With Cisco routers, you have the following three choices for viewing the subnet mask.
You can modify how the router displays the subnet mask. In privileged EXEC mode, use the following command:
terminal ip netmask-format <format keyword>
Format keywords are bit-count, decimal, or hexadecimal.
When setting up a network for IP, you will have to make various decisions about the addresses used on the network. Use the following process to identify and assign IP addresses throughout your network.
- Identify the number of network addresses. Each network segment will require its own network (subnet) address. In addition, each WAN connection must have its own network address (typically assigned by the WAN service provider).
- Identify the number of hosts for each subnet. You will need one IP address for each device. Be sure to include an IP address for each router interface.
- Calculate the subnet mask that will subdivide your network.
- Identify the valid subnet addresses, and assign them to network segments.
- Identify valid IP addresses on each subnet (i.e. the host address range). Assign IP addresses to hosts, or plan on using DHCP to dynamically assign IP addresses.
You can also assign multiple IP addresses to a single interface. To do this, use the secondary parameter with the ip address command as follows:
ip address 10.10.10.2 255.0.0.0 secondary