The figure below shows a sample IOS SLB firewall load-balancing network with the following components:

• Two firewalls with IP addresses as shown
• An internal firewall load-balancing device on the secure side of the firewalls
• An external firewall load-balancing device on the Internet side of the firewalls
• One firewall farm named FIRE1, containing both firewalls

Figure 2. IOS SLB with Layer 3 Firewalls in Different Subnets

When you configure IOS SLB firewall load balancing, the load-balancing devices use route lookup to recognize flows destined for the firewalls. To enable route lookup, you must configure each device with the IP address of each firewall that will route flows to that device.

In the following firewall farm configuration samples:

• The internal (secure side) firewall load-balancing device is configured with firewall IP addresses 10.1.3.1 and 10.1.4.1.
• The external (Internet side) firewall load-balancing device is configured with firewall IP addresses 10.1.1.2 and 10.1.2.2.

The figure below shows a sample IOS SLB load-balancing network with server load balancing and firewall load balancing running together, and the following components:

• Two real servers with IP addresses as shown
• One server farm named PUBLIC, containing both real servers
• Two firewalls with IP addresses as shown
• One firewall farm named FIRE1, containing both firewalls
• An internal IOS SLB device on the secure side of the firewalls, performing server load balancing and firewall load balancing
• An external firewall load-balancing device on the Internet side of the firewalls

Figure 3. IOS SLB with Server Load Balancing and Firewall Load Balancing

In the following firewall farm configuration samples:

• The internal (secure side) firewall load-balancing device is configured with firewall IP addresses 10.1.3.1 and 10.1.4.1.
• The external (Internet side) firewall load-balancing device is configured with firewall IP addresses 10.1.1.2 and 10.1.2.2.

The figure below shows a sample IOS SLB load-balancing network with multiple firewall farms and the following components:

• Four firewalls with IP addresses as shown
• An internal firewall load-balancing device on the secure side of the firewalls
• An external firewall load-balancing device on the Internet side of the firewalls
• One firewall farm named ABCFARM, containing the two firewalls on the left.
• One firewall farm named XYZFARM, containing the two firewalls on the right.

Figure 4. IOS SLB with Multiple Firewall Farms

In the following firewall farm configuration samples:

• The internal (secure side) firewall load-balancing device is configured with firewall IP addresses 10.1.3.1 and 10.1.4.1.
• The external (Internet side) firewall load-balancing device is configured with firewall IP addresses 10.1.1.2 and 10.1.2.2.

The figure below illustrates a basic dual firewall load balancing “sandwich” configuration hosted on one IOS SLB device, including Virtual Private Network (VPN) routing and forwarding (VRF) and access interface configuration. VL105, VL106, VL107, and VL108 are VLANs.

Note	The client and server in this configuration are directly connected; in a more typical deployment, additional routes would be needed inside and outside the VRF.

Figure 5. IOS SLB with Dual Firewall Load Balancing “Sandwich”

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip vrf client
 rd 0:1
!
ip slb probe P642 ping
 address 10.10.106.42
 interval 120
ip slb probe P643 ping
 address 10.10.106.43
 interval 120
ip slb probe P742 ping
 address 10.10.107.42
 interval 120
ip slb probe P743 ping
 address 10.10.107.43
 interval 120
!
ip slb firewallfarm CLIENT
 access inbound Vlan105
 access outbound Vlan106
 no inservice
!
 real 10.10.106.42
  probe P642
  inservice
 real 10.10.106.43
  probe P643
  inservice
 protocol tcp
  sticky 180 source
 protocol datagram
  sticky 180 source
 predictor hash address port
!
ip slb firewallfarm SERVER
 access inbound Vlan108
 access outbound Vlan107
 inservice
!
 real 10.10.107.42
  probe P742
  inservice
 real 10.10.107.43
  probe P743
  inservice
 protocol tcp
  sticky 180 destination
 protocol datagram
  sticky 180 destination
 predictor hash address port
!
mls flow ip interface-full
!
!*************************************************
!* Switchports, port channels and trunks         *
!* added to vlans 105-108 (left out for brevity) *
!*************************************************
!
interface Vlan105
 ip vrf forwarding client
 ip address 10.10.105.2 255.255.255.0
!
interface Vlan106
 ip vrf forwarding client
 ip address 10.10.106.2 255.255.255.0
!
interface Vlan107
 ip address 10.10.107.2 255.255.255.0
!
interface Vlan108
 ip address 10.10.108.2 255.255.255.0
!
ip route 10.10.105.0 255.255.255.0 10.10.107.42
ip route vrf client 10.10.108.0 255.255.255.0 10.10.106.42

