Modify DNS on the core switch

To modify DNS on a core switch, configure the ip name-server entries and ensure ip domain-lookup is enabled, then verify resolution and client access.

Steps to Modify DNS

1. Access the Switch
   • Connect via console or SSH.
   • Enter privileged EXEC mode:

     enable

   • Enter global configuration mode:

     configure terminal

2. Enable Hostname Resolution
   • Ensure the switch can resolve hostnames:

     ip domain-lookup

3. Configure DNS Servers
   • Add one or multiple DNS servers using the ip name-server command:

     ip name-server 8.8.8.8 8.8.4.4 You can list multiple servers in a single command or use separate commands; both methods work and the switch will prioritize them in order .

4. Optional: Configure Domain Name
   • If you want the switch to resolve short hostnames without fully qualified domain names:

     ip domain-name example.com

5. Verify Configuration
   • Check the running configuration:

     show running-config

   • Test DNS resolution from the switch:

     ping hostnamenslookup hostname

6. Client Considerations
   • If the core switch acts as a DNS relay for clients, ensure the DHCP pool includes the switch IP as the DNS server:

     ip dhcp pool VLAN10network 192.168.10.0 255.255.255.0dns-server 192.168.10.1

   • Verify clients can resolve external hostnames through the switch .

Best Practices

• Use DNS servers that are reliable and close to your network for faster resolution .
• Avoid overlapping DHCP pools and exclude static IPs to prevent conflicts.
• Test DNS resolution after changes to ensure proper functionality.
• Document the configuration and maintain backups before making changes . By following these steps, your core switch will correctly resolve hostnames and provide DNS information to clients if configured as a relay.