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From: Lars Braeuer (lbraeuer_at_mpex.net)
Date: Wed 20 Nov 2002 - 18:12:13 GMT

John P. Eisenmenger wrote:

> On Thu, 14 Nov 2002, Lars Braeuer wrote:
> >I heared from someone else (the programer of heartbeat), that this
> >doesn't happen on his suse 7.3/8.0 boxes.
> I for one don't believe it.
> An interface with no associated route in the routing table is useless,
> except under special circumstances. A routing table entry is necessary
> for the system to select the proper interface (or next hop) for
> transmission. Ifconfig adds the routing entry on all UNIX platforms with
> which I've dealt (SunOS, Solaris, AIX, HP/UX, BSD, and Linux). If you
> really don't want the route to be added, then you need to remove the route
> after performing the ifconfig.

I also think it's normal, but I was a little confused by the answer of
the heartbeat programmer, stating that the behaviour of my system is
wrong, but after talking to several people I found out that it's just
the way it should be.

> Now if the assigned IP/netmask combines into a network that is already in
> the routing table, then the route might not be added. Perhaps this is the
> scenario being seen by the heartbeat developer.

well, this is the scenario it should be, but it isn't. when adding an
interface and a route is already present, another route is added. you
can only see differences when looking at ip route, it shows: "proto
kernel src link" on the new route.
looking at the kernel routing table shows no differences.

> >is anyone else of you experiencing the same.
> >
> >does anyone happen to know if this a kernel related problem?
> Well, I kind of object to this being called a problem. It is how things
> have worked for a long time in many implementations. A route table entry
> is necessary for the system to know where to send packets destined for (in
> your example) the 10.0.0.x network.

I agree, but somehow it should be possible to turn off that a route is

> Perhaps if I understood what exactly you were trying to do...

* add a route on system start
* no ip is assigned on boot
* when heartbeat is actived it assigns an ip address
   and looks for the right interface by checking the
   present routes in the routing table
* then it adds the ip address on the interface found
* this also adds "exactly" the same route as already present
* pinging an address in that net is impossible, as long as the
   two routes are present.
* removing one of the helps

I finally changed the sourcecode of the script that finds the interface,
so that it's able to also find interfaces using routes with different

thanks for your answer.


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