IP address. When you use a DNS name, the computer first checks its cache. If the name is in the cache, the corresponding IP address is used. This can cause problems if a host's IP address has changed. Old values in the cache might continue to be used temporarily, making communication via the DNS name impossible. To correct this problem on a Windows computer, run ipconfig /flushdns to delete the local DNS name cache.

ReplyQuote
Posted : 24/01/2020 6:59 pm