
Configuring IP, ARP, RARP, RIP, and OSPF Services
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308627-14.20 Rev 00
Allowing an All-Zero or All-One Subnet Address
By default, you cannot configure IP interface addresses with a subnet portion
consisting of all zeros or all ones. However, you can configure IP to allow
addresses with all zeros or all ones in the subnet portion. Use this feature with
caution, however, for it can result in an ambiguous address. For example, if an
all-zero subnet address and an all-zero broadcast address are both valid, the router
cannot distinguish an all-subnet broadcast from a directed broadcast for the zero
subnet.
If you enable the use of all-zero and all-one subnet addresses, you must choose
whether to allow the router to broadcast RIP Version 1 updates. If you do not
enable RIP 1 broadcasts on all-zero and all-one subnet addresses, the router
interprets the subnet as an all-subnet broadcast (ASB).
Using the BCC
To allow or deny the use of all-zero or all-one subnet addresses, go to the global IP
prompt (for example,
box; ip
) and enter:
all-subnets
<value>
value
is one of the following:
disabled
(default)
enabled
(no RIP Version 1 updates)
rip1onasb
(RIP Version 1 updates)
For example, the following command enables the use of all-zero or all-one subnet
addresses:
ip#
all-subnets enabled
ip#
4. Set the Default TTL parameter. Click on
Help or see the parameter description on
page A-20.
5. Click on OK. You return to the Configuration Manager
window.
Site Manager Procedure
(continued)
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