H3C MSR 2600 Configuration Manual page 53

request, the DHCP server selects an address from the primary subnet. If no assignable address is found,
the server selects an address from the secondary subnets in the order they are configured.
In scenarios where the DHCP server and the DHCP clients reside on different subnets and the DHCP
clients obtain IP addresses through a DHCP relay agent, the DHCP server needs to use the same address
pool to assign IP addresses to clients in different subnets. To meet this need, you can specify a primary
subnet and multiple secondary subnets in a DHCP address pool, which are consistent with the subnets
where the relay agent interfaces reside. Upon receiving a DHCP request forwarded by a relay agent, the
DHCP server reads the giaddr field in the request to find the corresponding subnet and selects an IP
address for the client.
Follow these guidelines when you specify a primary subnet and secondary subnets for a DHCP address
pool:
• You can specify only one primary subnet in each address pool. If you use the network command
multiple times, the most recent configuration takes effect.
You can specify a maximum of 32 secondary subnets in each address pool.
•
IP addresses specified by the forbidden-ip command are not assignable in the current address pool,
•
but are assignable in other address pools. IP addresses specified by the dhcp server forbidden-ip
command are not assignable in any address pool.
To specify a primary subnet and secondary subnets for a DHCP address pool:
Step
1. Enter system view.
2. Enter address pool view.
3. Specify the primary subnet.
4. (Optional.) Specify a secondary
subnet.
5. (Optional.) Return to address pool
view.
6. (Optional.) Specify the address
lease duration.
7. (Optional.) Exclude the specified
IP addresses from dynamic
allocation.
8. Return to system view.
Command
system-view
dhcp server ip-pool pool-name
network network-address
[ mask-length | mask mask ]
network network-address
[ mask-length | mask mask ]
secondary
quit
expired { day day [ hour hour
[ minute minute [ second second ] ] ]
| unlimited }
forbidden-ip ip-address&<1-8>
quit
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Remarks
N/A
N/A
By default, no primary subnet
is specified.
By default, no secondary
subnet is specified.
N/A
The default setting is one day.
By default, all the IP
addresses in the DHCP
address pool can be
dynamically allocated.
To exclude multiple address
ranges from the address pool,
repeat this step.
N/A