From: Carlos G Mendioroz (tron@xxxxxxxxxxx)
Date: Mon Jul 15 2002 - 06:58:39 GMT-3
I guess you could have more than 2 spokes, all level 2. Is that right ?
Brian McGahan wrote:
>
> Good point Fred. I'll have to add that one to my bag of tricks.
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> http://www.cyscoexpert.com
> Voice: 847.674.3392
> Fax: 847.674.2625
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Fred Ingham
> Sent: Sunday, July 14, 2002 6:26 PM
> To: Brian McGahan; 'Jonathan V Hays'; ccielab@groupstudy.com
> Subject: Re: ISIS - subinterface needed?
>
> Brian: I agree with your comments except for: " IS-IS will not run
> over a
> hub and spoke NBMA" Here is a counter example:
>
> Say that R1 is the hub with a multipoint subinterface. R2 and R3 are
> spokes using physical interfaces. All are in the same subnet, of
> course.
> Configure R1 as L1/L2 with net 49.0001.1111.1111.1111.00, R2 as L1 with
> net
> 49.0001.2222.2222.2222.00, and R3 as L1/L2 with net
> 49.0002.3333.3333.3333.00. Assuming you have CLNS maps on your frame
> cloud,
> and ip router isis on the serial interfaces, R1 will form an L1
> adjacency
> with R2 and an L2 adjacency with R3.
>
> This is part of an example that NMC-1 students configure with other
> routers
> connected off R2 and R3.
>
> Cheers, Fred
>
> ----- Original Message -----
> From: "Brian McGahan" <brian@cyscoexpert.com>
> To: "'Jonathan V Hays'" <jhays@jtan.com>; <ccielab@groupstudy.com>
> Sent: Friday, July 12, 2002 10:44 PM
> Subject: RE: ISIS - subinterface needed?
>
> > Johnathan,
> >
> > Actually there's a little more to it than that. With IS-IS,
> > there are only two network types, point-to-point and broadcast.
> Unlike
> > OSPF however, there is no equivalent of the 'ip ospf network' command.
> > The IS-IS network type is dependent on the interface type.
> >
> > Physical and multipoint NBMA interfaces are multipoint. The
> > only big difference between them is that split-horizon is disabled on
> > frame-relay physical interfaces. Point-to-point interfaces are (you
> > guessed it) point-to-point. Like OSPF, the IS-IS network type must
> > match for neighbors to become adjacent. Therefore, for two IS-IS
> > routers to become adjacent over NBMA, you need to have a combination
> of
> > physical and multipoint, or two point to point interfaces. This leads
> > us to two more issues that are worth mentioning.
> >
> > 1. IS-IS will not run over a hub and spoke NBMA
> > 2. IP is not the transport protocol for IS-IS
> >
> > In regards to the first issue, this means that you must have two
> > IP subnets if you are running a hub and spoke setup. Therefore you
> must
> > have two separate subinterfaces on the hub, or do a workaround such as
> a
> > GRE tunnel.
> >
> > Regarding the second issue, this means that physical and
> > multipoint interfaces must have layer 2 to CLNS mappings. For
> > frame-relay this translates to:
> >
> > frame-relay map clns [VC] broadcast
> >
> > This article should help to clarify some more.
> >
> > http://www.cisco.com/warp/public/97/isis-frint.html
> >
> > HTH,
> >
> > Brian McGahan, CCIE #8593
> > Director of Design and Implementation
> > brian@cyscoexpert.com
> >
> > CyscoExpert Corporation
> > Internetwork Consulting & Training
> > http://www.cyscoexpert.com
> > Voice: 847.674.3392
> > Fax: 847.674.2625
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Jonathan V Hays
> > Sent: Friday, July 12, 2002 5:11 PM
> > To: ccielab@groupstudy.com
> > Subject: RE: ISIS - subinterface needed?
> >
> > Thanks everyone for all the informative replies!
> >
> > Jonathan
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > Jonathan V Hays
> > Sent: Friday, July 12, 2002 2:17 PM
> > To: ccielab@groupstudy.com
> > Subject: ISIS - subinterface needed?
> >
> >
> > Group,
> >
> > I just had an interesting experience configuring ISIS on two routers.
> > One router (R1) had two serial subinterfaces, one of which was
> > point-to-point to another router running ISIS (R2). Now R2 was not
> > configured with subinterfaces, just "interface serial 0" since it was
> > only connected to R1 (via frame relay). I could not get ISIS routes to
> > appear in the routing tables of either router.
> >
> > After I changed R2 to a point-to-point subinterface the ISIS routes
> > popped into both routing tables.
> >
> > The question is, why is the point-to-point subinterface necessary on
> > both ends for ISIS to propagate routes?
> >
> > Jonathan
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