AAA LDAP Configuration Guide Cisco IOS Release 15 M and T

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Updated:
March 21, 2010

Chapter: Configuring LDAP


Configuring LDAP

First Published: March 19, 2010
Last Updated: March 19, 2010

Lightweight Directory Access Protocol (LDAP) is integrated into Cisco IOS software as a AAA protocol alongside the existing AAA protocols such as RADIUS, TACACS+, Kerberos, and Diameter. AAA framework provides tools and mechanisms such as method lists, server groups, and generic attribute lists that enable an abstract and uniform interface to AAA clients irrespective of actual protocol used for communication with the AAA server. LDAP supports authentication and authorization functions for AAA.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Configuring LDAP" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for Configuring LDAP

•Restrictions for Configuring LDAP

•Information About LDAP

•How to Configure LDAP

•Configuration Examples for LDAP

•Additional References

•Feature Information for Configuring LDAP

Prerequisites for Configuring LDAP

If you are using a secure Transport Layer Security (TLS) secure connection, you must configure X.509 certificates.

Restrictions for Configuring LDAP

LDAP client implementation has the following restrictions:

•Bind, search, and compare operations are supported.

•LDAP referrals are not supported.

•Unsolicited messages or notifications from LDAP server are not handled.

Information About LDAP

To configure LDAP, you should understand the following concepts:

•Transport Layer Security

•LDAP Operations

•LDAP Dynamic Attribute Mapping

Transport Layer Security

TLS is an application-level protocol that enables secure transactions of data through privacy, authentication, and data integrity. It relies upon certificates, public keys, and private keys for clients to prove the identity. Certificates are issued by Certificate Authorities (CAs). Each certificate includes the name of the authority that issued it, the name of the entity to which the certificate was issued, the entity's public key, and time stamps that indicate the certificate's expiration date. TLS support for LDAP is mentioned in RFC 2830 as an extension to the LDAP protocol.

LDAP Operations

The following operations are supported in LDAP:

•Bind

•Search

•Compare

Bind

The bind operation is used to authenticate a user to the server. It is used to start a connection with the LDAP server. LDAP is a connection-oriented protocol. The client specifies the protocol version and the client authentication information. LDAP supports the following binds:

•Authenticated bind

•Anonymous bind

An authenticated bind is performed when a root distinguished name (DN) and password are available. In the absence of a root DN and password, an anonymous bind is performed. In LDAP deployments, the search operation is performed first and the bind operation later. This is because, if a password attribute is returned as part of the search operation, then the password verification can be done locally on an LDAP client. Thus, there is no need to perform an extra bind operation. If a password attribute is not returned, bind operation can be performed later. Another advantage of performing a search operation first and bind operation later is that the distinguished name (DN) received in the search result can be used as the user DN instead of forming a DN by prefixing the username (cn attribute) with base DN. All entries stored in an LDAP server have a unique distinguished name (DN). The DN consists of two parts: Relative Distinguished Name (RDN) and location within the LDAP server where the record resides.

Most of the entries that you store in an LDAP server will have a name, and the name is frequently stored in the cn (Common Name) attribute. Because every object has a name, most objects you store in an LDAP will use their cn value as the basis for their RDN.

Search

A search operation is used to search the LDAP server. The client specifies the starting point (base DN) of the search, the search scope (either the object, its children, or the subtree rooted at the object), and a search filter.

For authorization requests, the search operation is directly performed without a bind operation. The LDAP server can be configured with certain privileges for the search operation to succeed. This privilege level is established with the bind operation.

An LDAP search operation can return multiple user entries for a specific user. In such cases, the LDAP client returns an appropriate error code to AAA. To avoid these errors, appropriate search filters that help to match a single entry must be configured.

Compare

The compare operation is used to replace a bind request with a compare request for an authentication. The compare operation helps to maintain the initial bind parameters for the connection.

LDAP Dynamic Attribute Mapping

LDAP is a powerful and flexible protocol for communication with AAA servers. LDAP attribute maps provide a method to cross-reference the attributes retrieved from a server to Cisco attributes supported by the security appliances.