The figure below shows a sample configuration with IOS SLB real server connections configured as part of a server farm, focusing on using ping and HTTP probes to monitor applications that are server load-balanced.

Figure 6. Sample Ping and HTTP Probe Topology

The topology shown in the figure above is a heterogeneous server farm servicing one virtual server. Following are the configuration statements for this topology, including a ping probe named PROBE1 and an HTTP probe named PROBE2:

! Configure ping probe PROBE1, change CLI to IOS SLB probe configuration mode
ip slb probe PROBE1 ping
! Configure probe to receive responses from IP address 13.13.13.13
  address 13.13.13.13
! Configure unacknowledged ping threshold to 16
  faildetect 16
! Configure ping probe timer interval to send every 11 seconds
  interval 11
! Configure HTTP probe PROBE2
  ip slb probe PROBE2 http
! Configure request method as POST, set URL as /probe.cgi?all
  request method post url /probe.cgi?all
! Configure header HeaderName
  header HeaderName HeaderValue
! Configure basic authentication username and password
  credentials Semisweet chips
! Exit to global configuration mode
  exit
! Enter server farm configuration mode for server farm PUBLIC
ip slb serverfarm PUBLIC
! Configure NAT server and real servers on the server farm
  nat server
  real 10.1.1.1
   inservice
  real 10.1.1.2
   inservice
  real 10.1.1.3
   inservice
  real 10.1.1.4
   inservice
  real 10.1.1.5
   inservice
! Configure ping probe on the server farm
  probe PROBE1
! Configure HTTP probe on the server farm
  probe PROBE2
  end

The figure below shows a typical datacenter and IOS SLB configuration. Virtual server ACME_VSERVER is configured with two real servers (10.10.10.1 and 10.10.10.2) in server farm ACME_FARM. The user wants the real servers to fail based on the health of the backend server (10.10.10.3). To accomplish this configuration without sending health checks through the real servers, the user defines BACKEND, a routed ping probe to the backend server’s IP address.

Figure 7. IOS SLB with a Routed Ping Probe

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb probe BACKEND ping
  address 10.10.10.3 routed
ip slb serverfarm ACME_SFARM
  nat server
  probe BACKEND
  real 10.10.10.1
   inservice
  real 10.10.10.2
   inservice
ip slb vserver ACME_VSERVER
  virtual 10.10.10.10 tcp 80
  serverfarm ACME_SFARM
  inservice	

The figure below shows a sample configuration with IOS SLB real server connections configured as part of a server farm, focusing on the configuration of the NAT server and address pool of clients.

Figure 9. Sample IOS SLB NAT Topology

The topology in the figure above has four web servers, configured as follows:

• Servers 1, 2, and 3 are running single HTTP server applications listening on port 80.
• Server 4 has multiple HTTP server applications listening on ports 8080, 8081, and 8082.

Server 1 and Server 2 are load-balanced using Switch A, which is performing server address translation.

Server 3 and Server 4 are load-balanced using Switch B and Switch C. These two switches are performing both server and client address translation since there are multiple paths between the clients and the servers. These switches also must perform server port translation for HTTP packets to and from Server 4.

