Examkin

Soru

Zorluk: ZorTroubleshooting DNS and Name Resolution Services

A network administrator is troubleshooting an issue where a client workstation fails to connect to an internal database server named `db01.prod.lan`. The technician executes two commands on the workstation and observes the following output:

C:\Users\Admin> ipconfig /displaydns

Record Name . . . . . : db01.prod.lan
Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 10.20.4.150

C:\Users\Admin> nslookup db01.prod.lan 192.168.1.10
Server: dns01.corp.lan
Address: 192.168.1.10

Name: db01.prod.lan
Address: 10.20.4.200

Which TWO of the following statements correctly identify the cause of the connection failure and the required step to resolve it?

  1. The client system is attempting to connect using a stale IP address stored in its local DNS resolver cache.Cevap
  2. Running `ipconfig /flushdns` on the workstation will clear the outdated entry and allow applications to obtain the updated IP address from the DNS server.Cevap
  3. C
    The `nslookup` command returned an invalid answer because it queried the local HOSTS file rather than the specified DNS server.
  4. D
    An AAAA record must be created on the primary DNS server to synchronize the IPv4 address mapping across subnets.

Cevap

The workstation is attempting to connect to the server using a stale IP address stored in its local DNS resolver cache. Running `ipconfig /flushdns` on the client clears this cached entry so the system queries the authoritative DNS server for the correct address.
The output demonstrates that the client's local DNS resolver cache holds an outdated A record (`10.20.4.150`), which the OS uses when applications initiate network traffic. Because `nslookup` bypasses local client caching and queries the DNS server directly, it returns the current IP address (`10.20.4.200`). Flushing the local resolver cache with `ipconfig /flushdns` purges the stale entry and restores proper connectivity.

Adım Adım Çözüm

1
Analyze the output of `ipconfig /displaydns`.
The local DNS cache holds an entry for `db01.prod.lan` pointing to `10.20.4.150` with a TTL of 86,400 seconds.
When standard applications request name resolution, the OS checks its local resolver cache before sending a query across the network.
2
Analyze the output of `nslookup db01.prod.lan 192.168.1.10`.
The DNS server `192.168.1.10` resolves `db01.prod.lan` to `10.20.4.200`.
The `nslookup` utility bypasses local OS cache mechanisms and queries the specified DNS server directly, revealing that the DNS server has the updated record.
3
Determine the necessary remediation.
Clearing the cache via `ipconfig /flushdns` removes the stale entry, forcing subsequent application lookup requests to query the DNS server.
Removing the cached record ensures the client receives the active IP address (`10.20.4.200`).

Anahtar Kavram

Operating System DNS Resolver Cache vs. Direct Command-Line DNS Queries
Bu soruyu puanla

Konular

Troubleshooting DNS and Name Resolution Services

Bu konudan daha fazla soru