When a user authenticates a security appliance, the security appliance, in turn, authenticates to the server and uses the LDAP protocol to retrieve the record for that user. The record consists of LDAP attributes associated with fields displayed on the user interface of the server. Each attribute retrieved includes a value that was entered by the administrator who updates the user records.

How to Configure LDAP

This section contains the following procedures:

•Configuring Router-to-LDAP Server Communication (required)

•Configuring LDAP Protocol Parameters (optional)

•Configuring a AAA Server Group (optional)

•Configuring Search and Bind Operations for an Authentication Request (optional)

•Configuring a Dynamic Attribute Map on an LDAP Server (optional)

Configuring Router-to-LDAP Server Communication

Perform this task to configure router-toLDAP server communication.

The LDAP host is normally a multiuser system running LDAP server software such as Active Directory (Microsoft) and OpenLDAP. Configuring router-to-LDAP server communication can have several components:

•Hostname or IP address

•Port number

•Timeout period

•Base DN

SUMMARY STEPS

1. enable

2. configure terminal

3. ldap server name

4. ipv4 ipv4-address

5. transport port port-number

6. timeout retransmit seconds

7. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

ldap server name

Example:

Router(config)# ldap server server1

Configures a device to use the LDAP protocol and enters LDAP server configuration mode.

Step 4 

ipv4 ipv4-address

Example:

Router(config-ldap-server)# ipv4 10.0.0.1

Specifies the LDAP server IP address using IPv4.

Step 5 

transport port port-number

Example:

Router(config-ldap-server)# transport port 200

Configures the transport protocol for connecting to the LDAP peer.

Step 6 

timeout retransmit seconds

Example:

Router(config-ldap-server)# timeout retransmit 20

Specifies the number of seconds a router waits for a reply to an LDAP request before retransmitting the request.

Step 7 

exit

Example:

Router(config-ldap-server)# exit

Exits the LDAP server configuration mode.

Configuring LDAP Protocol Parameters

Perform this task to configure the LDAP protocol parameters.

SUMMARY STEPS

1. enable

2. configure terminal

3. ldap server name

4. bind authenticate root-dn password [0 string | 7 string] string

5. search-filter user-object-type string

6. base-dn string

7. mode secure [no-negotiation]

8. secure cipher secure cipher 3des-ede-cbc-sha

9. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

ldap server name

Example:

Router(config)# ldap server server1

Configures a device as an LDAP protocol and enters LDAP server configuration mode.

Step 4 

bind authenticate root-dn password [0 string | 7 string] string

Example:

Router(config-ldap-server)# bind authenticate root-dn "cn=administrator,cn=users,dc=nac-blr2,dc=examp le,dc=com password"

Specifies the shared secret text string used between the router and an LDAP server. Use the 0 line option to configure an unencrypted shared secret. Use the 7 line option to configure an encrypted shared secret.

Step 5 

search-filter user-object-type string

Example:

Router(config-ldap-server)# search-filter user-object-type name

Specifies the search filter to be used in the search requests.

Step 6 

base-dn string

Example:

Router(config-ldap-server)# base-dn "dc=sns,dc=example,dc=com"

Specifies the base DN of the search.

Step 7 

mode secure [no-negotiation]

Example:

Router(config-ldap-server)# mode secure no-negotiation

Configures LDAP to initiate the TLS connection and specifies the secure mode.

Step 8 

secure cipher 3des-ede-cbc-sha

Example:

Router(config-ldap-server)# secure cipher 3des-ede-cbc-sha

Specifies the ciphersuite in case of secure connection.

Step 9 

exit

Example:

Router(config-ldap-server)# exit

Exits the LDAP server configuration mode.

Configuring a AAA Server Group

Perform this task to configure a AAA server group.

Configuring the router to use AAA server groups enables you to group existing servers. You need to select a subset of the configured server hosts and use them for a particular service. A server group is used in conjunction with a global server-host list. The server group lists the IP addresses of the selected server hosts. Server groups also can include multiple host entries for the same server, as long as each entry has a unique identifier.

