From: W. Alan Robertson (warobertson@xxxxxxxxxxxxx)
Date: Mon Nov 05 2001 - 22:26:14 GMT-3
Close, but not quite.
The "always" keyword has nothing to do with the routing table of the
router upon which it is configured. It only affects the behaviour of
what that router advertises to it's OSPF neighbors.
When the "default-information originate always" is used, it does just
that... That router advertises the 0.0.0.0/0 route to all of it's
OSPF neighbors, and this route will be carried throughout the routing
domain.
The consequence of this is that if the advertising router doesn't
actually have a default gateway, you have successfully blackholed the
Internet (Or any route less specific than what you have in the routing
tables throughout your routing domain).
This may be ok, in certain circumstances... If the router which uses
the "always" keyword is the only way out of the network, for example,
but the circuit drops periodically, it's probably ok that you continue
to advertise the route. It becomes a matter of personal preference;
you are deciding where non-routable packets hit the bit-bucket. If
your routing domain has a highly utilized serial connections of
varying speeds (which is likely), you may find it bettter that
non-routable traffic get dropped closer to the source, so as not to
utilize precious bandwidth within your enterprise.
Hope this helps...
Alan
----- Original Message -----
From: "Chris Larson" <clarson52@home.com>
To: "Joe" <joe.morabito@home.com>; <ccielab@groupstudy.com>
Sent: Wednesday, December 05, 2001 6:20 PM
Subject: Re: When to use "always"
> I do not understand what you are saying Cisco said, but my
understanding of
> this is that the default route will remain in the table regardless
of
> whether the next hop appear in the table or not.
>
> So if you had something like
>
> ip route 0.0.0.0 0.0.0.0 192.168.1.1
>
> and the 192.168.1.1 route was not in the table the default route
would
> disappear (ie. floating static ).
>
> by adding the keyword always the default route would remain in the
table
> whether a route to 192.168.1.1 was there or not. I would imagine if
the
> default info originate has the same keyword it works the same way.
>
>
>
>
> ----- Original Message -----
> From: "Joe" <joe.morabito@home.com>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, December 05, 2001 4:01 PM
> Subject: When to use "always"
>
>
> > Can someone please help me understand when exactly to use "always"
when
> > injecting a default route into ospf?
> >
> > CCO says that "always" disregards the requirement of already
having a
> default
> > route for the router itself. If this is true, and you don't have
"ip
> route
> > 0.0.0.0 0.0.0.0 x.x.x.x" and you are not using a route map, then
will it
> still
> > work?
> >
> > Thanks.
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