+<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 use
+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>To put it simply, you should not mix Isolation and Route Filtering. It
+will work, of sorts, but you will not get the expected results. If you
+are using Isolation sucessfully at the moment, do not get involved in
+Route Filtering unless you have a good supply of aspirin! Once you have
+started down the road of Route Filtering, do not use Isolation either.
+Use one or the other, not both.
+<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! Remember, this is a <I>default</I>
+filter for node connections, not a <I>per link</I> default.