Ruckus Wireless ZoneDirector 3000, User Manual, Page: 98 / 430

Configuring DHCP Relay
Configuring SNMP Support
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Ruckus Wireless, Inc.
Configuring 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 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.