OK, looks like you are right according to that. I was reading from Bruce
Caslow's book. I'll go with Cisco.
Thanks for the correspondance Leigh Anne!
>>>Brian
>From: "Leigh Anne Chisholm" <[EMAIL PROTECTED]>
>Reply-To: <[EMAIL PROTECTED]>
>To: "Brian Lodwick" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]>
>Subject: RE: FR + Poison Reverse...
>Date: Tue, 27 Feb 2001 14:44:28 -0700
>
>Judging by the web page on Cisco's site
>(http://www.cisco.com/warp/public/779/smbiz/service/knowledge/wan/subifs.htm),
>it appears as if split-horizon is disabled for routing IP on physical
>(multipoint) interfaces as well as multipoint subinterfaces.
>
>Here's the part I'm referring to:
>
>"Note: For TCP/IP, Cisco routers can disable split-horizon limitations on
>all
>frame relay interfaces and multipoint subinterfaces and do this by default.
>However, split-horizon cannot be disabled for other protocols like IPX and
>AppleTalk. These other protocols must use subinterfaces if dynamic routing
>is
>desired."
>
>Out of curiosity, what is it that leads you to believe that split-horizon
>is
>enabled on frame relay subinterfaces?
>
>
>
> -- Leigh Anne
>
>
> > -----Original Message-----
> > From: Brian Lodwick [mailto:[EMAIL PROTECTED]]
> > Sent: February 27, 2001 1:45 PM
> > To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> > Subject: RE: FR + Poison Reverse...
> >
> >
> > Leigh Anne Chisholm,
> > Actually by default on IP interfaces:
> > Split-horizon is disabled on Frame-relay physical interfaces
> > Split-horizon is enabled on Frame-relay point-to-point and multipoint
> > subinterfaces
> > (but who cares it's configurable)
> >
> > There is a difference between a multipoint physical interface and a
> > multipoint subinterface. Althought there aren't too many
> > differences (static
> > mapping and dynamic mapping allowed on both) there are subtle
>differences.
> > My brother and I went over this yesterday and wondered what the
>differences
> > are. What we came down to was that the big difference is simple
> > -subinterfaces function is to provide a means to logically separate a
> > physical interface. The subtle differences like the default
>split-horizon
> > setting and default OSPF network type aren't the big differences. You
>can
> > build a fully scaleable hub spoke frame model using a physical
>multipoint
> > interface on the hub and point-to-point subinterfaces on the spokes. The
> > advantage of using the Multipoint subinterface on the hub? You would
>only
> > need 1 physical interface for 2 hub spoke frame models. I am interested
>in
> > learning more about other things you can do with the hub as a multipoint
> > subinterface to control traffic, such as for filtering or traffic
>shaping.
> >
> >
> > >>>Brian
> >
> >
> >
> >
> > >From: "Leigh Anne Chisholm" <[EMAIL PROTECTED]>
> > >Reply-To: <[EMAIL PROTECTED]>
> > >To: "Brian Lodwick" <[EMAIL PROTECTED]>, "Cisco@Groupstudy. Com"
> > ><[EMAIL PROTECTED]>
> > >Subject: RE: FR + Poison Reverse...
> > >Date: Tue, 27 Feb 2001 12:41:07 -0700
> > >
> > >Whoops! When I posted Excerpt 1, I missed the part in the first
>sentence
> > >that
> > >seems to imply that frame-relay interfaces and multipoint interfaces
> > >disable
> > >split-horizon BY DEFAULT (when using TCP/IP).
> > >
> > >When I took ICRC so many years ago, I remember discussing split-horizon
>but
> > >don't recall any explicit mention that split-horizon is disabled by
>default
> > >for the IP routing protocols (RIP and IGRP). I remember discussing
>this
> > >issue
> > >as well in CIT but I don't think the exception to the rule was noted
> > >either--but because I wasn't aware of it, it may have been something
>that
> > >went
> > >in one ear and out the other.
> > >
> > >It's interesting to note that in the current ICND curriculum, I know
>the
> > >section that talks about configuring subinterfaces indicates that
> > >"multipoint
> > >subinterfaces act as NBMA network so they do not resolve the split
>horizon
> > >issue". I don't have the entire official ICND curriculum available,
>but I
> > >don't notice anything specifically mentioning the exception.
> > >
> > >So, in summary - we're both right with respect to multipoint
>interfaces:
> > >
> > >With multipoint (or physical) interfaces: split horizon is ENABLED by
> > >default
> > >unless you are routing IP across the link. Then it is DISABLED. If
>you're
> > >routing using RIP, IGRP, or EIGRP to route IP, it's DISABLED. If
>you're
> > >routing IPX using RIP, EIGRP, NLSP, it's ENABLED. It's also enabled if
> > >routing AppleTalk.
> > >
> > >With point-to-point subinterfaces, split horizon is ENABLED but isn't
>much
> > >of
> > >an issue since it's a point-to-point link.
> > >
> > >
> > > -- Leigh Anne
>
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