The following example shows configuration statements for the following items:

• A DNS probe, PROBE4, configured to supply real server IP address 13.13.13.13 in response to domain name resolve requests.
• A server farm, DNS, that is configured to use server NAT and PROBE4.
• An all-port virtual server, 10.11.11.11, associated with server farm DNS, that performs per-packet server load balancing for UDP connections.
• A real server, 10.1.1.3, associated with server farm DNS, configured for static NAT and per-packet server load balancing.

ip slb probe PROBE4 dns
 lookup 13.13.13.13
!
ip slb serverfarm DNS
 nat server
 probe PROBE4
 real 10.1.1.3
  inservice
!
ip slb vserver DNS
 virtual 10.11.11.11 UDP 0 service per-packet
 serverfarm DNS
!
ip slb static nat 10.11.11.11 per-packet
 real 10.1.1.3

There are several different ways in which you can configure IOS SLB stateless backup. The differences between the configurations depend on the networking capabilities of your load balancing devices, and on the capabilities of the distribution devices that direct client traffic to those load balancing devices.

• If a load balancing device is not capable of both Layer 2 switching and VLAN trunking, you must connect it and its real servers to a Layer 2 switch. This configuration is required in order to use HSRP on the server-side VLANs.
• If a distribution device is capable of Layer 3 switching, it can use route redistribution to direct flows to the active load balancing device.
• If a distribution device is capable of Layer 2 switching, it can use client-side HSRP on the load balancing device to direct flows to the active load balancing device.
• While HSRP offers faster failover times, routing converges quickly enough for most configurations. If you use both client-side and server-side HSRP on the load balancing devices, you must use HSRP interface tracking and priorities to synchronize the client-side and server-side HSRP groups.

This section contains the following examples, illustrating several different IOS SLB stateless backup configurations:

Note	Stateful backup is omitted from these examples in the interest of simplicity. To see an example that uses stateful backup, see the “Example: How to Configure IOS SLB with Stateful Backup” section.

This sample configuration focuses on the IOS SLB real server connections configured as part of a server farm, with real and virtual servers over Fast Ethernet interfaces configured with stateful backup standby connections.

The figure below is an example of a stateful backup configuration, using HSRP on both the client and server sides to manage failover. The real servers route outbound flows to 10.10.3.100, which is the HSRP address on the server side interfaces. The client (or access router), routes to the virtual IP address (10.10.10.12) through 10.10.2.100, HSRP address on the client side.

Notice the loopback interfaces configured on both devices for the exchange of these messages. Each IOS SLB should also be given duplicate routes to the other switch loopback address. This configuration allows replication messages to flow despite an interface failure.

Note	To allow HSRP to function properly, the set spantree portfast command must be configured on any Layer 2 device between the IOS SLB switches.

Figure 14. IOS SLB Stateful Environment

In the figure below, the IOS SLB device includes two Supervisor engines configured for stateful backup. If the active Supervisor engine fails, the backup Supervisor engine takes over through RPR+ with IOS SLB synchronization information already populated. IOS SLB replicates state information for virtual server ACME_VSERVER (10.10.10.10) from the active Supervisor engine to the backup every 20 seconds. The real servers (10.10.10.1, 10.10.10.2, and 10.10.10.3) are configured in server farm ACME_SFARM.

Figure 15. IOS SLB with Redundant Route Processors

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb replicate slave rate 300
ip slb serverfarm ACME_SFARM
  nat server
  real 10.10.10.1
   inservice
  real 10.10.10.2
   inservice
  real 10.10.10.3
   inservice
ip slb vserver ACME_VSERVER
 virtual 10.10.10.10 tcp 80
 replicate interval 20
 replicate slave
 serverfarm ACME_SFARM
 inservice

The figure below shows an IOS SLB network configured for active standby, with two IOS SLB devices load-balancing the same virtual IP address while backing up each other. If either device fails, the other takes over its load through normal HSRP failover and IOS SLB stateless redundancy.

