Configuring Server Load Balancing
IOS SLB Configuration Task List
IPC-145
Cisco IOS IP Configuration Guide
Configuring IOS SLB Dynamic Feedback Protocol
To configure IOSSLB DFP, use the following commands beginning in global configuration mode:
Configuring NAT
To configure IOSSLB NAT mode for a specific server farm, use the following commands beginning in
global configuration mode:
Implementing IOS SLB Stateless Backup
Stateless backup, based on the Hot Standby Router Protocol (HSRP), provides high network availability
by routing IP flows from hosts on Ethernet networks without relying on the availability of any single
Layer 3 switch. Stateless backup is particularly useful for hosts that do not support a router discovery
protocol (such as the Intermediate System-to-Intermediate System [IS-IS] Interdomain Routing Protocol
[IDRP]) and do not have the functionality to shift to a new Layer 3 switch when their selected Layer 3
switch reloads or loses power.

How IOS SLB Stateless Backup Works

A Layer 3 switch running HSRP detects a failure by sending and receiving multicast UDP hello packets.
When the IOS SLB switch running HSRP detects that the designated active Layer 3 switch has failed,
the selected backup Layer 3 switch assumes control of the HSRP group MAC and IP addresses. (You can
also select a new standby Layer 3 switch at that time.) Both the primary and the backup Layer3 switch
must be on the same subnetwork.
The chosen MAC and IP addresses must be unique and must not conflict with any others on the same
network segment. The MAC address is selected from a pool of Cisco MAC addresses. Configure the last
byte of the MAC address by using the HSRP group number. When HSRP is running, it selects an active
Layer 3 switch and instructs its device layer to listen on an additional (dummy) MAC address.
IOS SLB switching software supports HSRP over 10/100 Ethernet, Gigabit Ethernet, FEC, GEC, and
Bridge Group Virtual Interface (BVI) connections.
Command Purpose
Step1 Router(config)# ip slb dfp [password password
[timeout]]
Configures DFP and, optionally, sets a password
and initiates SLB DFP configuration mode.
Step2 Router(config-slb-dfp)# agent ip-address port [timeout
[retry-count [retry-interval]]]
Configures a DFP agent.
Command Purpose
Step1 Router(config)# ip slb serverfarm serverfarm-name Adds a server farm definition to the IOSSLB
configuration and initiates server farm
configuration mode.
Step2 Router(config-slb-sfarm)# nat server Configures server NAT.
Step3 Router(config-slb-sfarm)# real ip-address Identifies a real server to the IOSSLB function
and initiates real server configuration mode.