You need to reset the each iterator. Using keys does that. Refactoring your code a little may help see what's going on. Consider:

use strict;

while (my ($defNet, $defKey) = each (%defMaskArray)) {
    ...

HOST:
    for (my $bCount = 1; $bCount <= $hostsN; $bCount++) {
        ...
        while (my ($n, $host) = each %$refHandle) {
            ...
        
        my $testResult = test ($bCount, $boundary, $host, $defNet, $de
+fKey, \@routeArray);
        
        keys %$refHandle if $testResult ne 'ok'; # Reset each
        redo HOST if $testResult eq 'retry';
        next HOST if $testResult eq 'greater';
        }
        
        ...
    }
}

sub test {
    my ($bCount, $boundary, $host, $defNet, $defKey, $routeArray, ) = 
+@_;
    
    for (my $iCount = 0; $iCount <= 256; $iCount = ($iCount + $boundar
+y)) {
        # evaluate boundaries
        if ($iCount == $host || (($iCount + $boundary) - 1) == $host) 
+{
            print OUT
                "$defNet for $host fell on a boundary for mask - $boun
+dary\n";
            if ($boundary == 256) {
                ...
            } else {
                ...
                return 'retry';
            }
        } elsif ($iCount > $host) {
            ...
            return 'greater';
        } else {
            ...
        }
    }
    
    return 'ok';
}
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Note too that you should use strictures (use strict; use warnings;) and generally avoid using $a and $b except for their magical use in the context of sort.