Figure 16. IOS SLB Active Standby

The sample network configuration in the figure above has the following characteristics:

• SLB 1 balances servers 1A and 1B and SLB 2 balances 2A and 2B.
• One virtual IP address (10.10.10.12 for web) is supported across the two IOS SLB devices.
• Client traffic is divided in an access router, sending clients with even IP addresses to HSRP1 (10.10.5.100) and clients with odd IP addresses to HSRP2 (10.10.2.100). SLB 1 is configured as primary for clients with odd IP addresses, and SLB 2 is primary for clients with even IP addresses.
• The IOS SLB devices balance the traffic to disjoint sets of real servers. (If client NAT was used in this example, this characteristic would not be a requirement).
• Each set of real servers has a default gateway configured to its IOS SLB device.
• The HSRP address on VLAN 105 is 10.10.5.100. The HSRP address on VLAN 102 is 10.10.2.100.

The following example shows the configuration for the IOS SLB device shown in the figure above, which balances WAP flows on UDP port 9201 (WSP/WTP/UDP):

ip slb probe PROBE3 wsp
  url http://localhost/test.txt
!
ip slb serverfarm WAPFARM
  nat server
  real 10.10.2.1
  inservice
  real 10.10.2.2
  inservice
  real 10.10.2.3
  inservice
  probe PROBE3
!
ip slb vserver VSERVER
  virtual 10.10.1.1 udp 9201
  serverfarm WAPFARM
  idle 3000
  inservice

The following example shows the configuration for the IOS SLB device shown in the figure above, which balances WAP flows on UDP port 9203 (WSP/WTP/WTLS/UDP):

ip slb probe PROBE1 ping
!
ip slb serverfarm WAPFARM
  nat server
  real 10.10.2.1
  inservice
  real 10.10.2.2
  inservice
  real 10.10.2.3
  inservice
  probe PROBE1
!
ip slb vserver VSERVER
  virtual 10.10.1.1 udp 9203
  serverfarm WAPFARM
  idle 3000
  inservice

The figure below shows an IOS SLB network configured with route health injection with the following characteristics:

• Both IOS SLB devices are configured with the same virtual IP address.
• Each IOS SLB device has a server farm containing only the locally attached web server as a real server.
• The path to SLB A has the lower weight.

Figure 19. Two Distributed Sites with One Web Server Each

When both web servers in the figure above are operational, the client router receives the host route from both IOS SLB devices.

If Web Server A fails, the virtual server for the virtual IP address on SLB A enters FAILED state and stops advertising the host route for the virtual IP address. The client router then begins using the route to SLB B.

When Web Server A is again available, the virtual server again advertises the host route for the virtual IP address, and the client router begins using SLB A.

The figure below shows an IOS SLB network configured with route health injection with the following characteristics:

• Both IOS SLB devices are configured with the same virtual IP address.
• Each IOS SLB device has a server farm containing two locally attached web servers as real servers.
• The path to SLB A has the lower weight.

Figure 20. Two Distributed Sites with Two Web Servers Each

When all web servers in the figure above are operational, the client router receives the host route from both IOS SLB devices.

If one web server in either server farm fails, the route continues to be advertised by the given IOS SLB device.

If both Web Server A1 and Web Server A2 fail, the virtual server for the virtual IP address on SLB A enters FAILED state and stops advertising the host route for the virtual IP address. The client router then begins using the route to SLB B.

When either Web Server A1 or Web Server A2 is again available, the virtual server again advertises the host route for the virtual IP address, and the client router begins using SLB A.

The figure below shows an IOS SLB network configured with route health injection with the following characteristics:

• Both IOS SLB devices are configured with the same virtual IP address.
• Each IOS SLB device has a server farm containing only the locally attached web server as a real server.
• Each site has a primary IOS SLB device and a backup IOS SLB device.
• The path to SLB A has the lower weight.

Figure 21. Two Distributed Sites with One Web Server and a Backup IOS SLB Switch Each

When both web servers in the figure above are operational, the client router receives the host route from both SLB A Primary and SLB B Primary.

