Bootp And Dhcp Relay Parameter Configuration - Brocade Communications Systems ICX 6650 Configuration Manual

To configure a helper address on an interface 2 on chassis module 1, enter the following
commands.
Brocade(config)# interface ethernet 1/1/2
Brocade(config-if-e10000-1/1/2)# ip helper-address 1 192.168.7.6
The commands in this example change the CLI to the configuration level for port 1/1/2, then add a
helper address for server 192.168.7.6 to the port. If the port receives a client request for any of
the applications that the Layer 3 Switch is enabled to forward, the Layer 3 Switch forwards the
client request to the server.
Syntax: ip helper-address num ip-addr
The num parameter specifies the helper address number and can be from 1 through 16.
The ip-addr command specifies the server IP address or the subnet directed broadcast address of
the IP subnet the server is in.

BootP and DHCP relay parameter configuration

A host on an IP network can use BootP or DHCP to obtain its IP address from a BootP/DHCP server.
To obtain the address, the client sends a BootP or DHCP request. The request is a subnet directed
broadcast and is addressed to UDP port 67. A limited IP broadcast is addressed to IP address
255.255.255.255 and is not forwarded by the Brocade Layer 3 Switch or other IP routers.
When the BootP or DHCP client and server are on the same network, the server receives the
broadcast request and replies to the client. However, when the client and server are on different
networks, the server does not receive the client request, because the Layer 3 Switch does not
forward the request.
You can configure the Layer 3 Switch to forward BootP/DHCP requests. To do so, configure a
helper address on the interface that receives the client requests, and specify the BootP/DHCP
server IP address as the address you are helping the BootP/DHCP requests to reach. Instead of
the server IP address, you can specify the subnet directed broadcast address of the IP subnet the
server is in.
BootP and DHCP relay parameters
The following parameters control the Layer 3 Switch forwarding of BootP and DHCP requests:
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Brocade ICX 6650 Layer 3 Routing Configuration Guide
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Helper address – The BootP/DHCP server IP address. You must configure the helper address
on the interface that receives the BootP/DHCP requests from the client. The Layer 3 Switch
cannot forward a request to the server unless you configure a helper address for the server.
Gateway address – The Layer 3 Switch places the IP address of the interface that received the
BootP/DHCP request in the request packet Gateway Address field (sometimes called the
Router ID field). When the server responds to the request, the server sends the response as a
unicast packet to the IP address in the Gateway Address field. (If the client and server are
directly attached, the Gateway ID field is empty and the server replies to the client using a
unicast or broadcast packet, depending on the server.)
By default, the Layer 3 Switch uses the lowest-numbered IP address on the interface that
receives the request as the Gateway address. You can override the default by specifying the IP
address you want the Layer 3 Switch to use.
Configuring IP parameters – Layer 3 Switches
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