Configuration Guide User guide

FastIron Configuration Guide 969
53-1002494-02
Configuring IP parameters – Layer 3 Switches
Configuring an IPv4 address with a 31-bit subnet mask
To configure an IPv4 address with a 31-bit subnet mask, enter the following commands.
You can configure an IPv4 address with a 31-bit subnet mask on any interface (for example,
Ethernet, loopback, VE, or tunnel interfaces).
Brocade(config)# interface ethernet 1/1/5
Brocade(config-if-e1000-1/5)# ip address 9.9.9.9 255.255.255.254
You can also enter the IP address and mask in the Classless Inter-domain Routing (CIDR) format, as
follows.
Brocade(config-if-e1000-1/1/5)# ip address 9.9.9.9/31
Syntax: [no] ip address <ip-address> <ip-mask>
Syntax: [no] ip address <ip-address>/<subnet mask-bits>
The <ip-address> variable specifies the host address. The <ip-mask> variable specifies the IP
network mask. The <subnet mask-bits> variable specifies the network prefix mask.
To disable configuration for an IPv4 address with a 31-bit subnet mask on any interface, use the no
form of the command.
You cannot configure a secondary IPv4 address with a 31-bit subnet mask on any interface. The
following error message is displayed when a secondary IPv4 address with a 31-bit subnet mask is
configured.
Error: Cannot assign /31 subnet address as secondary
Configuration example
Figure 111 shows the usage of 31- and 24-bit subnet masks in configuring IP addresses.
FIGURE 111 Configured 31- bit and 24-bit subnet masks
Router A is connected to Router B as a point-to-point link with 1.1.1.0/31 subnet. There are only
two available addresses in this subnet, 1.1.1.0 on Router A and 1.1.1.1 on Router B,
Routers B and C are connected by a regular 24-bit subnet. Router C can either be a switch with
many hosts belonging to the 2.2.2.2/24 subnet connected to it, or it can be a router.
Router A
RouterA(config)# interface ethernet 1/1/1
RouterA(config-if-e1000-1/1/1)# ip address 1.1.1.0/31
Router B
RouterB(config)# interface ethernet 1/1/1
RouterB(config-if-e1000-1/1/1)# ip address 1.1.1.1/31
RouterB(config-if-e1000-1/1/1)# exit
ABC
Router
1.1.1.0/31
1.1.1.1/31
2.2.2.1/24
2.2.2.2/24
Router