IP Routing Features
Configuring DHCP Relay
■routing switch access to an Option 82 DHCP server on a different subnet than the clients requesting DHCP Option 82 support
■one IP Helper address configured on each VLAN supporting DHCP clients
General
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| DHCP |
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| Relay Agent “1” |
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| Option 82 |
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| Switch |
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| Server |
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| Switch |
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| VLAN 3 | VLAN 4 |
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| Option 82 Enabled |
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| Switch |
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| Client |
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| VLAN 3 | VLAN 2 | Relay Agent “2” |
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| No Option 82 |
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| Relay Agent “3” |
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| Switch |
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| VLAN 1 | VLAN 2 |
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| Option 82 Enabled |
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| Client |
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Relay Agent 1 adds an Option 82 field to a client request, and then forwards the request toward the server. This includes any client requests received from Relay Agent 2 without an Option 82 field.
Note: DHCP Option 82 does not operate with clients on VLAN 4 because DHCP requests from these clients are not routed.
Relay Agent 2 does not add an Option 82 field to client requests before forwarding the requests. However, any client requests received from Relay Agent 3 will be forwarded with the Option 82 fields that were added by Relay Agent 3.
Relay Agent 3 adds an Option 82 field to a client request and then forwards the request.
Figure