- Read Me First
- Configuring the Cisco IOS XE DHCP Server
- Configuring the DHCP Server On-Demand Address Pool Manager
- Configuring the Cisco IOS XE DHCP Relay Agent
- DHCP Relay Server ID Override and Link Selection Option 82 Suboptions
- DHCP Server RADIUS Proxy
- Configuring the Cisco IOS XE DHCP Client
- Configuring DHCP Services for Accounting and Security
- ISSU and SSO--DHCP High Availability Features
- DHCPv6 Relay and Server - MPLS VPN Support
- IPv6 Access Services: DHCPv6 Relay Agent
- IPv6 Access Services: Stateless DHCPv6
- IPv6 Access Services: DHCPv6 Prefix Delegation
- DHCP for IPv6 Broadband
- DHCPv6 Server Stateless Autoconfiguration
- DHCP Server MIB
- Finding Feature Information
- Prerequisites for DHCP Server RADIUS Proxy
- Restrictions for DHCP Server RADIUS Proxy
- Information About DHCP Server RADIUS Proxy
- How to Configure DHCP Server RADIUS Proxy
- Configuration Examples for DHCP Server Radius Proxy
- Additional References
- Technical Assistance
- Feature Information for DHCP Server RADIUS Proxy
- Glossary
DHCP Server RADIUS Proxy
The Dynamic Host Configuration Protocol (DHCP) Server RADIUS Proxy is a RADIUS-based address assignment mechanism in which a DHCP server authorizes remote clients and allocates addresses based on replies from a RADIUS server.
- Finding Feature Information
- Prerequisites for DHCP Server RADIUS Proxy
- Restrictions for DHCP Server RADIUS Proxy
- Information About DHCP Server RADIUS Proxy
- How to Configure DHCP Server RADIUS Proxy
- Configuration Examples for DHCP Server Radius Proxy
- Additional References
- Technical Assistance
- Feature Information for DHCP Server RADIUS Proxy
- Glossary
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for DHCP Server RADIUS Proxy
Before you can configure the DHCP Server RADIUS Proxy, you must be running DHCPv4 or a later version. For information about release and platform support, see "Feature Information for DHCP Server RADIUS Proxy".
Restrictions for DHCP Server RADIUS Proxy
The DHCP Server RADIUS Proxy supports only one address authorization pool on the router.
Information About DHCP Server RADIUS Proxy
- DHCP Server RADIUS Proxy Overview
- DHCP Server RADIUS Proxy Architecture
- DHCP Server and RADIUS Translations
- RADIUS Profiles for DHCP Server RADIUS Proxy
DHCP Server RADIUS Proxy Overview
The DHCP Server RADIUS Proxy feature is an address allocation mechanism for RADIUS-based authorization of DHCP leases. This feature supports DHCP options 60 and 121.
The DHCP server passes client information to a RADIUS server.
The RADIUS server returns all required information to the DHCP server as RADIUS attributes.
The DHCP server translates the RADIUS attributes into DHCP options, and sends this information back to RADIUS in a DHCP OFFER message.
DHCP binding is synchronized after the RADIUS server authorizes the client session.
If a local pool and an authorization pool are configured on the router, the DHCP server can assign addresses from both pools for different client interfaces.
DHCP Server RADIUS Proxy Architecture
The allocation of addresses in a DHCP and RADIUS solution occurs as follows:
The client accesses the network from a residential gateway and sends a DHCP DISCOVER broadcast message to the relay agent. The DHCP DISCOVER message contains the client IP address, hostname, vendor class identifier, and client identifier.
The relay agent sends a DHCP DISCOVER unicast message containing the following information to the router: - Relay agent information (option 82) with the remote ID suboption containing the inner and outer VLAN IDs
- Client information in the DHCP DISCOVER packet
The router determines the address of the DHCP server from the IP helper address on the interface that receives the DHCP packet.
RADIUS receives an access-request message to translate the DHCP options to RADIUS attributes.
RADIUS responds with an access-accept message, and delivers the following attributes to the DHCP server: - Framed-IP-Address
- Framed-IP-Netmask
- Session-Timeout
- Session-Duration
The DHCP server sends an OFFER unicast message containing the following translations from the RADIUS server access-accept message to the client: - Framed-IP-Address inserted into the DHCP header.
- Framed-IP-Netmask inserted into DHCP option 1 (subnet mask).
- Session-Timeout inserted into DHCP option 51 (IP address lease time).
- Framed-Route that is translated from the standard Cisco Framed-Route format into DHCP option 121 or the DHCP default gateway option (if the network and netmask are appropriate for a default route).
- A copy of relay agent information (option 82). Before the DHCP client receives the packet, the relay removes option 82.
- T1 time set to the Session-Timeout and T2 time set to the Session-Duration.
The client returns a formal request for the offered IP address to the DHCP server in a DHCP REQUEST broadcast message.
The DHCP confirms that the IP address is allocated to the client by returning a DHCP ACK unicast message containing lease information and the DHCP options to the client.
