An extension to the CISCO-SLB-EXT-MIB for SLB
health monitoring probes. 
        
SLB: Server Load Balancing. Server load balancing
provides for the balancing of packets and connections
arriving at the SLB device across a number of other
devices, such as real servers, firewalls, or caches.
A system containing an SLB device typically exhibits
higher performance, scalability, and reliability than
any of the devices being load balanced.  An SLB device
determines how to handle incoming frames and
connections according to the contents of incoming data
and various configuration options. In determining how
to handle incoming data, an SLB device may examine the
data at any OSI layer, including Layer 7.
        
This MIB includes information on the health monitoring
probes that can be used for monitoring the health of
real servers. Health checking provides the ability of 
the content switch to detect if a server is available 
for load balancing. Health probes used for health 
checking allow testing various application level 
functionality. The active probes are sent at regular 
intervals and the lack of a response can lead to a 
specific server or and entire group of servers being 
declared as not available.
        
 Following probes are based on TCP:
    http, https, smtp, telnet, ftp, tcp, 
    script, ldap, tacacs, sip, echo, finger.
 Following probes are based on UDP:
    tftp, udp, sip, echo,.
        
Acronyms and terms:
        
  SLB    Server Load Balancing
  VIP    Virtual Server IP address
  NAT    Network Address Translation
  SF     Serverfarm
  FT     Fault Tolerance
  SSL    Secure Sockets Layer
  TLS    Transport Layer Security                          
  Server Farm    : Contains cluster of Real Server         
  Real Server    : Real Servers are physical devices
                   assigned to a server farm.
                   Real  servers provide services that
                   are load balanced.
  Health Probe   : The mechanisms to monitor the health 
                   of real servers or rservers.
          Virtual IP          : The IP through which the real server is 
                                             reached during load balancing.
  Probe Instance : An instance of the probe identified by 
                                     cslbxProbeName. A probe instance is created
                                     for every probe association.
                                     For example: When a probe is associated with
                                     a real server a probe instance is created 
                                     for that probe.                                                    
  Probe Port     : This mechanism introduces the capability
          Inheritance      for the probe instance to inherit the 
                                     virtual ip address port or the 
                                     the real server port (identified by 
                                     cshMonServerfarmRealServerPort) when the
                                     probe port (identified by cslbxProbePort)
                                     is not configured.
                                     The precedence of inheritance is as follows
                                     1. Probe's configured port
                                     2. Real server port
                                     3. Virtual ip address port
                                     4. Probes default port identified by 
                                     cslbxProbePort.
                                     Examples:
                                     Scenario 1:
                                     Probe's configured port = 100
                                     Real server port = 200
                                     Virtual ip address port = 300
                                     Probe's default port = 80
                                     Inherited port of the probe instance = 100
                                     Scenario 2:
                                     Probe's configured port = not configured
                                     Real server port = 200
                                     Virtual ip address port = 300
                                     Probe's default port = 80
                                     Inherited port of the probe instance = 200
                                     Scenario 3:
                                     Probe's configured port = not configured
                                     Real server port = not configured
                                     Virtual ip address port = 300
                                     Probe's default port = 80
                                     Inherited port of the probe instance = 300
                                     Scenario 4:
                                     Probe's configured port = not configured
                                     Real server port = not configured
                                     Virtual ip address port = not configured
                                     Probe's default port = 80
                                     Inherited port of the probe instance = 80
                                     Scenario 5:
                                     There can be scenarios wherein there may
                                     be multiple inherited ports for a probe 
                                     instance.
                                     There are configurations where multiple virtual 
                                     ip addresses with different ports share the 
                                     same probe instance and the probe has no 
                                     configured port or real server port attached.
                                     In that case the shared probe instance has 
                                     multiple inherited ports. A typical scenario
                                     might be
                                     Probe's configured port = not configured
                                     Real server port = not configured
                                     Ports of the virtual ip addresses which
                                     shares the probe instance = 300,400 
                                     Probe's default port = 80
                                     Inherited port of the probe instance = 
                                     300,400