>From my understanding in IS-IS a level-1/2 router will set the ATT bit on level-1 LSA's only when it has an active level-2 adjacency. All level-1 routers receiving an LSA with the ATT bit set will install a default route to the advertising router. In the event of multiple LSA's with the ATT bit set from different sources a level-1 router will install a default to the closest level-1/2 router. The purpose of the default-information originate within IS-IS is to have a method of manually overriding the ATT bit generated default routes. A default route generated by a router with default-information originate (regardless of level) will always be preferred over default routes generated by LSA's with the ATT bit set. A useful implementation of this would be when you want to default to a level-1 router for inter-network routing and route-leak into that level-1 area for intra-network routing.
HTH, -Michael Cohen -----Original Message----- From: John Matney To: [EMAIL PROTECTED] Sent: 6/13/02 12:45 AM Subject: Re: Default-info. originate in ISIS-Automatic?? [7:46380] In my experience, what you are seeing is correct. Every L1/L2 router sets the ATT bit in its LSPs. The L1 router see this and chooses the router with the lowest metric and ATT bit set as its default route. No additional configuration should be required. Hope this helps. On Wed, 12 Jun 2002, Cisco Nuts wrote: > Hello, > > Had a question on default-info originate in ISIS? Does a Level-1 router > automatically get a default route from a Level-1-2 router? I read somewhere > that you had to configure the default-info originate cmd. (similiar to in > OSPF) on a Level-1-2 router so it could advertise this to other Level-1 > routers inside the area. > > But in my case, when I do a sh ip route on a Level-1 router, I see a default > route pointing to the Level-1-2 router without me actually configuring this > command! Is this the case? > > Please advise. > > Level-1 router: > RTC#sh ip route > > > i*L1 0.0.0.0/0 [15/10] via 10.10.15.254, Multilink1 > > > This ip addr. 10.10.15.254 is the Level-2 router(Lo0) that this router > connects via a Multilink intf. > > > > > > _________________________________________________________________ > Join the worlds largest e-mail service with MSN Hotmail. > http://www.hotmail.com Note: The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. Thank you. ThruPoint, Inc. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=46573&t=46380 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
