Chris P - Chris H and I are saying the same thing.
However, regarding the network diagram you shared... Comment 1: Node Chianti L1 only Area Address 49.0001 Node Cabernet L1 only Area Address 49.0003 There is no connectivity directly between these nodes. No adjacency can be formed on the link connecting them because they do not have an area address in common and they only support L1. (Chris H - I do not see " multiple area IDs" configured on any router.) Comment 2: The L2 sub-domain in your network consists of: Riesling---Merlot---Shiraz---Chardonnay Only L2 traffic will flow over these links. There is no "area address" associated with the L2 sub-domain. It consists of L2 capable routers who also operate as L1 routers in their respective areas. As shown, there are no L1 links in area 49.0002. Given this, you could assign different area addresses to Merlot and Shiraz and it would have no impact on traffic. Les > -----Original Message----- > From: Christian Hopps <[email protected]> > Sent: Wednesday, February 15, 2023 4:54 AM > To: Chris Parker <[email protected]> > Cc: Christian Hopps <[email protected]>; Shraddha Hegde > <[email protected]>; Les Ginsberg (ginsberg) <[email protected]>; > Acee Lindem <[email protected]>; [email protected] > Subject: Re: [Lsr] Two small potential typing errors in > draft-ietf-lsr-flex-algo > > > Chris Parker <[email protected]> writes: > > > Hi there Christian, > > > > Thank you very much for your comments there. > > > > Perhaps I'm not using precisely terminology, but I've configured an > > L1 router to be part of multiple IS-IS areas at once. > > > > I'll quote from a 2005 book to show you this topology: https:// > > www.networkfuntimes.com/wp-content/uploads/2018/07/ > > Multi-area-ISIS-router-Pt1-768x407.jpg > > > > If the following configuration is added to the bottom-left router, > > then both the 49.0001 and 49.0003 adjacencies come up. The result is, > > I was led to believe, a single L1 topology that contains two IS-IS > > areas. https://www.networkfuntimes.com/wp-content/uploads/2018/07/ > > Multi-area-ISIS-router-Pt2.jpg > > > > I think this counts as one router being in two areas at once - but if > > I'm not using precise language, or if I'm misunderstood you, then > > please forgive me. > > It's easy to be confused by this; however, this is the multiple area IDs for a > single area case I mentioned in my "P.S." > > By configuring your bottom left router with multiple area IDs you have > effectively merged those 2 areas into a single area. For more information on > this check out ISO 10589:2002 section 7.1.5 "Manual area addresses" which > starts: > > 7.1.5 Manual area addresses: > > Within a routeing domain, it is often convenient to associate > more than one area address with an area. > > > Thanks, > Chris. > [as wg-member] > > > > > All the best > > Chris > > > > > > On Wed, Feb 15, 2023 at 10:16 AM Christian Hopps <[email protected]> > > wrote: > > > > Hi Chris, > > > > Just want to note one mis-undertanding below.. > > > > Chris Parker <[email protected]> writes: > > > > > Even if we were to talk about level 1, it is possible for an L1 > > > router to be in two IS-IS areas at once, which is a way of > > creating a > > > single L1 topology, a single LSP flooding domain. > > > > An IS-IS router instance can only be in one area not multiple. > > IS-IS differs from OSPF in that area boundaries exist "on the > > wire" (i.e., between routers) and not inside the router instance > > as they do with OSPF. An IS-IS router instance is only ever in > > one area. > > > > Thanks, > > Chris. > > [as wg-member] > > > > P.S. I don't think you are referring to the ability in IS-IS to > > refer to an area with multiple identifiers.. _______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
