[j-nsp] default-address-selection not working?

[Lars Erik Gullerud]

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