Cisco config checker

Phil Howard phil at
Mon Jan 4 18:17:04 UTC 1999

S.J.Brannon wrote:

> We have suggest to Cisco that if this tool is to be usable it must be in step with the IOS releases and regression tested.

IOS has inside a data representation of what it things the configuration
is (or should be).  It read it in and it can write it back out.  It is
that internal data structure, as complex and messy as it probably is,
having parts of the data scattered in so many modules, that really could
represent the delta.  Perhaps the only reliable way to do this is to do
it inside IOS itself.  With a new semantic of a config load that would
mean "replace the old config entirely with this config" (as opposed to
the existing semantic "merge this config with the old config") and the
IOS would do the right thing, this might work.  It would be a little bit
more black magic, but it would beat having to keep two different IOS
config interpreters in sync (the real IOS and the external tools).

> This tool can never tell if the real network will work

I don't think this problem will ever be truly solved by any means other
than the ones we use now (check it the best you can, have a fallback
plan, and go for it at a time of least disruption).

 --    *-----------------------------*      Phil Howard KA9WGN       *    --
  --   | Inturnet, Inc.              | Director of Internet Services |   --
   --  | Business Internet Solutions |       eng at        |  --
    -- *-----------------------------*      philh at       * --

More information about the NANOG mailing list