user manual

7-20 Administrator’s Handbook
This screen consists of between two and eight rows of four columns each. There are exactly as many rows as
there are Ethernet IP subnets configured on the IP Subnets screen.
• The Subnet (# host addrs) column is non-selectable and non-editable. It indicates the network address of
the Ethernet IP subnet for which an address pool is being configured and the number of host addresses
available on the subnet. The network address is equal to the gateway’s IP address on the subnet
bitwise-ANDed with the subnet mask. The host address count is equal to the subnet size minus three,
since one address is reserved for the network address, one for the subnet broadcast address, and one for
the gateway’s interface address on the subnet.
You can edit the remaining columns in each row.
• The 1st Client Addr and Clients columns allow you to specify the base and extent of the address serving
pool for a particular subnet. Entering 0.0.0.0 for the first client address or 0 for the number of clients
indicates that no addresses will be served from the corresponding Ethernet IP subnet.
• The Client Gateway column allows you to specify the default gateway address that will be provided to
clients served an address from the corresponding pool. The value defaults to the Router’s IP address on
the corresponding subnet (or the Router’s default gateway, if that gateway is located on the subnet in
question). You can override the value by entering any address that is part of the subnet.
DHCP, BootP, and dynamic WAN clients may receive an address from any one of the address serving pools
configured on this screen.
Numerous factors influence the choice of served address. It is difficult to specify the address that will be
served to a particular client in all circumstances. However, when the address server has been configured, and
the clients involved have no prior address serving interactions, the Router will generally ser ve the first unused
address from the first address pool with an available address. The Router starts from the pool on the first row
and continues to the pool on the last row of this screen.
Once the address server and/or the clients have par ticipated in address serving transactions, different rules
apply:
IP Address Pools
Subnet (# host addrs) 1st Client Addr Clients Client Gateway
--------------------- --------------- ------- --------------
192.128.117.0 (253) 192.128.117.196 16 192.128.117.162
192.129.117.0 (253) 192.129.117.110 8 192.129.117.4