GNS3 has it's benefits in terms of being able to test out reasonably complicated scenarios in terms of routing. But it does have it's quirks and issues.
One issue with the GNS3 0.8.4-RC2 release is in how it deals with its topology file. Well,
now that I think of it, there are two issues I recently encountered with this build. If others
encounter the same thing, I've included some work arounds.
The first issue I encountered is that when I built a topology, there were a few routers
for which I did not create links. When I saved and then reloaded the topology file, the
unlinked routers did not show up on the diagram. So.... whenever adding routers, ensure
there is at least one link provided. This ensures that router shows up next time in the drawing.
The second issue is somewhat more insidious. A reasonably complicated set of routers
and links can be created. The topology can then be saved. When restarting it a subsequent time,
the following error occurs:
*** Warning: Connecting to resulted in:
206-unable to create UDP NIO
*** Error: errors during loading of the topology file, please correct them
The solution to this is to manually edit the topology file and reorder the sections in
ascending order, something like:
127.0.0.1:7200]
... section content
[127.0.0.1:7201]
... section content
... simlar sections