Troubleshooting

DNS Resolver

Operating Notes

Configuring another IP address for a priority that has already been assigned to an IP address is not allowed. To replace one IP address at a given priority level with another address having the same priority, you must first use the no form of the command to remove the unwanted address. Also, only one instance of a given server address is allowed in the server list. Attempting to enter a duplicate of an existing entry at a different priority level is not allowed. To change the priority of an existing server address, use the no form of the command to remove the entry, then re-enter the address with the new priority.

To change the position of an address already configured with priority x, you must first use no ip dns server-address priority x < ip-addr> to remove the address from the configuration, then use ip dns server-address priority < ip-addr> to reconfigure the address with the new priority. Also, if the priority to which you want to move an address is already used in the configuration for another address, you must first use the no form of the command to remove the current address from the target priority.

The DNS server(s) and domain configured on the switch must be accessible to the switch, but it is not necessary for any intermediate devices between the switch and the DNS server to be configured to support DNS operation.

When multiple DNS servers are configured on the switch, they can reside in the same domain or different domains.

A DNS configuration must include the IP address for a DNS server that is able to resolve host names for the desired domain. If a DNS server has limited knowledge of other domains, then its ability to resolve DNS-compatible command requests is also limited.

If the DNS configuration includes a DNS server IP address but does not also include a domain suffix, then any DNS-compatible commands should include the target host’s fully qualified domain name. Refer to Figure C-25 on page C-80.

Switch-Initiated DNS packets go out through the VLAN having the best route to the DNS server, even if a Management VLAN has been configured.

The DNS server address must be manually input. It is not automati- cally determined via DHCP.

C-86