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F5 Source IP connection Limit iRule

By   WirelessPhreak      Sunday, March 23, 2014      Labels: ,  

I came across an iRule that identifies multiple connection attempts from an IP address and throttle their connection. Because it is an iRule you can completely configure both the connection limit, timeouts, and even the message your F5 will send the user.

when RULE_INIT {
# This is the max requests allowed during "interval" specified below.
set static::maxRate 125;
# Below is the lifetime of the subtable record in seconds.
# This defines the interval during which requests are tallied. Example: Rate=10 and Timeout=3, allows 10 requests in 3 seconds
# Note: do not use very high timeout because it increases memory utilization especially under high load.
# Note: A rate of 100 in 50 seconds is the same is a rate of 20 in 1 second. But 1 second is a lot easier on memory,
# Because the records expire more quickly and the table does become too large.
set static::timeout 3;}
set getCount [table lookup -notouch -subtable requests [IP::client_addr]]
    if { $getCount equals "" } {
       # log local0. "New one:  getCount=$getCount [IP::client_addr] [clock seconds]"
       table set -subtable requests [IP::client_addr] "1" $static::timeout $static::timeout
       } else {
    if { $getCount < $static::maxRate } {
       table incr -notouch -subtable requests [IP::client_addr]
       } else {
    if {$getCount == $static::maxRate } {
       log local0. "User @ [IP::client_addr] [clock seconds] has reached $getCount requests in $static::timeout seconds."
       table incr -notouch -subtable requests [IP::client_addr]
   HTTP::respond 501 content "We apologize but your request/sec limit has exceeded the set threshold.  Please wait 30 seconds and refresh the page."

About WirelessPhreak

Just your everyday Packet Wrangler who enjoy's traveling and anything techie...