Technical data

ServerIron ADX Advanced Server Load Balancing Guide 127

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Interoperability issues with cache servers

NetCache servers

When the ServerIron ADX sends a packet to a NetCache server, by default the server addresses its

replies to the packet to the source MAC address of the packet, instead of replying to the MAC

address of the server's default gateway. This causes problems, especially in one-arm routing

configurations.

To work around this issue, enter the following commands on the NetCache server.

priv set advanced

show config.system.fast_ip.enable

set config.system.fast_ip.enable off

NetCache C720 cache server

This model of cache server sends HTTP error code 500 in response to an HTTP keep-alive health

check sent by the ServerIron ADX. By default, the ServerIron ADX does not consider this to be a

valid health check response. To work around this issue, configure status code 500 to be a valid

response to the health check. To do so, enter the port http status_code 500 500 command at the

configuration level for the cache server.

CSW with NetCache cache servers

When the ServerIron ADX redirects a TCP SYN to a cache server, the ServerIron ADX uses the

ServerIron ADX port's MAC address as the source MAC address and the cache server's MAC

address as the destination MAC address. The source and destination IP addresses are not

changed. The source IP address is the client's and the destination IP address is the website the

client is requesting.

When the ServerIron ADX receives the SYN-ACK from the cache server, the ServerIron ADX expects

the destination MAC address in the cache server's reply to belong to the destination IP address (the

requested Web site). The ServerIron ADX does not expect the destination MAC address to be the

ServerIron ADX port's MAC address.

If you are using a NetCache cache server, you must enable the server to respond appropriately to

the ServerIron ADX. To do so, access the following URL on the Netcache server:

• http:// cache_IP_address:3132/cache_config/ui_toggle_basic

On this page, disable IP Fast Output. When this feature is disabled, the cache server performs a

route lookup and sends the packet to the correct destination address.