Mailing List Archive

default-address-selection not working?
Have a weird problem with one of our M40 routers. The box, like all our
Junipers, is configured with "system default-address-selection" to
source all RE-generated packets from lo0.0.

However, in this particular box, this seems to have stopped working for
some reason, and the router now picks the numerically lowest IP-address
configured on any interface as its source address. We only discovered
this when adding a new interface using an IP from a new netblock, since
the address used on lo0 was in fact previously the numerically lowest on
the system. Suddenly RADIUS, netflow and syslog-packets were being
dropped by our firewall because they originated from a different source.

When doing a "show interfaces snmp-index 0" to see the local IP's on the
box, the output differs on this box from our other routers in that the
lowest numerical IP will have "Flags: Is-Default" listed - none of our
other M40s or our M5s display this flag on any address.

We have tried removing the default-address-selection statement,
committing, and adding it again with no change in behaviour. It is
running JunOS 5.4R2.4 and has a current uptime of 203 days, and since it
is scheduled to be upgraded to 5.6 in a few weeks, I'd rather not have
to try to reboot it until then.

Has anyone ever had this problem before and know of a fix or a
workaround for this? I guess it is possible a reboot will cure the
problem, but again, I'd rather not have to do two reboots of the box in
within a short timeframe.

Any suggestions appreciated.

/leg
default-address-selection not working? [ In reply to ]
On 13 May 2003, Lars Erik Gullerud wrote:
> Have a weird problem with one of our M40 routers. The box, like all our
> Junipers, is configured with "system default-address-selection" to
> source all RE-generated packets from lo0.0.
>
> However, in this particular box, this seems to have stopped working for
> some reason, and the router now picks the numerically lowest IP-address
> configured on any interface as its source address. We only discovered
> this when adding a new interface using an IP from a new netblock, since
> the address used on lo0 was in fact previously the numerically lowest on
> the system. Suddenly RADIUS, netflow and syslog-packets were being
> dropped by our firewall because they originated from a different source.
>
> When doing a "show interfaces snmp-index 0" to see the local IP's on the
> box, the output differs on this box from our other routers in that the
> lowest numerical IP will have "Flags: Is-Default" listed - none of our
> other M40s or our M5s display this flag on any address.
>
> We have tried removing the default-address-selection statement,
> committing, and adding it again with no change in behaviour. It is
> running JunOS 5.4R2.4 and has a current uptime of 203 days, and since it
> is scheduled to be upgraded to 5.6 in a few weeks, I'd rather not have
> to try to reboot it until then.

Yes, we've had the same problem with 5.4R3 (though how it came to be is a
different issue); a reboot (and simultaneous upgrade to 5.6) fixed it.

Our screwup supposedly happened because 5.4 allowed you to configure an
lo0._1_ unit (and someone did that), but even though you removed it, it
would still screw up the default address selection until the reboot.
This has been prevented in 5.3 and 5.4, and now fixed in 5.4R4.

But, of course, this could be a different problem too.

--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
default-address-selection not working? [ In reply to ]
On Tue, 2003-05-13 at 18:45, Pekka Savola wrote:
> Yes, we've had the same problem with 5.4R3 (though how it came to be is a
> different issue); a reboot (and simultaneous upgrade to 5.6) fixed it.
>
> Our screwup supposedly happened because 5.4 allowed you to configure an
> lo0._1_ unit (and someone did that), but even though you removed it, it
> would still screw up the default address selection until the reboot.
> This has been prevented in 5.3 and 5.4, and now fixed in 5.4R4.
>
> But, of course, this could be a different problem too.

No, I believe you have correctly identified the problem. Some time quite
a while ago someone did in fact screw up and add a "unit 1" to lo0,
which was of course promptly removed again. This problem of course did
not manifest itself until now, since by coincidence the IP used on lo0.0
has been the lowest IP on the router until now. I guess I have to bite
the bullet and schedule a reboot which hopefully fixes this.

Thanks for your input.

/leg