[OLSR-users] Default routing question

John Gorkos (spam-protected)
Fri Mar 26 21:23:44 CET 2004

Snipped for brevity, important stuff left.

On Friday 26 March 2004 23:58, Andreas T√łnnesen wrote:
> Comments inline.
> >>
> >>John Gorkos wrote:
> >>>I have a project involving a large number of WRT54G routers running
> >>> linux w/ OLSR.  Perhaps 1 in 10 of the routers will have a backhaul to
> >>> the internet, the rest will use these internet connected routers as
> >>> gateways. The kicker is this:  I want to have a single configuration
> >>> that works on all routers, regardless of whether they are
> >>> internet-connected or not. Is this possible with the current OLSR
> >>> imlpementation?  From what I've been able to decipher, the OLSR daemon
> >>> finds out from the configuration file whether or not it is a "default"
> >>> router.  I need to determine this dynamically, because I don't know yet
> >>> which routers get an internet connection and which ones don't.
> >>
> >>IMO you should create a startupscript that checks wether the node has a
> >>internet route avalible. This check could easily be done inside the olsr
> >>daemon - but IMO this is not olsrs job. Modularity! :)
> >
> > But what if a route becomes available while olsrd is running.  For
> > example, I plug a DSL modem into the WAN jack of my WRT54G.  It detects
> > the insertion as a hotplug event, runs the DHCP client and receives an IP
> > address and a default route.  In my perfect world, olsr would "see" this
> > and reconfigure itself as a gateway node.  Am I pipe-dreaming?
> Ok - yout want a completley "plug and play" interface to the Internet
> gateway configuration...
> Well - a plugin could do this. Plugins will be supported from the next
> release(0.4.1) - and if you are interested I could write a plugin that
> dynamically checks for Internet routes and sets the node up as a gateway.
Well, that would be darn near perfect for me.  It would be easy to power-cycle 
the router when I plug in a new internet connection, but then there is the 
possibility of a race:  dhcpc usually forks, and what if olsrd is started 
before the dhcp configuration is complete?  the default route could be 
assigned mere milliseconds after olsrd runs, but by then it's too late.
> >
> >>Remember that you can tune the message-emission intervals to suit your
> >>mobillity-degree. If mobillity is high the HELLO(and other) intervals
> >>should be small.
> >
> > So in a fairly static network, is the converse true?
> I would say so. If mobility is low the control traffic emission
> intervals could be set up(longer intervals). This greatly reduces
> overhead - expecially for flooded traffic.
I'll experiment with values and report on the best that I find.
> >   I noticed that g/w address is one of the few parameters that MUST be
> > set in the configuration file vs on the command line.  Is there a reason
> > for that?
> The reason for this is that I never found it feasable to set HN routes
> at the commandline. I am trying to remove options that include passing
> lots of data(a node could be a gateway to several networks) from the
> commandline. No reason except that :) But I realize that in certain
> scenarios a configfile might not be avalible. If it is important to be
> able to set HNA routes at the commandline I could consider adding that
> feature.
That's fine.  I'd much prefer the ability to detect changes in a default route 
in real-time.

Thanks again for the responses.  I'm very excited at the possibility of a 
large-scale, open-source mesh networking platform based on cheap consumer 

John Gorkos

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