Avaya P333R-LB, Installation And Configuration Manual

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Chapter 14 Load Balancing in the P333R-LB
Avaya P333R-LB User’s Guide 51
In Figure 14.15, the same two Cache Servers are configured as Real Servers for
Server Load Balancing and for Application Redirection. Also, two Virtual Services
are configured: one is a SLB service for the non-transparent proxy cache
implementation, and the second is an AR service for the transparent cache
implementation.
Traffic destined to the proxy cache, is sent by the client to the VIP as the Destination
IP address, and dealt by the SLB Virtual Service (i.e., P333R-LB performs NAT on
the packets and sends them to the Real Server based on the configured metrics). If
the packets are to be forwarded to the Internet, P333R-LB receives the packets with
the Source IP address of the cache (since it is a non-spoofing cache) and routes them
to the Edge Router. On return, the packet is routed to the Real Server (since its IP
address is now the Destination IP address) and the cache sends the packet back to
the client.
Traffic not destined to the proxy cache, is sent with the Web Server’s IP address
(193.170.2.3) as the Destination IP address, and is processed by the AR Virtual
Service as usual, based on the second rule of the "ar-filter" statement.
The reason for the first "ar-filter" statement in the above configuration (
ar-filter
10 any 10.1.1.0 0.0.0.255 no-ar
) is as follows: both in the SLB and in the AR
cases it is possible that the packet is to be forwarded to the Web Server, if the
required data is not in the cache. Upon returning, usually packets from the Web-
server to the cache (in response to the non-transparent proxy cache SLB function)
would be load-balanced according to the AR service metric. To prevent this from
happening, the first "ar-filter" statement ensures that any packets destined to any of
the Real Servers (caches) are not subjected to Application Redirection but rather are
routed to the correct Real Server.