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Configuring and Managing IP Interfaces 105
The DHCP client is enabled by default on an unconfigured WXR100 when
the factory reset switch is pressed and held during power on. The DHCP
client is disabled by default on all other switch models, and is disabled on
a WXR100 if the switch is already configured or the factory reset switch is
not pressed and held during power on.
You can enable the DHCP client on one VLAN only.
MSS also has a configurable DHCP server. (See “Configuring the DHCP
Server” on page 665.) You can configure a DHCP client and DHCP server
on the same VLAN, but only the client or the server can be enabled. The
DHCP client and DHCP server cannot both be enabled on the same VLAN
at the same time.
How MSS Resolves Conflicts with Statically Configured IP
Parameters MSS compares the IP parameter values already configured
on the switch with the values received from the DHCP server, and resolves
any conflicts as follows:
IP address—If the VLAN also has a statically configured IP address,
MSS uses an address from the DHCP server instead of the statically
MSS sends an ARP for the IP address offered by the DHCP server to
verify that the address is not already in use.
If the address is not in use, MSS configures the VLAN that has the
DHCP client enabled with the IP address received from the DHCP
server. MSS then configures the other values as follows:
Default router—MSS adds a default route for the gateway, with
a metric of 10.
DNS domain name and DNS server IP address—If the default
domain name and DNS server IP address are already configured
on the switch, and DNS is enabled, the configured values are
used. Otherwise, the values received from the DHCP server are
If the address offered by the DHCP server is already in use, MSS
sends a DHCP Decline message to the server and generates a log
If the address is in a subnet that is already configured on another
VLAN on the switch, MSS sends a DHCP Decline message to the
server and generates a log message.