Dhcp Relay Mode; Configuration Requirements - Allied Telesis SwitchBlade x3100 Series Manual

DHCP Relay Mode

received an IP address, with the new one. This means that if there are 20 DHCP requests in progress from the
same (network) interface and none of the 20 have completed (have not received an ACK/NACK), and the 21st
DHCP request comes in, the 21st DHCP request will be dropped.
7.2.2.9 DHCP Relay / Snooping on Network Interfaces
Counters are displayed and reset on an interface basis.
Note:
Upon receiving a (client side) DHCP packet without option 82, DHCP Relay will add option 82 and forward
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the DHCP packet to the list of servers.
Upon receiving a (client side) DHCP packet without option 82, DHCP Snooping will add option 82 and
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flood the DHCP packet out the other network interfaces that are members of the VLAN.
DHCP Relay/Snooping will not install filters based on the IP address received from the DHCP server.
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DHCP Relay/Snooping will not auto-age out the IP filters based on the lease time.
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7.2.3 DHCP Relay Mode
7.2.3.1 Overview
Figure 7-3 shows how multiple DHCP Relay instances could be used. The DHCP Relay instance provides
VLAN-level control. However, there is a simpler level of provisioning possible:
For users that require a different set of configuration data (DHCP Server list, Agent Remote ID, CID for-
1.
mat) for each VLAN, they could create separate DHCP Relay Instances and map one VLAN to each
Instance.
For users that want to have a set of VLANs use the same DHCP configuration, they could create the
2.
required number of instances and then map one or more VLANs to each DHCP Instance. Each DHCP
Instance could match a different ISP.
Users that only require one DHCP Instance only need to provision one instance and have all VLANs map to
3.
that one instance.

7.2.3.2 Configuration Requirements

The following configuration rules apply:
You must use the inband management configuration.
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Caution: Use of the out-of-band management interface will prevent DHCP relay from successfully functioning;
the symptoms will be the DHCP server receives the message from the SBx3112, but when the
SBx3112 receives the messages back from the server, it won't be able to handle them properly and
will drop them.
The Inband MGMT VLAN can be non-UFO.
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Software Reference for SwitchBlade x3100 Series Switches (Network Management)
Introduction
7-7