Load balancing amongst pool members while preserving ports

Hopefully I'm not overlooking an easy way to do this, but I need to load balance traffic amongst multiple pool members, but I need to preserve the port the traffic comes in and goes out on. Using the the provided port preservation doesn't seem to do this so I implemented an iRule that will always preserve the port the traffic was received on and will use the same port to send the received traffic out on. However, my iRule uses a primary and secondary node which has the destination IPs defined so it will always use the primary IP unless it's not able to connect then it will use the secondary. Is there an easy way to do this such as not setting any static entries? My iRule with minor edits is below:

 

 

when RULE_INIT {

 

Log debug messages to /var/log/ltm? 1=yes, 0=no

 

set static::disxd__pool_debug 1

 

 

Name of the pool where the pool members reside

 

set static::xd__pool pool__pool

 

 

Set primary and secondary guard nodes, these are the separate physical

 

servers that are already defined on the LTM. They should also have

 

associated pool members for the particular ports they are responsible for

 

set static::xd__pool_pri_node xxx.xxx.xxx.xxx

 

set static::xd__pool_sec_node xxx.xxx.xxx.xxx

 

}

 

 

when CLIENT_ACCEPTED {

 

 

set dst_port [TCP::local_port]

 

 

Try the primary pool member first

 

if { [LB::status pool $static::xd__pool member $static::xd__pool_pri_node $dst_port] ne "down" }

 

{ pool $static::xd__pool member $static::xd__pool_pri_node:$dst_port

 

if {$static::disxd__pool_debug} { log local0. "Request to $dst_port directed to $static::xd__pool_pri_node:$dst_port" }

 

return

 

 

Try the secondary pool member if the primary fails

 

 

}

 

elseif { [LB::status pool $static::xd__pool member $static::xd__pool_sec_node $dst_port] ne "down" }

 

{ pool $static::xd__pool member $static::xd__pool_sec_node:$dst_port

 

if {$static::disxd__pool_debug} { log local0. "Request to $dst_port directed to $static::xd__pool_sec_node:$dst_port" }

 

return

 

 

Both pool members failed, reject the packet and log the error

 

} else {

 

log local0. "FATAL ERROR: Both pool members ($static::xd__pool_pri_node:$dst_port and $static::xd__pool_sec_node:$dst_port appear to be down"

 

reject

 

}

 

}

 

 

Thx in advance!

 

D