- Overview of GPRS and UMTS
- Planning to Configure the GGSN
- Configuring GTP Services on the GGSN
- Configuring GGSN GTP Session Redundancy
- Configuring IPv6 PDP Support on the GGSN
- Configuring Enhanced Service-Aware Billing
- Configuring Network Access to the GGSN
- Configuring PPP Support on the GGSN
- Configuring QoS on the GGSN
- Configuring Security on the GGSN
- Configuring Dynamic Addressing on the GGSN
- Configuring Load Balancing on the GGSN
- Monitoring Notifications
- Configuring Charging on the GGSN
Configuring Dynamic Addressing on the GGSN
This chapter describes how to configure dynamic IP addressing on the gateway GRPS support node (GGSN).
Note The tasks in this chapter apply to IPv4 PDP contexts only. For information on IPv6 addressing, see Chapter 4, "Configuring IPv6 PDP Support on the GGSN."
For a complete description of the GGSN commands in this chapter, refer to the Cisco GGSN Command Reference for the Cisco GGSN release you are using. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
This chapter includes the following sections:
•Overview of Dynamic IP Addressing on the GGSN
•Configuring MS Addressing via Local Pools on the GGSN
•Configuring MS Addressing via RADIUS on the GGSN
•Configuring IP Overlapping Address Pools
•Configuring the NBNS and DNS Address for an APN
Overview of Dynamic IP Addressing on the GGSN
There are three methods for configuring the GGSN to assign IP addresses to mobile station users who need to access the public data network (PDN): Dynamic Host Configuration Protocol (DHCP) allocation, Remote Authentication Dial-In User Service (RADIUS) allocation, and local IP address pool allocation configured at the access point name (APN).
A method of dynamic IP addressing can be configured either globally or at the access-point configuration level.
Be sure that the following configuration guidelines are met to support the type of IP address allocation in use on your network:
•DHCP IP address allocation
–Be sure that you configure the scope of the addresses to be allocated on the same subnet as the loopback interface.
–Do not configure an IP address for users on the RADIUS server.
–Specify the peer default ip address dhcp command at the PPP virtual template interface.
–Specify the aaa authorization network method_list none command on the GGSN.
•RADIUS IP address allocation
–Be sure that users are configured on the RADIUS server using the complete username@domain format.
–Specify the no peer default ip address command at the PPP Virtual Template interface.
–For more information about configuring RADIUS services on the GGSN, see the "Configuring Security on the GGSN" chapter in this book.
•Local pool IP address allocation
–Be sure to configure a local pool using the ip local pool command.
–Specify the aaa authorization network method_list none command on the GGSN.
–Specify the peer default ip address pool pool-name command.
Note On the Cisco 7600 platform, dynamic address allocation using the DHCP or RADIUS server methods requires that the DHCP or RADIUS server be Layer 3 routeable from the supervisor engine.
Configuring DHCP on the GGSN
You can use local DHCP services within the Cisco IOS software, or you can configure the GGSN to use an external DHCP server such as the Cisco Network Registrar (CNR). For information about configuring internal DHCP services in the Cisco IOS software, refer to the Cisco IOS Configuration Fundamentals Configuration Guide.
The DHCP server can be specified in two ways:
•At the global configuration level, using the gprs default dhcp-server command
•At the access-point configuration level, using the dhcp-server command
To configure DHCP support on the GGSN, you must configure either the gprs default ip-address-pool global configuration command or the ip-address-pool access-point configuration command with the dhcp-proxy-client keyword option.
After you configure the access point for DHCP proxy client services, use the dhcp-server access-point configuration command to specify a DHCP server.
Use the ip-address argument to specify the IP address of the DHCP server. The second, optional ip-address argument can be used to specify the IP address of a backup DHCP server to be used in the event that the primary DHCP server is unavailable. If you do not specify a backup DHCP server, then no backup DHCP server is available.
If you specify a DHCP server at the access-point level by using the dhcp-server command, then the server address specified at the access point overrides the address specified at the global level. If you do not specify a DHCP server address at the access-point level, then the address specified at the global level is used.
