Dell FCX624-I Laptop User Manual


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868 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Configuring IP parameters – Layer 2 Switches
26
NOTE
The DHCP relay function of the connecting router must be turned on.
FIGURE 137 DHCP offers are forwarded back toward the requestors
NOTE
When DHCP Assist is enabled on any port, Layer 2 broadcast packets are forwarded by the CPU.
Unknown unicast and multicast packets are still forwarded in hardware, although selective packets
such as IGMP are sent to the CPU for analysis. When DHCP Assist is not enabled, Layer 2 broadcast
packets are forwarded in hardware.
Configuring DHCP Assist
You can associate a gateway list with a port. You must configure a gateway list when DHCP Assist is
enabled on a Layer 2 Switch. The gateway list contains a gateway address for each subnet that will
be requesting addresses from a DHCP server. The list allows the stamping process to occur. Each
gateway address defined on the Layer 2 Switch corresponds to an IP address of the router interface
or other router involved.
Step 4:
DHCP Server extracts the gateway
address from each packet and
assigns IP addresses for each
host within the appropriate
range.
DHCP response with IP addresses
for Subnets 1, 2, 3 and 4
Step 5:
IP addresses are distributed
to the appropriate hosts.
192.95.5.10
200.95.6.15
202.95.1.35
202.95.5.25
Host 1
Host 2
192.95.5.x
Subnet 1
200.95.6.x
Subnet 2
Host 3
Host 4
202.95.1.x
Subnet 3
202.95.5.x
Subnet 4
Router
DHCP
Server
207.95.7.6
192.95.5.10
200.95.6.15
202.95.1.35
202.95.5.25
Layer 2 Switch
Hub