If two different host entries on the same LDAP server are configured for the same service (for example, accounting) the second host entry configured acts as failover backup to the first one. Using this example, if the first host entry fails to provide accounting services, the network access server will try the second host entry configured on the same device for accounting services. (The LDAP host entries will be tried in the order in which they are configured.) To define a server host with a server group name, enter the following commands. The listed server must exist in global configuration mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. aaa new-model

4. aaa group server ldap group-name

5. server name

6. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

aaa new-model

Example:

Router(config)# aaa new-model

Enables AAA.

Step 4 

aaa group server ldap group-name

Example:

Router(config)# aaa group server ldap name1

Defines the AAA server group with a group name and enters the LDAP server group configuration mode. All members of a group must be the of same type; that is, RADIUS, LDAP, or TACACS+.

Step 5 

server name

Example:

Router(config-ldap-sg)# server server1

Associates a particular LDAP server with the defined server group. Each security server is identified by its IP address and UDP port number.

Step 6 

exit

Example:

Router(config-ldap-server)# exit

Exits LDAP server group configuration mode.

Configuring Search and Bind Operations for an Authentication Request

Perform this task to configure search and bind operations for an authentication request:

SUMMARY STEPS

1. enable

2. configure terminal

3. ldap server name

4. authentication bind-first

5. authentication compare

6. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

ldap server name

Example:

Router(config)# ldap server server1

Configures a device as an LDAP protocol and enters LDAP server configuration mode.

Step 4 

authentication bind-first

Example:

Router(config-ldap-server)# authentication bind-first

Configures the sequence of search and bind operation for an authentication request.

Step 5 

authentication compare

Example:

Router(config-ldap-server)# authentication compare

Replaces the bind request with the compare request for authentication.

Step 6 

exit

Example:

Router(config-ldap-server)# exit

Exits the LDAP server configuration mode.

Configuring a Dynamic Attribute Map on an LDAP Server

Perform this task to configure a dynamic attribute map on an LDAP server.

You must create LDAP attribute maps that map your existing user-defined attribute names and values to Cisco attribute names and values that are compatible with the security appliance. You can then bind these attribute maps to LDAP servers or remove them as required. See the chapter "User-Based Firewall support" in Cisco IOS Security Configuration Guide: Securing the Data Plane for more information about user-based firewalls.

Note To use the attribute mapping features correctly, you need to understand the Cisco LDAP attribute names and values as well as the user-defined attribute names and values.

SUMMARY STEPS

1. enable

2. configure terminal

3. ldap attribute map map-name

4. map type ldap-attr-type aaa-attr-type

5. exit

6. ldap server name

7. ipv4 ipv4-address

8. bind authenticate root-dn password [0 string | 7 string] string

9. base-dn string

10. attribute map map-name

11. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

ldap attribute map map-name

Example:

Router(config)# ldap attribute-map map1

Configures dynamic LDAP attribute map and enters attribute-map configuration mode.

Step 4 

map type ldap-attr-type aaa-attr-type

Example:

Router(config-attr-map)# map type department Engineering group1

Defines an attribute map.

Step 5 

exit

Example:

Router(config-attr-map)# exit

Exits the attribute-map configuration mode.

Step 6 

ldap server name


Example:

Router(config)# ldap server ldap_dir_1

Specifies the LDAP server name and enters into the LDAP server configuration mode.

Step 7 

ipv4 ipv4-address

Example:

Router(config-ldap-server)# ipv4 10.0.0.1

Specifies the IP address of the LDAP server.

Step 8 

bind authenticate root-dn user-name password [0 string | 7 string] string

Example:

Router(config-ldap-server)# bind authenticate root-dn "cn=user1,cn=users,dc=sns,dc=example,dc=com"

Binds the attribute testmap to the LDAP server.

Step 9 

base-dn string

Example:

Router(config-ldap-server)# base-dn "dc=sns,dc=example,dc=com"

(Optional) Configures the base DN that you want to use to perform search operations in the LDAP server.

Step 10 

attribute map map-name

Example:

Router(config-ldap-server)# attribute map att_map_1

Attaches the attribute map to a particular LDAP server.

Step 11 

exit

Example:

Router(config-ldap-server)# exit

Exits server group configuration mode.

Monitoring and Maintaining LDAP

To monitor and maintain LDAP scalability enhancements, use the following commands in privileged EXEC mode. The following commands can be entered in any order.