If SLB A Primary fails, SLB A Backup begins advertising the host route to the virtual IP address. If SLB A Backup also fails, the virtual server for the virtual IP address on SLB A Primary and SLB A Backup enters FAILED state and stops advertising the host route for the virtual IP address. The client router then begins using the route to SLB B Primary (or to SLB B Backup, if SLB B Primary is not available).

When either SLB A Primary or SLB A Backup is again available, the virtual server again advertises the host route for the virtual IP address, and the client router begins using SLB A Primary or SLB A Backup.

The figure below shows a typical GPRS load-balancing configuration without GTP cause code inspection enabled. In this configuration:

• IOS SLB can balance GPRS flows across multiple real GGSNs. The SGSN “sees” the real GGSNs as one virtual GGSN. This configuration increases the flow-handling capability of the real GGSNs and increases the reliability and availability.
• The virtual template address of the SGSN is 10.111.111.111.
• The virtual template address of GGSN1 is 192.168.1.1.
• The virtual template address of GGSN2 is 192.168.2.2.
• The virtual template address of GGSN3 is 192.168.3.3.

Figure 22. IOS SLB with GPRS Load Balancing

Following are the configuration statements for the configuration shown in the figure above:

For more detailed GGSN configuration examples, refer to the Cisco IOS Mobile Wireless Configuration Guide .

The following example uses the same basic configuration as in the “Example: How to Configure IOS SLB with GPRS Load Balancing Without GTP Cause Code Inspection", including the network shown in the figure above, but with the addition of NAT:

For more detailed GGSN configuration examples, refer to the Cisco IOS Mobile Wireless Configuration Guide.

The following example uses the same basic configuration as in the “Example: How to Configure IOS SLB with GPRS Load Balancing and NAT” section, including the network shown in the figure above, but with the GTP cause code inspection enabled. In this configuration:

• The GSN idle timer is set to 20 seconds.
• The GTP request idle timer is set to 15 seconds.
• The virtual server accepts PDP context creates only from International Mobile Subscriber IDs (IMSIs) with carrier code mcc 222 mnc 22.

Following are the configuration statements for the configuration shown in the figure above, with the addition of NAT and GTP cause code inspection support:

For more detailed GGSN configuration examples, refer to the Cisco IOS Mobile Wireless Configuration Guide .

The following sample configuration enables IOS SLB to support multiple server farms behind a GPRS load balancing virtual server, using access point names (APNs) to select server farms. Server farm farm6 is configured without an associated map, and therefore acts as a default server farm. If IOS SLB cannot match any of the other server farm maps, and a default server farm is configured, IOS SLB sends the GPRS request to the default serverfarm.

ip slb map 1 gtp
 apn cisco*
ip slb map 4 gtp
 apn abc.microsoft.com
 apn xyz.intel.com
ip slb map 5 gtp
 apn yahoo.com
!
ip slb serverfarm farm1
 real 10.0.0.1
 inservice
 real 10.0.0.2
 inservice
ip slb serverfarm farm2
 real 10.0.0.3
 inservice
 real 10.0.0.4
 inservice
ip slb serverfarm farm3
 real 10.0.0.5
 inservice
 real 10.0.0.6
 inservice
ip slb serverfarm farm4
 real 10.0.0.7
 inservice
 real 10.0.0.8
 inservice
ip slb serverfarm farm5
 real 10.0.0.9
 inservice
 real 10.0.0.10
 inservice
ip slb serverfarm farm6
 real 10.0.0.11
 inservice
!
ip slb map 1 gtp
 apn cisco*
ip slb map 4 gtp
 apn abc.microsoft.com
 apn xyz.intel.com
ip slb map 5 gtp
 apn yahoo.com
!
ip slb vserver GGSN_SERVER
 virtual 10.10.10.10 udp 0 service gtp
 serverfarm farm1 backup farm2 map 1 priority 3
 serverfarm farm4 map 4 priority 1
 serverfarm farm5 map 5 priority 4
 serverfarm farm6
 inservice

