A loopback interface is good for the following reasons:
- it is always up, so long as the router is reachable. Thus it just gives you
an interface to ping on the router that is not tied to a physical interface.
If you serial port goes down, and your BRI port comes up, Netview will still be
able to ping the loopback interface, and report reachability appropriately
(assuiming your routing converges.)
The other good things about loopback interfaces are that Netview will identify
the router by the DNS name assigned to the loopback interface, which means that
SNMP gets/sets/demand polls will work even if a physical intgerface is down.
Otherwise, if Netview knows a node as serial1.organization.com, then if that
interface goes down, all SNMP polls to that
router will fail, even if other interfaces are up and reachable.
Plus, if you use OSPF or BGP, using a loopback interface forces the choice of
the router ID to be the loopback interface. THis gives you more control and
stability in your routing protocols.
"Todd E. Lewis" wrote:
> I'm not really a router guy so what does the loopback port have to do with
> the BRI port ? According to our router guy, loopback is setup for DLSW (ATM
> Machine purposes). He's not sure either. Thanks.
>
> >>> Steve Francis <steve.francis@COMMSERV.UCSB.EDU> 05/18 2:15 PM >>>
> Probably an easier way to manage this situation is not to rely on rules.
>
> What I would do is create a loopback interface in the routers (always a good
> idea for a variety of reasons anyway). Manage the loopback and serial
> interfaces, but unmanage the ISDN interface.
>
> Then in normal state, your router will be green. If the serial interface
> dies and the ISDN works, it will be yellow (with a red serial and green
> loopback). If serial and ISDN fail, you get a red router.
>
> This is probably the behaviour you want.
>
> "Todd E. Lewis" wrote:
>
> > I guess what I mean is: when the 56kb line drops (thus turning the serial
> > interface red) the BRIO port should turn from red to green. Right now
> > netview is telling all the time that my BRIO ports are down when in fact
> > they should be down unless the 56kb link dies. Maybe the ruleset needs to
> > written in TEC. I'm not sure. I hope this is a little clearer.
> >
> > >>> James Shanks <James_Shanks@TIVOLI.COM> 05/18 12:23 PM >>>
> > Todd -
> >
> > Please elaborate more on what you are trying to accomplish.
> >
> > (1) What is your ruleset supposed to do? The scenario is not obvious to
> > me.
> >
> > (2) How do you propose to write the ruleset when there is no ruleset editor
> > on NT?
> >
> > James Shanks
> > Tivoli (NetView for UNIX) L3 Support
> >
> > "Todd E. Lewis" <telewis@PROVIDENTBANKMD.COM> on 05/18/99 11:44:42 AM
> >
> > Please respond to Discussion of IBM NetView and POLYCENTER Manager on
> > NetView <NV-L@UCSBVM.UCSB.EDU>
> >
> > To: NV-L@UCSBVM.UCSB.EDU
> > cc: (bcc: James Shanks/Tivoli Systems)
> > Subject: Ruleset for Netview NT 5.1.1
> >
> > We have cisco 2503 routers deployed in all of our bank branches. There's to
> > serial ports and one BRIO (ISDN Dial-up port).
> >
> > The serial port connects to a 56kb frame relay link. So a normal status of
> > the router should show serial port up and BRIO down. When the 56kb link
> > goes down the BRIO should dial-up to get the branch back online.
> >
> > I need help with writing a rule set that will cover the above scenerio. Any
> > help would be much appreciated, since I'm very green at writing rule sets.
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