Therefore, you can have a global address setting and also one or more local access-point level settings if you need to use different DHCP servers for different access points.
Use the vrf keyword when the DHCP server itself is located within the address space of a VRF interface on the GGSN. If the DHCP server is located within the VRF address space, then the corresponding loopback interface for the dhcp-gateway-address must also be configured within the VRF address space.
This section contains the following information:
•Configuring DHCP Server Communication Globally
•Configuring DHCP at the GGSN Global Configuration Level
•Configuring a Local DHCP Server
Configuring DHCP Server Communication Globally
This section describes how to configure a global DHCP server host that the GGSN can use to assign IP addresses to mobile users. You can configure additional DHCP server communication at the GGSN global configuration level.
To globally configure DHCP server communication on the router or instance of Cisco IOS software, use the following commands, beginning in global configuration mode:
For more information about configuring global DHCP services, refer to the Cisco IOS IP Configuration Guide, Cisco IOS IP Command References, and the Cisco IOS Dial Technologies Command Reference publications.
Configuring DHCP at the GGSN Global Configuration Level
To complete the DHCP configuration for the GGSN, you can configure DHCP at the GGSN global configuration level. When you configure DHCP at the GGSN configuration level, you can configure DHCP server communication for all access points or for a specific access point.
Configuring DHCP at the GGSN configuration level includes the following tasks:
•Configuring a Loopback Interface (Required)
•Specifying a DHCP Server for All Access Points (Optional)
•Specifying a DHCP Server for a Particular Access Point (Optional)
Configuring a Loopback Interface
When you configure a DHCP gateway address for DHCP services at an access point, and when you are supporting unique supernets across all access points on the GGSN for DHCP, then you must configure a loopback interface for each unique network.
A loopback interface is a software-only interface that emulates an interface that is always up. It is a virtual interface supported on all platforms. The interface number is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces you can create.
To configure a loopback interface on the GGSN, use the following commands, beginning in global configuration mode:
Specifying a DHCP Server for All Access Points
When processing DHCP address allocation, the GGSN software first checks to see whether a DHCP server has been specified at the access-point configuration level. If a server has been specified, the GGSN uses the DHCP server specified at the access point. If no DHCP server is specified at the access-point configuration level, then the GGSN uses the default GGSN DHCP server.
To specify a DHCP server for all GGSN access points, use the following commands, beginning in global configuration mode:
Specifying a DHCP Server for a Particular Access Point
To override the default DHCP server configured for all access points, you can specify a different DHCP server for a particular access point. Or, if you choose not to configure a default GGSN DHCP server, you can specify a DHCP server at each access point.
To specify a DHCP server for a particular access point, use the following commands, beginning in access-point configuration mode:
Configuring a Local DHCP Server
Note We do not recommend using a local DHCP server on the Cisco 7600 platform.
Although most networks use external DHCP servers, such as that available through the Cisco Network Registrar (CNR), you can also configure internal DHCP services on the GGSN. If you use local DHCP services on the GGSN, then there are a couple of commands that you should configure to improve the internal DHCP response times.
To optimize local DHCP services on the GGSN, use the following commands, beginning in global configuration mode:
Configuration Example
The following example shows a VRF configuration for vpn3 (without tunneling) using the ip vrf global configuration command. Because the ip vrf command establishes both VRF and CEF routing tables, notice that ip cef also is configured at the global configuration level to enable CEF switching at all of the interfaces.
The following other configuration elements must also associate the same VRF named vpn3:
•FastEthernet0/0 is configured as the Gi interface using the ip vrf forwarding interface configuration command.
•Access-point 2 implements VRF using the vrf command access-point configuration command.
