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RE: ISIS passive interface posted 08/04/2003
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 By putting the loopback interface in passive mode(passive interface
loopback 0), it is automatically made apart of the ISIS routing process.
This is not the same for other routing protocols. You can do "ip router
isis" on interface to put the loopback into the ISIS process, but this will
waste alot of CPU processing. When putting the lo0 interface in passive mode
under ISIS, you DO NOT need the "ip router isis" command on the loopback 0
to advertise into ISIS process.

-----Original Message-----
From: Tomasz Szymanski
To: Brian Dennis
Cc: 'Tim Fletcher'; ccielab@xxxxxxxxxxxxxx
Sent: 8/4/2003 5:05 PM
Subject: Re: ISIS passive interface

Are you sure Brian?
  I don't see "ip router isis" on Loopback interface so it's not in isis



Brian Dennis wrote:

>With IS-IS when you make the interface passive the router removes the
>"ip router is-is" command from under the interface. So in your case the
>loopback is still being advertised via IS-IS.
>Brian Dennis, CCIE #2210 (R&S/ISP Dial/Security) 
>-----Original Message-----
>From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
>Tim Fletcher
>Sent: Wednesday, January 29, 2003 11:53 AM
>To: ccielab@xxxxxxxxxxxxxx
>Subject: ISIS passive interface
>Hi all,
>shows the following config:
>interface Loopback0
>ip address
>!--- Creates loopback interface and assigns
>!--- IP address to interface Loopback0.
>interface Ethernet0
>ip address
>ip router isis
>!--- Assigns IP address to interface Ethernet0
>!--- and enables IS-IS for IP on the interface.
>router isis
>passive-interface Loopback0
>net 49.0001.1720.1600.1001.00
>!--- Enables the IS-IS process on the router,
>!--- makes loopback interface passive
>!--- (does not send IS-IS packets on interface),
>!--- and assigns area and system ID to router.
>My question is why would you need the passive-interface Lo0 command
>the ISIS config, when ISIS is not configured on Lo0? Isn't this
>-Tim Fletcher 

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