Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual download pdf (Page 105)

ServerIron ADX Advanced Server Load Balancing Guide 93

53-1002435-01

Sample configurations

To prevent this situation from occurring:

• Define the other interface on the cache server as a cache, but do not place the cache in a

cache group.

Policy-based cache failover

In some TCS configurations, the ServerIron ADX is connected to the clients and also to the Internet

through the same router. Moreover, in some cases the router contains a policy to forward HTTP

requests to a next-hop IP address (virtual IP address) if the packet containing the request matches

a filter configured in the router. Cache Failover (CFO) prevents client requests from becoming lost in

a “black hole” when the cache servers are unavailable. When you configure the ServerIron ADX for

CFO, the ServerIron ADX forwards client requests back to the router for forwarding to the Internet.

Thus, clients still receive the requested content even though the cache servers are unavailable.

Normally, cache groups on the ServerIron ADX do not have virtual IP addresses. Instead, the

ServerIron ADX selects a cache server from the cache group that contains the port to which the

router is connected. Within the cache group, the ServerIron ADX uses a hashing algorithm to select

a specific cache server.

NOTE

The virtual servers in SLB use virtual IP addresses, but TCS does not use virtual IP addresses unless

you are using CFO.

To configure CFO, make sure you do the following.

1. Set up the router and aim the policy on the router at the virtual address on the ServerIron ADX

rather than at the address of the cache.

2. Define the cache or caches on the ServerIron ADX and place them into cache group 1.

3. Define the virtual IP address in cache group 1.

4. Define the IP cache policy as a global cache.

NOTE

For CFO, you must define a global policy, not a local policy.

When you add the virtual IP address to the cache group:

• If the cache server to which the ServerIron ADX sends the HTTP traffic has the requested page,

the cache server sends the page back to the client, typically through the ServerIron ADX. (This

is the normal behavior regardless of whether you have added a virtual IP address.)

• If the cache server is unavailable or does not have the page and thus attempts to send the

request back through the ServerIron ADX to the Internet, the ServerIron ADX sends the request

to the router for forwarding to the Internet. If the virtual IP address is not configured on the

ServerIron ADX, the ServerIron ADX drops the request from the cache server.

Figure 24 shows an example of a configuration that requires CFO.

1 2 ... 100 101 102 103 104 105 106 107 108 109 110 ... 135 136

No comments

Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual Page 105