+<P>Initially when route filters were being tested we generated a
+"default" filter. Unfortunately it quickly became apparent that this
+might suit the UK cluster network but didn't really fit anybody else.
+However using a default filter is an appropriate thing to do. How, is
+explained further on.
+<P>
+<P>The first thing that you must do is determine whether you need to do route filtering <B>at all</B>. If you are a "normal" node with two or three partners
+and you arranged in an "official" non-looping tree type network, then <B>you do
+not need to do route filtering</B> and you will feel a lot better for not
+getting involved. If you are successfully using <I>isolation</I> then you
+also probably don't need to use route filtering.
+<P>
+<P>You will only require this functionality if you are
+"well-connected". What that means is that you are connected to several
+different parts of (say) the EU cluster and, at the same time, also
+connected to two or three places in the US which, in turn are
+connected back to the EU. This is called a "loop" and if you are
+seriously looped then you need filtering.
+<P>
+<P>I should at this stage give a little bit of background on filters. All
+the filters in Spider work in basically the same way. You can either
+accept or reject various options in order to create the filter rules
+you wish to achieve. Some filters are user settable, others can only
+be altered by the sysop. Route filtering can only be done by the sysop.
+<P>
+<P>
+Anyway, without further discouragement, let me start the process
+of explanation.
+<P>
+<H2><A NAME="ss1.3">1.3 The node_default filter</A>
+</H2>
+
+<P>All normal systems should have a default routing filter and it should
+usually be set to send only the normal, unlooped, view of your
+"national" network. Here in the UK that means nodes from the UK and
+Eire, in EU it is more complex as the networks there grew up in a more
+intertwined way.
+<P>
+<P>
+The generic commands are:-
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+reject/route node_default <filter_option>
+
+or
+
+accept/route node_default <filter_option>
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>where filter_option is one of the following ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+call <prefixes>
+call_dxcc <numbers>
+call_itu <numbers>
+call_zone <numbers>
+channel <prefixes>
+channel_dxcc <numbers>
+channel_itu <numbers>
+channel_zone <numbers>
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>Please be careful if you alter this setting, it will affect
+<B><I>ALL</I></B> your links!