The DHCP server at access-point 2 also is configured to support VRF. Notice that access-point 1 uses the same DHCP server, but is not supporting the VRF address space. The IP addresses for access-point 1 will apply to the global routing table:
aaa new-model
!
aaa group server radius foo
server 10.2.3.4
server 10.6.7.8
!
aaa authentication ppp foo group foo
aaa authorization network foo group foo
aaa accounting network foo start-stop group foo
!
ip cef
!
ip vrf vpn3
rd 300:3
!
interface Loopback1
ip address 10.30.30.30 255.255.255.255
!
interface Loopback2
ip vrf forwarding vpn3
ip address 10.27.27.27 255.255.255.255
!
interface FastEthernet0/0
ip vrf forwarding vpn3
ip address 10.50.0.1 255.255.0.0
duplex half
!
interface FastEthernet1/0
ip address 10.70.0.1 255.255.0.0
duplex half
!
interface loopback 1
ip address 10.8.0.1 255.255.255.0
!
interface Virtual-Template1
ip unnumber loopback 1
encapsulation gtp
gprs access-point-list gprs
!
ip route 10.10.0.1 255.255.255.255 Virtual-Template1
ip route vrf vpn3 10.100.0.5 255.255.255.0 fa0/0 10.50.0.2
ip route 10.200.0.5 255.255.255.0 fa1/0 10.70.0.2
!
no ip http server
!
gprs access-point-list gprs
access-point 1
access-point-name gprs.pdn.com
ip-address-pool dhcp-proxy-client
dhcp-server 10.200.0.5
dhcp-gateway-address 10.30.30.30
network-request-activation
exit
!
access-point 2
access-point-name gprs.pdn2.com
access-mode non-transparent
ip-address-pool dhcp-proxy-client
dhcp-server 10.100.0.5 10.100.0.6 vrf
dhcp-gateway-address 10.27.27.27
aaa-group authentication foo
vrf vpn3
exit
!
gprs default ip-address-pool dhcp-proxy-client
gprs gtp ip udp ignore checksum
!
radius-server host 10.2.3.4 auth-port 1645 acct-port 1646 non-standard
radius-server host 10.6.7.8 auth-port 1645 acct-port 1646 non-standard
radius-server key ggsntel
Configuring MS Addressing via Local Pools on the GGSN
As the number of PDP contexts increases, allocating IP addresses via locally-configured address pools improves the PDP context activation rate. Whether or not addresses are allocated to MSs using local pools is specified at the access-point configuration level and requires that a local pool or pools of IP address have been configured on the GGSN using the ip local pool configuration command.
Hold Back Timer
The IP local pool hold back timer feature (recycle delay keyword option) enables you to configure a specific amount of time a newy-released IP address is held before being made available for reassignment. This ensures that an IP address recently released when a PDP session was deleted is not re-assigned to another PDP context before the IP-to-user relationship has been deleted from all back-end components of the system. If an IP address is reassgined to a new PDP context immediately, the back-end system could incorrectly associate the new user with the record of the previous user, and therefore associate the charging and service access of the new user to the previous user.
The hold back functionality is provided by the support of a new timestamp field added to the pool element data structure. When a request to allocate a specific address is made, if the address is available for reassignment, the current time is checked agains the timestamp field of the element. If that number is equal to, or exceeds the number of seconds configured for the recycle delay, the address is reassigned.
When a request is made to allocate the first free address from the free queue, the difference between the current timesteamp and the timestamp stored for the element is calculated. If the number is equal to, or exceeds, the configured recycle delay, the address is allocated. If the number is not equal to, or does not exceed the configured recycle delay, the address is not allocated for that request. (The free queue is a first-in first-out [FIFO] queue. Therefore, all other elements will have a great recycle delay than the first element.)
When an address assignment is blocked because an IP address is held for some time, a count of blocked address assignments that is maintained for the local pool is incremented.
Note In Cisco GGSN Release 7.0, the hold back timer feature does not support IPv6 local pools.
To configure a local IP address pool, use the following command in global configuration mode:
To assign a local pool to an access-point, use the following command in access-point configuration mode:
|
|
|
---|---|---|
Step 1 |
Router(config-access-point)# ip-address-pool local pool-name |
(Optional) Specifies that a local pool provides the IP address. |
Note Using VRF at the access point, you can configure APNs that use the same IP address pool (overlapping addresses). If using a Supervisor II, you must tunnel the encapsulated VRF traffic through the Supervisor using a GRE tunnel.
