[j-nsp] Duplicate IP addresses on interfaces

[Tony Stout]

Could this be useful in a situation where you have two links connected to
the same downstream device with Spanning Tree running to handle link failure
(active/passive).  That way, if the primary link fails, the standby link
will be configured with the same address once it becomes the active link?

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net
[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Richard A
Steenbergen
Sent: Tuesday, September 30, 2008 12:58 PM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] Duplicate IP addresses on interfaces

Once upon a time, Juniper did a sensible thing and didn't let you 
configure the same IP address on two different interfaces on the same 
router. Then at some point in the past (the earliest I've noticed it was 
8.2, but it could have been earlier), somehow the error check for this 
condition got changed from a hard error (which prevented the config from 
committing) to a warning (which still allows the commit to continue).

I can't find a single legitimate reason for this behavior to exist. It
doesn't let you use both interfaces simultaniously, it doesn't let you
pre-stage a circuit move so you can move the link from one port to
another, and as best as I can tell it either breaks routing on both
interfaces or at best arbitrarily allows one interface to work while
breaking all the rest. This is very clearly a problem, which allows a
simple typo to break routing for an existing interfaces, and yet in the
past year+ that I've been complaining about this Juniper has claimed
that it is functioning as designed and that it can't be PR'd.

At this point, I'm calling bullshit. Unless someone can come up with a 
legitimate reason for this behavior to exist, which seems highly 
unlikely, I'm pretty damn sure that this is a bug which needs fixing 
and I'd like the other users of this list to tell Juniper as much.