A RADIUS server accounting request starts, followed by a RADIUS server accounting response that is used by the AAA subsystem.
When a RADIUS server attribute is not present in an access-accept message, the corresponding DHCP option is not sent to the DHCP client. If the required information to produce a particular RADIUS server attribute is not available to the DHCP server, the DHCP server does not include information in the RADIUS packet. Non-inclusion can be in the form of not sending an attribute (if there is no information at all), or omitting information from the attribute (in the case of CLI-based format strings).
If a DHCP option is provided to the DHCP server but is invalid, the DHCP server may not transmit the corresponding RADIUS attribute in the access-request, or may transmit an invalid RADIUS server attribute.
DHCP Server and RADIUS Translations
The table below lists the translations of DHCP options in a DHCP DISCOVER message to attributes in a RADIUS server access-request message.
DHCP DISCOVER |
RADIUS Access-Request |
---|---|
Virtual MAC address of the residential gateway |
User-Name |
Not Applicable |
User-Password as configured on the DHCP server |
Gateway address of the relay agent (giaddr field of a DHCP packet) |
NAS-identifier |
Hostname |
Cisco AV pair client-hostname that equals the value of DHCP option 12 |
Vendor class |
Cisco AV pair dhcp-vendor-class that equals a hexadecimal-encoded value of DHCP option 60 |
Client identifier |
Cisco AV pair dhcp-client-id that equals the hexadecimal-encoded value of DHCP option 61 |
DHCP relay information option that can contain VLAN parameter on the D-router |
Cisco AV pair dhcp-relay-info that equals the hexadecimal-encoded value of DHCP option 82 |
The table below lists the translations of attributes in a RADIUS server access-accept message to DHCP options in a DHCP OFFER message.
RADIUS Access-Accept |
DHCP OFFER |
---|---|
Framed-IP-Address |
IP address of the residential gateway |
Framed-IP-Netmask |
Subnet mask (option 1) |
Session-Timeout |
IP address lease time (option 51) |
Cisco AV pair session-duration in seconds, where seconds is greater than or equal to the number of seconds in the Session-Timeout attribute. |
Provides session control on the DHCP server. This attribute is not transmitted to the DHCP client. |
Framed-Route (RADIUS attribute 22). One route for each DHCP option is allowed with a maximum of 16 Framed-Route options for a RADIUS packet. |
Contains up to 16 classless routes in one option (option 121) |
RADIUS Profiles for DHCP Server RADIUS Proxy
When you configure RADIUS server user profiles for DHCP server RADIUS proxy, use the following guidelines:
The Session-Timeout attribute must contain a value, in seconds. If this attribute is not present, the DHCP OFFER is not sent to the client.
A RADIUS user profile must contain the following attributes: - Framed-IP-Address
- Framed-IP-Netmask
- Framed-Route
- Session-Timeout
- Session-Duration--Session-Duration is the Cisco AV pair session-duration = seconds, where seconds is the maximum time for the duration of a lease including all renewals. The value for Session-Duration must be greater than or equal to the Session-Timeout attribute value, and it cannot be zero.
Additional RADIUS server attributes are allowed but are not required. The DHCP server ignores additional attributes that it does not understand. If a RADIUS server user profile contains a required attribute that is empty, the DHCP server does not generate the DHCP options.
How to Configure DHCP Server RADIUS Proxy
- Configuring the DHCP Server for RADIUS-based Authorization
- Monitoring and Maintaining the DHCP Server
Configuring the DHCP Server for RADIUS-based Authorization
Perform this task on the DHCP server to configure address allocation for RADIUS-based authorization of DHCP leases.
1.
enable
2.
configure
terminal
3.
service
dhcp
4. aaa new-model
5.
aaa
group
server
radius
group-name
6.
server
ip-address
[auth-port port-number] [acct-port port-number]
7.
exit
8.
aaa
authorization
network
method-list-name
group
group-name
9.
aaa
accounting
network
method-list-name
start-stop
group
group-name
10.
ip
dhcp
pool
name
11.
accounting
method-list-name
12.
authorization
method
method-list-name
13.
authorization
shared-password
password
14.
authorization
username
string
15. exit
16.
interface
type
slot
/
subslot
/
port
[. subinterface]
17.
encapsulation
dot1q
vlan-id
second-dot1q
{any | vlan-id[, vlan-id[- vlan-id]]}
18.
ip
address
address
mask
19. no shutdown
20.
radius-server
host
ip-address
[auth-port port-number] [acct-port port-number]
21.
radius-server
key
{0 string | 7 string | string}
22.
exit
DETAILED STEPS
Monitoring and Maintaining the DHCP Server
Perform this task to verify and monitor DHCP server information:
1.
enable
2.
debug
ip
dhcp
server
packet
3.
debug
ip
dhcp
server
events
4.
show
ip
dhcp
binding
[address]
5.
show
ip
dhcp
server
statistics
6.
show
ip
dhcp
pool
[name]
7.