The following sample configuration enables IOS SLB to support dual-stack addresses for GTP load balancing.

ip slb serverfarm SF1
 real 172.16.88.5 
  weight 1
  inservice
!
ip slb serverfarm SF2
 real 172.16.88.6 
  weight 1
  inservice
!
ip slb serverfarm SF3
 real 172.16.88.7 ipv6 2342:2342:2343:FF04:2388:BB03:3329:8612 
  weight 1
  inservice
!
ip slb serverfarm SF4
 real 172.16.88.8 ipv6 2342:2342:2343:FF04:2388:BB03:3423:8912 
  weight 1
  inservice
!
ip slb vserver VS2
 virtual 4.3.2.1 ipv6 2342:2342:2343:FF04:2341:AA03:2323:8912 udp 0 service gtp
 serverfarm sf1 backup sf2 ipv6-primary sf3 ipv6-backup sf4
 idle gtp request 90
 idle gtp imsi 10000000
 sticky gtp imsi group 1
 gtp notification cac 3
 inservice

The figure below shows a typical IOS SLB RADIUS load-balancing configuration for a GPRS network. In this configuration:

• RADIUS requests are load-balanced between SSG RADIUS proxy servers 10.10.10.1 and 10.10.10.2.
• End-user data packets are routed to the IOS SLB device.
• End-user data packets from the 1.1.1.0 subnet are directed by IOS SLB to SSG1.
• End-user data packets from the 1.1.2.0 subnet are directed by IOS SLB to SSG2.

Figure 24. IOS SLB with RADIUS Load Balancing for a GPRS Network

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb route 1.1.0.0 255.255.0.0 framed-ip
!
ip slb serverfarm SSGFARM
 nat server
 real 10.10.10.1
  inservice
 real 10.10.10.2
  inservice
!
ip slb vserver RADIUS_ACCT
 virtual 10.10.10.10 udp 1813 service radius
 serverfarm SSGFARM
 idle radius request 20
 idle radius framed-ip 7200
 sticky radius framed-ip group 1
 inservice
!
ip slb vserver RADIUS_AUTH
 virtual 10.10.10.10 udp 1812 service radius
 serverfarm SSGFARM
 idle radius request 20
 idle radius framed-ip 7200
 sticky radius framed-ip group 1
 inservice

The figure below shows a typical IOS SLB RADIUS load-balancing configuration for a CDMA2000 network with simple IP service. In this configuration:

• The RADIUS virtual server IP address for the PDSNs is 10.10.10.10.
• RADIUS requests are load-balanced between SSG RADIUS proxy servers 10.10.10.1 and 10.10.10.2.
• End-user data packets are routed to the IOS SLB device.
• End-user data packets from the 1.1.0.0 network are routed to the SSGs.

Figure 25. IOS SLB with RADIUS Load Balancing for a Simple IP CDMA2000 Network

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb route 1.1.0.0 255.255.0.0 framed-ip
!
ip slb serverfarm SSGFARM
  nat server
  real 10.10.10.1
    inservice
  real 10.10.10.2
    inservice
!
ip slb vserver RADIUS_SIP
  virtual 10.10.10.10 udp 0 service radius
  serverfarm SSGFARM
  idle radius framed-ip 3600
  sticky radius username
  sticky radius framed-ip
  inservice

The figure below shows a typical IOS SLB RADIUS load-balancing configuration for a CDMA2000 network with Mobile IP service. In this configuration:

• The RADIUS virtual server IP address for the PDSNs and the HA is 10.10.10.10.
• RADIUS requests are load-balanced between SSG RADIUS proxy servers 10.10.10.1 and 10.10.10.2.
• End-user data packets are routed to the IOS SLB device.
• End-user data packets from the 1.1.0.0 network are routed to the SSGs.

