Figure 82: Enabling Rogue DHCP server detection
DHCP Relay
ZoneDirector's DHCP Relay agent improves network performance by converting DHCP
broadcast traffic to unicast to prevent flooding the Layer 2 network (when Layer 3 Tunnel
Mode is enabled -- DHCP Relay only applies to Tunnel Mode WLANs.)
Typically, when mobile stations acquire IP addresses through DHCP, the DHCP request
and acknowledgment traffic is broadcast to any devices in the same Layer 2 environment.
With Tunnel Mode WLANs, this traffic flood is wasteful in terms of bandwidth and
computing power. When DHCP Relay is enabled on a WLAN, the ZoneDirector relay
agent converts DHCP Discover / Request traffic to unicast UDP packets and sends them
to the DHCP servers, then delivers DHCP Offer / Ack messages from the DHCP server
back to the client.
The traffic flow is as follows:
1.
Client sends DHCP discover broadcast.
2.
AP tunnels this DHCP discover frame to ZoneDirector.
3.
DHCP Relay Agent sends unicast DHCP discover packet to DHCP server.
4.
DHCP server sends DHCP offer to Relay Agent on ZoneDirector.
5.
ZoneDirector sends DHCP Offer back to the AP.
6.
AP sends this Offer to client.
By reducing broadcast flooding, this option allows for higher client capacity in tunneled
WLANs designed for VoIP phones, for example. It also allows for DHCP discovery across
multiple subnets and limits DHCP broadcasts to the client's AP tunnel and radio.
To configure DHCP Relay for tunneled WLANs:
1.
Go to
Configure
>
DHCP Relay
.
2.
Click
Create New
.
3.
Enter a
Name
and
IP address
for the server.
4.
Click
OK
to save your changes. The new server appears in the list.
Ruckus Wireless ZoneDirector™ Release 10.0 User Guide
126
Configuring Security and Other Services
DHCP Relay
