5.10: Troubleshoot Name Resolution
if you don't specify a type record to perform, dig automatically uses
A
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
Domain Information Groper (dig)
dig is only available by default on
Linux
If your DNS server can resolve local hostnames but cannot resolve hostnames that it is not authoritative for, then you know that there is a ___________, most likely, between the ___________________
connectivity problem, DNS server and the root level name server
To perform a reverse lookup of the 10.0.0.3 IP address, use either of the following commands:
dig -x 10.0.0.3 or nslookup 10.0.0.3
Finds the host name for the queried IP address.
dig -x [IP address], host [IP address]
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.
dig @ip address or host name domain
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:
dig [host name], host [host name]
command for deleting local DNS cache
ipconfig /flushdns
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.
nslookup
Use _____ to troubleshoot name resolution problems. (ex. server's IP address you're trying to connect to responds to pings but you can't connect to it)
nslookup
Queries the IP address of a host.
nslookup [host]
try to resolve a DNS name for which your DNS server is authoritative by using
nslookup or dig
______: Starts nslookup in interactive mode. The default interactive mode query is for __ records, but you can use the ________ command to change the query type.
nslookup, A, set type =
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.
ping
a quick way to test DNS host resolution is by
pinging the host's IP address
default port used by DNS servers
port 53
IP addresses of root-level servers on the internet that are preconfigured to send queries to domain names that they are not authoritative for
root hints
if you ping a DNS server and it doesn't respond, it could mean that there is a routing problem, but it could also be that
the DNS has a firewall
used to show details about the path that a packet takes from the computer to whatever destination you specify
tracert and traceroute
Tests the route between your workstation and the DNS server.
tracert or traceroute
