[j-nsp] Interface Index(ifIndex) changes when router is rebooted

[Paul Stewart]

Thanks -  yeah, I hadn't thought this all the way through ... was stuck in
the "Cisco world" for a bit where that option existed and got used to using
it ;)

Yes, our monitoring systems do update automatically come to think of it so
it's really a non-issue and you're right - "shit happens" and you have to
get this information updated anyways over time...

Cheers,

Paul


-----Original Message-----
From: Chris Adams [mailto:cmadams at hiwaay.net] 
Sent: Saturday, August 14, 2010 6:59 AM
To: Paul Stewart
Cc: 'martin'; juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] Interface Index(ifIndex) changes when router is
rebooted

Once upon a time, Paul Stewart <paul at paulstewart.org> said:
> I have to agree here - having the monitoring software "rediscover" where
the
> ifindex for an interface is after a reboot isn't ideal in my opinion.....

It is a case you have to handle anyway.  What if you upgrade REs, or you
have REs die and you have to replace them?  The index values will change
then anyway.  How do you handle that?  Do you manually update your
monitoring configs?

All the information is provided in SNMP, you just need to use it.  My
monitoring and management scripts walk and cache ifDescr to find the
desired interface and then use the ifIndex.  Every time they fetch
something for an interface, they include the ifDescr.  If the ifDescr
still matches, that's all it takes.  If it is different, the scripts
discards the ifDescr cache and re-walks the ifDescr tree.

This is one of the reasons I switched from MRTG to Cricket 10+ years
ago; I configure Cricket to graph "so-0/2/1", not "17".  Who knows what
"17" is; "so-0/2/1" is pretty obvious.

-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.