Cisco Cisco ACE Application Control Engine Module

A keepalive-appliance protocol (KAL-AP) on the ACE allows communication between the ACE and the 
Global Site Selector (GSS), which sends KAL-AP requests, to report the server states and loads for 
global-server load-balancing (GSLB) decisions. The ACE uses KAL-AP through a UDP connection to 
calculate weights and provide information for server availability to the KAL-AP device. The ACE acts 
as a server and listens for KAL-AP requests. When KAL-AP is initialized on the ACE, the ACE listens 
on the standard 5002 port for any KAL-AP requests. You cannot configure any other port.

The ACE supports VIP-based and tag-based KAL-AP probes. Previously, the ACE supported only 
tag-based KAL-AP for domains associated with VIP addresses. Through the domain, you could 
associate multiple VIP addresses with a tag with a maximum of 64 KAL-AP domain tags per context 
(see the Cisco Application Control Engine Module Server Load-Balancing Guide).

The KAL-AP tags per VIP address feature allows you to associate a KAL-AP tag with a VIP address in 
a policy map configuration. You can configure multiple VIP addresses to a tag or a VIP address to 
multiple tags. The ACE supports 4,096 VIP tags.

For information on configuring a VIP KAL-AP tag and displaying its load information, see the following 
sections:

For the domain load calculation, the ACE considers the Layer 3 class map, server farm, and real server 
objects. All other objects under the domain are ignored during the calculation. For the ACE A2(2.0) 
release, the calculation of the Layer 3 class-map has changed. Previously, the calculation considered 
each VIP address that is configured in the class map. A VIP-based KAL-AP calculation is run on each 
address. Now, the calculation consider all Layer 3 rules (a Layer 3 class map within a Layer 3 policy 
map) defined by the class map and sums up the total number of servers and the number of servers in the 
Up state. After determining these sums, the ACE multiplies them by the number of VIP addresses 
configured in the class map.

match http url

The HTTP URL match statement. 

hit

The number of times that a connection is established based on a specific URL match 
statement. 

The URL hit counter is per match statement per load-balancing Layer 7 
policy. If you are using the same combination of Layer 7 policy and class 
maps with URL match statements in different VIPs, the count is combined. 
If the ACE configuration exceeds 64K URL and load-balancing policy 
combinations, this counter displays NA.