ACE Load Balancer: Configure the Load-Balancing Service

There are quite a few ways to structure the configuration of the Load Balancing Service on a Cisco ACE device, or a Load Balancer (LB). The official Cisco documentation can be a bit overwhelming, as you can see here. Heres the approach that I´ve always found simple to understand.Step 1
Define the REAL SERVERS (rservers or physical servers) that will participate the Load-Balancing process. The number of Real Servers (rservers) within the Server Farm can vary, where 1 server would logically be the minimum, and the maximum depend on the Balancer model. In this example two Real Servers are configured, with names SERVERCISQUEROS03 and SERVERCISQUEROS04, and the respective IP Addresses 10.187.4.42 and 10.187.4.43.

Define the ratio between the Real Servers in the farm using the "weight X" command. In this case the value X will be 1, so the load will be equally ballanced between the two servers.

From the Global Configuration mode:

 rserver host SERVERCISQUEROS03
 ip address 10.187.4.42
 weight 1
 inservice


 rserver host SERVERCISQUEROS04
 ip address 10.187.4.43
 weight 1
 inservice


Step 2Define the PROBE. The Probe helps the balancer verify that the Real Servers are available, and providing the Service that we are trying to establish using the exact physical PORT (9080 in this case).

The probe can be TCP, Http, Https... Be careful here! This defines the connection between your ACE and the Real Servers, not between the Client and the Real Server, so make sure how your servers are configured.

In this example I did the http probe that uses the GET method, and goes for /Index.html on the server.

 probe http web_cisqueros.blogspot.com
  port 9080
  interval 30
  faildetect 2
  request method get url /index.html
  expect status 200 200

Other attributes I used in the configuration:

interval 30 #Probe gets launched against the server every 30 seconds faildetect 2 #If the probe fails to get the response from the server twice, it changes the state to "FAILED"expect status 200 200 #Status the probe expects from the Real Server (2xx codes indicate success)


Step 3

Define the SERVER FARM that will inter-connect the two connected Real Servers with the configured Probe. Put both of the configured rservers "in service".

serverfarm host SRV_cisqueros.blogspot.com
 description *** Cisqueros Server Farm ***
 predictor roundrobin
 probe web_cisqueros.blogspot.com
 rserver SERVERCISQUEROS03 9080
  inservice
 rserver SERVERCISQUEROS04 9080
  inservice


Step 4

Define the Layer 7 Policy Map to specify the match criteria and action, and relate it to your Server Farm.

 policy-map type loadbalance first-match PM-VIP-cisqueros.blogspot.com
  class class-default   serverfarm SRV_cisqueros.blogspot.com


Step 5

Define the Layer L3-L4 Class Map to specify the LB match criteria applied to input traffic. Be sure to know the Load Balancing Service VIP (Virtual IP) address beforehand.

 class-map match-all VIP-cisqueros.blogspot.com
  2 match virtual-address 10.187.4.111 tcp eq 9080

*The number "2" is due to the configuration Best-Practice, its a rule sequence number and this way we can modify the Class Map later adding the 1st rule

Step 6

Define, or use the already existing L3-L4 Policy Map that you are using for the other Balanced Services. Within it define the Class Map for this particular Load Balancing Service, and connect it to the already configured Layer 7 Policy Map.

 policy-map multi-match PM-VIP
  class VIP-cisqueros.blogspot.com
   loadbalance vip inservice
   loadbalance policy PM-VIP-cisqueros.blogspot.com
   loadbalance vip icmp-reply active

Some commands to check the validity of the configured Server Farm and Probe:

 #show probe web_cisqueros.blogspot.com [details]

 #show serverfarm SRV_cisqueros.blogspot.com