Figure 26. IOS SLB with RADIUS Load Balancing for a Mobile IP CDMA2000 Network

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb route 1.1.0.0 255.255.0.0 framed-ip
!
ip slb serverfarm SSGFARM
  nat server
  real 10.10.10.1
    inservice
  real 10.10.10.2
    inservice
!
ip slb vserver RADIUS_SIP
  virtual 10.10.10.10 udp 0 service radius
  serverfarm SSGFARM
  idle radius framed-ip 3600
  sticky radius username
  sticky radius framed-ip
  inservice

The following sample configuration enables IOS SLB to balance packet flows for a set of subscribers among multiple service gateway server farms (in this sample, a server farm of SSGs and a server farm of CSGs):

ip slb route 1.1.0.0 255.255.0.0 framed-ip
!
ip slb serverfarm SSGFARM
 nat server
 real 10.10.10.1
  inservice
 real 10.10.10.2
  inservice
!
ip slb serverfarm CSGFARM
 nat server
 real 20.20.20.1
  inservice
 real 20.20.20.2
  inservice
!
ip slb vserver SSG_AUTH
 virtual 10.10.10.10 udp 1812 service radius
 serverfarm SSGFARM
 idle radius request 20
 idle radius framed-ip 7200
 sticky radius framed-ip group 1
 access Vlan20 route framed-ip
 inservice
!
ip slb vserver SSG_ACCT
 virtual 10.10.10.10 udp 1813 service radius
 serverfarm SSGFARM
 idle radius request 20
 idle radius framed-ip 7200
 sticky radius framed-ip group 1
 access Vlan20 route framed-ip
 inservice
!
ip slb vserver CSG_ACCT
 virtual 20.20.20.20 udp 1813 service radius
 serverfarm CSGFARM
 idle radius request 25
 idle radius framed-ip 0
 sticky radius framed-ip
 access Vlan30 route framed-ip
 inservice

The figure below shows a RADIUS load balancing/firewall load balancing “sandwich” on one IOS SLB device. In this sample configuration:

• The RADIUS load balancing virtual IP address is 5.5.5.5.
• The subscriber framed-IP network is 1.0.0.0/255.0.0.0.
• VL105, VL106, VL107, and VL108 are VLANs.
• RADIUS requests arriving on VLAN VL105 are balanced to 10.10.106.42 and 10.10.106.43.
• User traffic is stickied based on framed-IP address assignments in the 1.0.0.0 subnet.
• Firewall load balancing on the other side (10.10.107.42/43) ensures that return path traffic to the subscriber is delivered to the correct gateway.

Figure 27. IOS SLB with RADIUS Load Balancing/Firewall Load Balancing “Sandwich”

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip vrf client
 rd 0:1
!
ip slb probe P742 ping
 address 10.10.107.42
 interval 120
!
ip slb probe P743 ping
 address 10.10.107.43
 interval 120
!
ip slb route 1.0.0.0 255.0.0.0 framed-ip
ip slb route framed-ip deny
!
ip slb firewallfarm SERVER
 access inbound Vlan108
 access outbound Vlan107
 inservice
 real 10.10.107.42
  probe P742
  inservice
 real 10.10.107.43
  probe P743
  inservice
 protocol tcp
  sticky 180 destination
 protocol datagram
  sticky 180 destination
 predictor hash address port
!
ip slb serverfarm SF1
 nat server
 access Vlan106
!
 real 10.10.106.42
  inservice
 real 10.10.106.43
  inservice
!
ip slb vserver VS1
 virtual 5.5.5.5 udp 0 service radius
 serverfarm SF1
 sticky radius framed-ip
 access Vlan105 route framed-ip
 access Vlan105
 inservice
!
mls flow ip interface-full
!
!*************************************************
!* Switchports, port channels and trunks         *
!* added to vlans 105-108 (left out for brevity) *
!*************************************************
!
interface Vlan105
 ip vrf forwarding client
 ip address 10.10.105.2 255.255.255.0
!
interface Vlan106
 ip vrf forwarding client
 ip address 10.10.106.2 255.255.255.0
!
interface Vlan107
 ip address 10.10.107.2 255.255.255.0
!
interface Vlan108
 ip address 10.10.108.2 255.255.255.0
!
ip route 10.10.105.0 255.255.255.0 10.10.107.42
ip route vrf client 10.10.108.0 255.255.255.0 10.10.106.42

