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Cisco Security Appliance Command Line Configuration Guide
OL-10088-01
Chapter 19 Applying AAA for Network Access
Configuring Authorization for Network Access
prevents malicious use of a downloadable access list name to gain unauthorized network access. The
Message-Authenticator attribute and its use are defined in RFC 2869, RADIUS Extensions,
available at http://www.ietf.org.
5. If the access list required is less than approximately 4 KB in length, Cisco Secure ACS responds
with an access-accept message containing the access list. The largest access list that can fit in a
single access-accept message is slightly less than 4 KB because some of the message must be other
required attributes.
Cisco Secure ACS sends the downloadable access list in a cisco-av-pair RADIUS VSA. The access
list is formatted as a series of attribute-value pairs that each contain an ACE and are numbered
serially:
ip:inacl#1=ACE-1
ip:inacl#2=ACE-2
.
.
.
ip:inacl#n=ACE-n
An example of an attribute-value pair follows:
ip:inacl#1=permit tcp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
6. If the access list required is more than approximately 4 KB in length, Cisco Secure ACS responds
with an access-challenge message that contains a portion of the access list, formatted as described
above, and an State attribute (IETF RADIUS attribute 24), which contains control data used by
Cisco Secure ACS to track the progress of the download. Cisco Secure ACS fits as many complete
attribute-value pairs into the cisco-av-pair RADIUS VSA as it can without exceeding the maximum
RADIUS message size.
The security appliance stores the portion of the access list received and responds with another
access-request message containing the same attributes as the first request for the downloadable
access list plus a copy of the State attribute received in the access-challenge message.
This repeats until Cisco Secure ACS sends the last of the access list in an access-accept message.
Configuring Cisco Secure ACS for Downloadable Access Lists
You can configure downloadable access lists on Cisco Secure ACS as a shared profile component and
then assign the access list to a group or to an individual user.
The access list definition consists of one or more security appliance commands that are similar to the
extended access-list command (see the “Adding an Extended Access List” section on page 16-5), except
without the following prefix:
access-list acl_name extended
The following example is a downloadable access list definition on Cisco Secure ACS version 3.3:
+--------------------------------------------+
| Shared profile Components |
| |
| Downloadable IP ACLs Content |
| |
| Name: acs_ten_acl |
| |
| ACL Definitions |
| |
| permit tcp any host 10.0.0.254 |
| permit udp any host 10.0.0.254 |
| permit icmp any host 10.0.0.254 |
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