Administrator Guide

Layer 2 Switching Commands 510
Default Configuration
By default, the switch uses the assigned switch IP address as the source IP
address for DNS packets. This address is either the IP address assigned to the
VLAN from which the DNS packet originates or the out-of-band interface IP
address.
Command Mode
Global Configuration mode
User Guidelines
The source interface must have an assigned IP address (assigned either
manually or via another method such as DHCP).
The use of a source interface allows firewalls devices to identify DNS packets
ascoming from a specific switch. If the source interface is not specified, the
primary address of the outbound interface is used as the source interface. If
the specified interface is down, the DNS client falls back to it’s original
(unconfigured) behavior.
Command History
Introduced in version 6.3.0.1 firmware.
Example
The following example configures a source interface for a VLAN interface
that obtains its address via DHCP:
console#configure
console(config)#interface vlan 1
console(config-if-vlan1)#ip address dhcp
console(config-if-vlan1)#exit
console(config)#ip name-server source-interface vlan 1
This example configures a source interface for a loopback interface. Using a
loopback address is the recommended method for assigning a source
interface.
console#configure
console(config)#interface loopback 0
console(config-if-vlan1)#ip address 129.168.0.13 /32
console(config-if-vlan1)#exit
console(config)#ip name-server source-interface vlan 1
2CSNXXX_SWUM204.book Page 510 Monday, January 25, 2016 1:25 PM