Filtering Ip Packets At The Ip Interfaces; Creating Standard And Extended Ip Access Lists - Cisco Catalyst 8540 MSR Configuration Manual

Chapter 12 Using Access Control
Filter Switch(config)# atm filter-set filter_1 permit default
Filter Switch(config)# atm filter-expr exp1 src filter_1
Filter Switch(config)#
Filter Switch(config)# interface atm 1/0/0
Filter Switch(config-if)# atm access-group exp1 in
Filter Switch(config-if)# end
Filter Switch# show atm filter-set
ATM filter set filter_1
deny
permit default
Filter Switch# show atm filter-expr
exp1 = src filter_1

Filtering IP Packets at the IP Interfaces

IP packet filtering helps control packet movement through the network. Such control can help limit
network traffic and restrict network use by certain users or devices. To permit or deny packets from
crossing specified IP interfaces, Cisco provides access lists.
You can use access lists for the following reasons:
•
•
•
This section summarizes how to create IP access lists and how to apply them.
Note This section applies to the IP interfaces only.
An access list is a sequential collection of permit and deny conditions that apply to IP addresses. The
ATM switch router software tests addresses against the conditions in an access list one by one. The first
match determines whether the software accepts or rejects the address. Because the software stops testing
conditions after the first match, the order of the conditions is critical. If no conditions match, the
software rejects the address.
The two steps involved in using access lists follow:
Create an access list by specifying an access list number and access conditions.
Step 1
Apply the access list to interfaces or terminal lines.
Step 2
These steps are described in the following sections:
•
•

Creating Standard and Extended IP Access Lists

The ATM switch router software supports three styles of access lists for IP interfaces:
•
OL-7396-01
47.0091.8100.0000.2222.2222.ffff...
index 2
Control the transmission of packets on an IP interface
Control virtual terminal line access
Restrict contents of routing updates
"Creating Standard and Extended IP Access Lists" section on page 12-9
"Applying an IP Access List to an Interface or Terminal Line" section on page 12-11
Standard IP access lists use source addresses for matching operations.
Filtering IP Packets at the IP Interfaces
index 1
ATM Switch Router Software Configuration Guide
12-9