show
ip
route
dhcp
[address]
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
|
Step 2 |
debug
ip
dhcp
server
packet
Example: Router# debug ip dhcp server packet |
(Optional) Enables DHCP server debugging. |
Step 3 |
debug
ip
dhcp
server
events
Example:
Router# debug ip dhcp server events
|
(Optional) Reports DHCP server events, such as address assignments and database updates. |
Step 4 |
show
ip
dhcp
binding
[address] Example:
Router# show ip dhcp binding
|
(Optional) Displays a list of all bindings created on a specific DHCP server.
|
Step 5 |
show
ip
dhcp
server
statistics
Example: Router# show ip dhcp server statistics |
(Optional) Displays count information about server statistics and messages sent and received. |
Step 6 |
show
ip
dhcp
pool
[name] Example:
Router# show ip dhcp pool
|
(Optional) Displays the routes added to the routing table by the DHCP server and relay agent. |
Step 7 |
show
ip
route
dhcp
[address] Example:
Router# show ip route dhcp [address]
|
(Optional) Displays information about DHCP address pools. |
Configuration Examples for DHCP Server Radius Proxy
Configuring the DHCP Server Example
The following example shows how to configure a DHCP server for RADIUS-based authorization of DHCP leases. In this example, DHCP clients can attach to Ethernet interface 4/0/1 and Ethernet subinterface 4/0/3.10. The username string (%c-user1) specifies that the RADIUS server sends the Ethernet address of DHCP client named user1 to the DHCP server.
Router> enable Router# configure terminal Router(config)# service dhcp Router(config)# aaa new-model Router(config)# aaa group server radius rad1 Router(config-sg)# server 10.1.1.1 Router(config-sg)# server 10.1.5.10 Router(config-sg)# exit Router(config)# aaa authorization network auth1 group group1 Router(config)# aaa accounting network acct1 start-stop group group1 Router(config)# aaa session-id common Router(config)# ip dhcp database tftp://172.16.1.1/router-dhcp write-delay 100 timeout 5 ! Router(config)# ip dhcp pool pool_common Router(config-dhcp)# accounting acct1 Router(config-dhcp)# authorization method auth1 Router(config-dhcp)# authorization shared-password cisco Router(config-dhcp)# authorization username %c-user1 Router(config-dhcp)# exit ! Router(config)# interface ethernet4/0/1 Router(config-if)# ip address 15.0.0.1 255.255.255.0 Router(config-if)# exit Router(config-if)# interface ethernet4/0/3.10 Router(config-if)# encapsulation dot1q 100 second-dot1q 200 Router(config-if)# ip address 10.1.1.1 255.255.255.0 Router(config-if)# exit Router(config)# radius-server host 10.1.3.2 Router(config)# radius-server key cisco Router(config)# exit
Configuring RADIUS Profiles Example
The following example shows how to configure a typical RADIUS user profile to send attributes in an access-accept message to the DHCP server:
DHCP-00059A3C7800 Password = “metta” Service-Type = Framed, Framed-Ip-Address = 10.3.4.5, Framed-Netmask = 255.255.255.0, Framed-Route = "0.0.0.0 0.0.0.0 10.3.4.1", Session-Timeout = 3600, Cisco:Cisco-Avpair = "session-duration=7200”
Additional References
The following sections provide references related to the DHCP Server RADIUS Proxy feature.
Related Documents
Related Topic |
Document Title |
---|---|
DHCP relay configuration |
Configuring the Cisco IOS XE DHCP Relay Agent |
DHCP commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples |
Cisco IOS IP Addressing Services Command Reference |
Standards
Standards |
Title |
---|---|
No new or modified standards are supported by this functionality. |
-- |
MIBs
MIBs |
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 XE software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
RFCs |
Title |
---|---|
No new or modified RFCs are supported by this feature, and support for existing RFCs was not modified by this feature. |
-- |
Technical Assistance
Description |
Link |
---|---|
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |
Feature Information for DHCP Server RADIUS Proxy
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Configuration Information |
---|---|---|
DHCP Server RADIUS Proxy |
Cisco IOS XE Release 2.4 Cisco IOS XE Release 3.9S |
DHCP Server RADIUS Proxy enables a server to authorize remote clients and allocate addresses based on replies from the server. In Cisco IOS XE 2.4, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers. The following commands were modified by this feature: authorization method (dhcp), authorization shared-password, authorization username (dhcp). |
Glossary
client --A host trying to configure its interface (obtain an IP address) using DHCP or BOOTP protocols.
DHCP --Dynamic Host Configuration Protocol.
giaddr --Gateway IP address. The giaddr field of the DHCP message provides the DHCP server with information about the IP address subnet on which the client is to reside. It also provides the DHCP server with an IP address where the response messages are to be sent.
MPLS --Multiprotocol Label Switching. Emerging industry standard upon which tag switching is based.
relay agent --A router that forwards DHCP and BOOTP messages between a server and a client on different subnets.
server --DHCP or BOOTP server.
VPN --Virtual Private Network. Enables IP traffic to use tunneling to travel securely over a public TCP/IP network.
VRF --VPN routing and forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router. Each VPN instantiated on the PE router has its own VRF.