Cisco CRS-1 - Carrier Routing System Router Getting Started Manual page 63

Chapter 3 CLI Tips, Techniques, and Shortcuts
The following example adds an entry to access list 99. The added entry denies access to all hosts on
subnet 172.0.0.0and ignores bits for IPv4 addresses that start within the range of 0 to 255. The following
steps provide an example of on-screen command help:
Enter the access-list command, followed by a space and a question mark, to list the available options for
Step 1
the command:
RP/0/RP0/CPU0:router(config)# access-list ?
<1-199>
<1300-2699>
The number ranges (within the angle brackets) are inclusive ranges.
Note
Enter the access list number 99, followed by a space and another question mark, to display the arguments
Step 2
that apply to the keyword and brief explanations:
RP/0/RP0/CPU0:router(config)# access-list 99 ?
<1-2147483647>
deny
permit
remark
<cr>
RP/0/RP0/CPU0:router(config)# access-list 99 deny ?
A.B.C.D Address to match
Generally, uppercase letters represent variables (arguments). Enter the IP address, followed by a space
Step 3
and a question mark (?), to list additional options:
RP/0/RP0/CPU0:router(config)# access-list 99 deny 172.31.134.0 ?
A.B.C.D Mask of bits to ignore
<cr>
In this output, A.B.C.D indicates that use of a mask is allowed. The mask is a method for matching IP
addresses or ranges of IP addresses.
For example, a mask of 255.0.0.0 matches any number in the range from 0 to 255 that appears in the first
octet of an IP address. Enter the mask, followed by a space and a question mark (?) to list further options.
RP/0/RP0/CPU0:router(config)# access-list 99 deny 172.31.134.0 255.0.0.0 ?
<cr>
The <cr> symbol by itself indicates that there are no more keywords or arguments. Press Return to
Step 4
execute the command:
RP/0/RP0/CPU0:router(config)# access-list 99 deny 172.31.134.0 255.0.0.0
Note The configuration does not become active until you enter the commit command to add the target
configuration to the running configuration.
IP Access list
IP Access list
Sequence number for this entry
Specifies packets to reject
Specifies packets to forward
Comment for access list
Cisco CRS-1 Series Carrier Routing System Getting Started Guide
CLI Tips and Shortcuts
3-3