Fore more information on configuring VPN access via VRF from an access point, see the "VPN Access Using VRF Configuration Task Lists" section on page 7-13.
The Cisco 7600 Sup720 supports VRF.
To verify the local pool configure, use the show ip local [pool name] command in privileged EXEC mode:
Router#show ip local pool
Pool Begin End Free In use Blocked
poola 10.8.8.1 10.8.8.5 5 0 0
Router #show ip local pool poolA
Pool Begin End Free In use Blocked
poola 10.8.8.1 10.8.8.5 5 0 0
Available addresses:
10.8.8.1
10.8.8.2
10.8.8.3
10.8.8.4
10.8.8.5
Inuse addresses:
None
Held addresses: Time Remaining
None
Configuration Example
The following is a configuration example of a local address pool configured at the APN.
!
ip local pool local_pool1 128.1.0.1 128.1.255.254
!
access-point 1
access-point-name gprs.pdn.com
ip-address-pool local local_pool1
aggregate 128.1.0.0/16
exit
Configuring MS Addressing via RADIUS on the GGSN
Dynamic IP addressing via a RADIUS server is configured at the access-point configuration level using the ip-address-pool access-point configuration command.
For more information about the ip-address-pool access-point configuration command, see "Configuring Additional Real Access Point Options" section on page 7-20. For more information about configuring RADIUS, see the Cisco IOS Security Configuration Guide.
Configuring IP Overlapping Address Pools
The IP Overlapping Address Pools feature improves flexibility in assigning IP addresses dynamically. This feature allows you to configure overlapping IP address pool groups to create different address spaces and concurrently use the same IP addresses in different address spaces.
IP Overlapping Address Pools gives greater flexibility in assigning IP addresses dynamically. It allows you to configure overlapping IP address pool groups to create different address spaces and concurrently use the same IP addresses in different address spaces.
With Cisco IOS Release 12.3(2)XB and later, the GGSN supports the concept of an IP address group to support multiple IP address spaces and still allow the verification of nonoverlapping IP address pools within a pool group. Pool names must be unique within the GGSN. The pool name carries an implicit group identifier because that pool name can be associated only with one group. Pools without an explicit group name are considered members of the base system group and are processed in the same manner as the original IP pool implementation.
Existing configurations are not affected by the new pool feature. The "group" concept is an extension of the existing ip local pool command. Processing of pools that are not specified as a member of a group is unchanged from the existing implementation.
To configure a local IP address pool group and verify that it exists, use the following commands in global configuration mode:
Configuration Examples
The following are configuration examples for configuring IP overlapping address pools.
•Defining Local Address Pooling as the Global Default
•Configuring Multiple Ranges of IP Addresses into One Pool Example
Defining Local Address Pooling as the Global Default
The following example shows how to configure local pooling as the global default mechanism:
ip address-pool local ip local pool default 192.169.15.15 192.68.15.16
Configuring Multiple Ranges of IP Addresses into One Pool Example
The following example shows how to configure two ranges of IP addresses for one IP address pool:
ip local pool default 192.169.10.10 192.169.10.20
ip local pool default 192.169.50.25 192.169.50.50
Configuring IP Overlapping Address Pools on a GGSN on the Cisco 7600 Platform with Supervisor II / MSFC2 Example
The following example shows how to configure IP overlapping address pools on the Cisco 7600 platform
The following examples also show a partial configuration for two VPNs (vpn1 and vpn2) and their associated GRE tunnel configurations (Tunnel1 and Tunnel2).