The following sample configuration enables IOS SLB to support multiple server farms behind a RADIUS load balancing virtual server, using RADIUS calling station IDs and usernames to select server farms. Server farm farm3 is configured without an associated map, and therefore acts as a default server farm. If IOS SLB cannot match any of the other server farm maps, and a default server farm is configured, IOS SLB sends the RADIUS request to the default serverfarm.

ip slb serverfarm CSGFARM
 predictor route-map rlb-pbr
ip slb serverfarm AAAFARM
 nat server
 real 10.10.10.1
  inservice
 real 10.10.10.2
  inservice
ip slb vserver RADIUS_ACCT
 virtual 10.10.10.10 udp 1813 service radius
 serverfarm CSGFARM
 radius inject acct 1 key 0 cisco
 inservice	
ip slb vserver RADIUS_AUTH
 virtual 10.10.10.10 udp 1812 service radius
 serverfarm AAAFARM
 radius inject auth 1 calling-station-id
 radius inject auth timer 45
 radius inject auth vsa cisco
 inservice
!
interface vlan 100
 ip policy route-map rlb-pbr
!
access-list 1 permit 0.0.0.1 255.255.255.254 
access-list 2 permit 0.0.0.0 255.255.255.254 
!
route-map rlb-pbr permit 10
 match ip address 1
 set ip next-hop 10.10.10.1
!
route-map rlb-pbr permit 20
 match ip address 2
 set ip next-hop 10.10.10.2

The following IOS SLB configuration has the following characteristics:

• There is a virtual RADIUS server with IP address 10.10.10.10 that manages Network Access Server (NAS) devices.
• There are two packet gateways with IP addresses 10.10.10.1 and 10.10.10.2.
• RADIUS traffic destined for the virtual RADIUS server is distributed between the packet gateways, based on mapped framed-IP addresses, according to route map rlb-pbr.
• Server farm CSGFARM is configured with real IP addresses that match the possible results for route map rlb-pbr.
• End user traffic arriving on VLAN 100 is routed to the correct Cisco Content Services Gateway (CSG) based on access control lists (ACLs):
  • ACL 1 sends IP addresses ending in odd numbers to the CSGs behind packet gateway 10.10.10.1.
  • ACL 2 sends IP addresses ending in even numbers to the CSGs behind packet gateway 10.10.10.2.

Figure 28. IOS SLB with RADIUS Load Balancing Accelerated Data Plane Forwarding

Following are the IOS SLB configuration statements for the configuration shown in the figure above:

ip slb serverfarm CSGFARM
 predictor route-map rlb-pbr
ip slb serverfarm AAAFARM
 nat server
 real 10.10.10.1
  inservice
 real 10.10.10.2
  inservice
!
ip slb vserver RADIUS_ACCT
 virtual 10.10.10.10 udp 1813 service radius
 serverfarm CSGFARM
 radius inject acct 1 key 0 cisco
 inservice	
!
ip slb vserver RADIUS_AUTH
 virtual 10.10.10.10 udp 1812 service radius
 serverfarm AAAFARM
 radius inject auth 1 calling-station-id
 radius inject auth timer 45
 radius inject auth vsa cisco
 inservice
!
interface vlan 100
 ip policy route-map rlb-pbr
!
access-list 1 permit 0.0.0.1 255.255.255.254 
access-list 2 permit 0.0.0.0 255.255.255.254 
!
route-map rlb-pbr permit 10
 match ip address 1
 set ip next-hop 10.10.10.1
!
route-map rlb-pbr permit 20
 match ip address 2
 set ip next-hop 10.10.10.2