DNS Client Issues
- DNS issue is indicated when a host can ping a server by its IP address, but not its name
- when a host receives a client request to access a name and it does not have the IP mapping cached,
- it asks a name server configured as a resolver to perform the lookup and return the IP address
- most hosts are configured with primary and secondary name server resolvers for redundancy
- server addresses are entered as IPv4 and IPv6 addresses
- in most cases these are autoconfigured with DHCP
- when a host receives a client request to access a name and it does not have the IP mapping cached,
- if a single client is unable to resolve host names, the issue is likely with the client’s configuration
- view the name servers configured as resolvers:
- in Windows, using
ipconfig /all - in Linux, DNS server addresses are recorded in
/etc/resolv.conf- typically a package such as NetworkManager or systemd-networkd would add the entries
- entries added directly will be overwritten at reboot
- in Windows, using
- view the name servers configured as resolvers:
- if a host cannot resolve names,
- check:
- that the correct name server address have been configured
- and that you can ping them
- if there are errors:
- correct them (if the interface is statically configured)
- or investigate the automatic addressing server
- if there are connectivity errors:
- check the network path between the host and its name server
- check:
- if multiple clients are affected, the issue is likely the server service (or way a subnet accesses the server service)
- check that the server configured as a DNS resolver is online and available (can ping)
- DHCP might be configuring DNS server settings incorrectly
- check server options or scope options configuration on the DHCP server
Info
- a host can use multiple methods for name resolution via DNS
- especially on Windows workgroup networks
- link local multicast name resolution (LLMNR)
- multicast DNS (mDNS)
- both are modified forms of DNS that allow clients to perform name resolution on a local link without needing a server
Info
- hosts have a system DNS configuration
- apps, such as browsers, might use separately configured name servers