On the GGSN:
service gprs ggsn
!
hostname 7600-7-2
!
ip cef
!
ip vrf vpn1
description GRE Tunnel 1
rd 100:1
!
ip vrf vpn2
description GRE Tunnel 3
rd 101:1
!
interface Loopback1
ip address 150.1.1.72 255.255.0.0
!
interface Loopback100
description GPRS GTP V-TEMPLATE IP ADDRESS
ip address 9.9.9.72 255.255.255.0
!
interface Tunnel1
description VRF-GRE to PDN 7500(13) Fa0/1
ip vrf forwarding vpn1
ip address 50.50.52.72 255.255.255.0
tunnel source 150.1.1.72
tunnel destination 165.2.1.13
!
interface Tunnel2
description VRF-GRE to PDN PDN x(12) Fa3/0
ip vrf forwarding vpn2
ip address 80.80.82.72 255.255.255.0
tunnel source 150.1.1.72
tunnel destination 167.2.1.12
!
interface GigabitEthernet0/0.1
description Gi
encapsulation dot1Q 100
ip address 10.1.2.72 255.255.255.0
!
interface Virtual-Template1
description GTP v-access
ip unnumbered Loopback100
encapsulation gtp
gprs access-point-list gprs
!
router ospf 10
network 10.1.2.0 0.0.0.255 area 10
network 150.1.0.0 0.0.255.255 area 10
!
ip local pool vpn1_pool 100.2.0.1 100.2.255.255 group vpn1
ip local pool vpn2_pool 100.2.0.1 100.2.255.255 group vpn2
ip route vrf vpn1 0.0.0.0 255.255.255.0 Tunnel1
ip route vrf vpn2 0.0.0.0 255.255.255.0 Tunnel2
gprs access-point-list gprs
access-point 1
access-point-name apn.vrf1.com
access-mode non-transparent
aaa-group authentication ipdbfms
ip-address-pool local vpn1_pool
vrf vpn1
!
access-point 2
access-point-name apn.vrf2.com
access-mode non-transparent
aaa-group authentication ipdbfms
ip-address-pool local vpn2_pool
vrf vpn2
!
Related configuration on the Supervisor / MSFC2:
interface FastEthernet9/5
no ip address
switchport
switchport access vlan 167
no cdp enable
!
interface FastEthernet9/10
no ip address
switchport
switchport access vlan 165
no cdp enable
!
interface Vlan165
ip address 165.1.1.1 255.255.0.0
!
interface Vlan167
ip address 167.1.1.1 255.255.0.0
!
! provides route to tunnel endpoints on GGSNs
router ospf 10
network 10.1.2.0 0.0.0.255 area 10
!
! routes to tunnel endpoints on PDN
!
ip route 165.2.0.0 255.255.0.0 165.1.1.13
ip route 167.2.0.0 255.255.0.0 167.1.1.12
Configuring the NBNS and DNS Address for an APN
You can configure a primary and secondary NetBIOS Name Service (NBNS) and domain name system (DNS) under an APN. This feature is benefits address allocation schemes where there is no mechanism to obtain these address. Also, for a RADIUS-based allocation scheme, it prevents the operator from having to configure a NBNS and DNS under each user profile.
The NBNS and DNS addresses can come from three possible sources: DHCP server, RADIUS server, or local APN configuration. The criterium for selecting the addresses depends on the IP address allocation scheme configured under the APN. Depending on the configuration, the criterium for selecting the DNS and NBNS addresses is as follows:
1. DHCP-based IP address allocation scheme (local and external)—NBNS address returned from the DHCP server is sent to the MS. If the DHCP server does not return an NBNS address, the local APN configuration is used.
2. RADIUS-based IP address allocation scheme—NBNS address returned from the RADIUS server (in Access-Accept responses) is used. If the RADIUS server does not return an NBNS address, the local APN configuration is used.
3. Local IP Address Pool-based IP address allocation scheme—Local APN configuration is used.
4. Static IP Addresses—Local APN configuration is used.
Note The GGSN sends NBNS and DNS addresses in the create PDP response only if the MS is requesting the DNS address in the PCO IE.
To specify a primary (and backup) NBNS to be sent in create PDP responses at the access point, use the nbns primary access-point configuration command. To remove the NBNS from the access-point configuration, use the no form of this command
nbns primary ip-address [secondary ip-address]
To specify a primary (and backup) DNS to be sent in create PDP responses at the access point, use the dns primary access-point configuration command. To remove the DNS from the access-point configuration, use the no form of this command
dns primary ip-address [secondary ip-address]