Troubleshooting guide

1-12
Cisco Wide Area Application Services Configuration Guide
OL-26579-01
Chapter 1 Configuring Traffic Interception
Configuring WCCP on WAEs
Note In a WAAS AppNav deployment, only the ANCs are included in the service group and are load balanced
by the routers. The routers do not send traffic to the optimizing WAEs (WNGs); instead, ANCs distribute
traffic to the optimizing WNGs.
You can use load balancing to balance the traffic load across multiple WAEs. Load balancing allows the
set of hash address buckets assigned to a WAE to be adjusted, shifting the load from an overwhelmed
WAE to other WAEs that have available capacity. Two assignment methods are used by this technique:
hashing and masking.
Assignment method denotes the method used by WCCP to perform load distribution across WAEs. The
two possible load-balancing assignment methods are hashing and masking. If the mask load-balancing
method is not specified, then the hash load-balancing method, which is the default method, is used.
Note In a WAAS AppNav deployment, only the mask assignment method is supported and is the default.
WCCP supports redirection based on a hash function. The hash key may be based on the source or
destination IP address of the packet. For WAAS, load-balancing hashing is based on a source IP address
(default), a destination IP address, or both.
The hash function uses the source IP address to obtain an address bucket to which the packet is assigned.
These source address buckets are then mapped to a particular WAE depending on how many WAEs are
present and how busy they are. (See Figure 1-2.)
Figure 1-2 Load Balancing Through Hashing of IP Addresses
Note Packets that the WAEs do not service are tunneled back to the same router from which they were
received. When a router receives a formerly redirected packet, it knows not to redirect it again.
255
...
171 170
...
86
...
1
85
Hash
4 billion 0
Address
buckets
171-255
Address
buckets
86-170
Address
buckets
1-85
WAE1
WAE3
WAE2
WCCP Version 2-
enabled router
32-bit IP addresses
159090