Command
Purpose

Router# clear ldap server

Clears the TCP connection with the LDAP server.

Router# debug ldap

Displays information associated with LDAP.

Router# show ldap server

Displays the LDAP server state information and various other counters for the server.

Router# show ldap attributes

Displays information about default LDAP attribute mapping.

Configuration Examples for LDAP

This section provides the following configuration examples:

•LDAP Server Communication: Example

•LDAP Protocol Parameters: Example

•AAA Server Group: Example

•Search and Bind Operations for an Authentication Request: Example

•Dynamic LDAP Attribute Map and LDAP Server: Example

LDAP Server Communication: Example

The following example shows how to create server group server1 and specify the IP address, transport port, and retransmit values: 

ldap server server1

server1 10.0.0.1 transport port 200 retransmit 600 failover retransmit 600

LDAP Protocol Parameters: Example

The following example shows how to configure the LDAP parameters: 

ldap server server1 

 bind authenticate root-dn "cn=administrator,cn=users,dc=nac-blr2,dc=cisco,dc=com password 
123"

 search-filter user-object-type objectclass

 base-dn "dc=sns,dc=example,dc=com"

 mode secure no-negotiation

 secure cipher 3des-ede-cbc-sha

AAA Server Group: Example

The following example shows how to configure the AAA server group: 

aaa new-model

 aaa group server ldap server1

Search and Bind Operations for an Authentication Request: Example

The following example shows how to configure the sequence of search and bind for an authentication request: 

ldap server server1

 authentication bind-first

 authentication compare

Dynamic LDAP Attribute Map and LDAP Server: Example

The following example shows how to attach the attribute map to a particular LDAP server: 

ldap attribute-map att_map_1

 map type department element-req-qos

exit

ldap server ldap_dir_1

ipv4 10.0.0.1

 bind authenticate root-dn cn=administrator,cn=users,dc=nac-blr2,dc=example,dc=com 
password example123

 base-dn "dc=sns,dc=example,dc=com"

 attribute map att_map_1

Additional References

The following sections provide references related to configuring the LDAP feature.

Related Documents

Related Topic
Document Title

AAA

"Configuring Authentication" module


Standards

Standard
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs


RFCs

RFC
Title

RFC 2830

Lightweight Directory Access Protocol (v3): Extension for Transport Layer Security

RFC 4511

Lightweight Directory Access Protocol (LDAP)

RFC 4513

Lightweight Directory Access Protocol (LDAP): Authentication Methods and Security Mechanisms

RFC 4514

Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names

RFC 4515

Lightweight Directory Access Protocol (LDAP): String Representation of Search Filters

RFC 4517

Lightweight Directory Access Protocol (LDAP): Syntaxes and Matching Rules

RFC 4519

Lightweight Directory Access Protocol (LDAP): Schema for User Applications


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Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html


Feature Information for Configuring LDAP

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for Configuring LDAP 

Feature Name
Releases
Feature Information

LDAP integration with Active Directory

15.1(1)T

LDAP is a standard-based protocol used to access directories. It is based on client server model similar to RADIUS. LDAP is deployed on Cisco devices to send authentication requests to a central LDAP server that contains all user authentication and network service access information.

This feature provides authentication and authorization support for AAA.

The following sections provide information about this feature:

•Information About LDAP

•Configuring Router-to-LDAP Server Communication

•Configuring LDAP Protocol Parameters

•Configuring a AAA Server Group

•Configuring Search and Bind Operations for an Authentication Request

The following commands were introduced or modified: aaa group server ldap, authentication bind-first, authentication compare, bind authenticate, base-dn, clear ldap server, debug ldap, ipv4, mode secure, ldap server, search-filter, secure cipher, show ldap server, transport port, timeout, retransmit.

LDAP Active Directory Support for Authproxy

15.1(1)T

This feature enables the authentication proxy to authenticate and authorize the users with Active Directory servers using LDAP.

The following sections provide information about this feature:

•LDAP Dynamic Attribute Mapping

•Configuring a Dynamic Attribute Map on an LDAP Server

The following commands were introduced or modified: map type, attribute map.


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