Difference between the Irules for redirection:

Hope this also give you some extra understanding on the getfield function.

Also you can playaround with the getfield, something like below.

when HTTP_REQUEST {
set VIP [getfield [HTTP::host] ":" 1]
set a [getfield $VIP "." 1]
set b [getfield $VIP "." 2]
set c [getfield $VIP "." 3]
set d [getfield $VIP "." 4] 
log local0. "$VIP - IP, $a $b $c $d"
}

When the VIP is directly accessed,So on the console this would log something like below, where ":" and "." are the delimiters. Hope this clarifies.

Rule /Common/test-rule : 20.30.40.50 - IP, 20 30 40 50