From: Rick Burts (burts@xxxxxxxxxxxxxx)
Date: Mon Jan 29 2001 - 09:29:34 GMT-3
Actually IGRP does not perform any lookups (neither classful
nor classless). IGRP helps build the routing table but does
not make the decision about how to forward packet data (that
is performed by a separate process).
The use of IP CLASSLESS does not influence what IGRP will
forward in its routing updates. IGRP will forward updates
utilizing the principles of a traditional classful routing
protocol (principles include: subnets should be contiguous,
forward subnet information within the network and summarize
at network boundaries, subnet mask information of updates
should conform to the mask of the interface forwarding the
update ie FLSM).
IP CLASSLESS influences the process that does the search of
the routing table and makes the forwarding decision (but that
is not the job of any routing protocol).
Rick
Rick Burts, CCSI CCIE 4615 burts@mentortech.com
Mentor Technologies 240-568-6500 ext 6652
133 National Business Parkway 240-568-6515 fax
Annapolis Junction, Md 20701
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On Sun, 28 Jan 2001, fwells12 wrote:
> IGRP only performs classful lookups anyway right? That is why you need to
> give it the IP Classless command to make it pass along anything it does not
> recognize to a default network or route etc.
>
> IGRP experts please clarify.
>
> ----- Original Message -----
> From: Jeremy Gray <jeremy.gray@virgin.net>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, January 28, 2001 1:08 PM
> Subject: RE: Igrp / ospf and redistribution - revisted
>
>
> >
> >
> > IGRP can be painful if you're used to more complex and forgiving
> protocols.
> >
> > In this instance it needs feeding with a default network. IGRP will
> > otherwise perform only strict classful lookups.
> >
> > ip default-network n.n.0.0
> >
> > Caslow recommends this route be a classful subnet 172.16.0.0 for example.
> > THe route is then tagged in show ip route as a 'candidate default route'
> > using an *.
> >
> > Your IGRP routers should then follow this network as though it where
> 0.0.0.0
> >
> > Jeremy.
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > D. J. Jones
> > Sent: 28 January 2001 17:57
> > To: Nigel Taylor; Connary, Julie Ann
> > Cc: ccielab@groupstudy.com
> > Subject: Re: Igrp / ospf and redistribution - revisted
> >
> >
> > Are you using the redistribute subnets under the ospf process for igrp?
> >
> > ----- Original Message -----
> > From: "Nigel Taylor" <nigel_taylor@hotmail.com>
> > To: "Connary, Julie Ann" <jconnary@cisco.com>
> > Cc: <ccielab@groupstudy.com>
> > Sent: Wednesday, January 24, 2001 7:48 AM
> > Subject: Igrp / ospf and redistribution - revisted
> >
> >
> > > Julie Ann,
> > > Here's the original mesage/layout of the scanerio I
> posted
> > > to
> > > the group. The lab also specified to only redistribute the OSPF domain
> > > routes into the IGRP domain. I do have "red ospf xx metric x x x x
> > x"
> > > under the IGRP process. Now I do get a 172.16.0.0/16 into the IGRP
> > > domain but I cannont ping all interfaces from the IGRP
> > > domain(another requirement).
> > >
> > > Now the lab also specifies "NO Statics". I'm also working on a
> > > OSPF - EIGRP - IGRP redistribution lab. In my case the lab required
> > > you to only use 172.17.59.x for the EIGRP and OSPF domains.
> > > The requirement called for the IGRP domain that is connected to
> > > use 171.68.62.93 w/ a 26 bit mask. Let's try some ASCII art.....
> > >
> > >
> > > EIGRP(E1)------R3 -------(S1)---(FR, Area 0)---R2 -----R1-(Area 1)
> > > / \
> > > / \
> > > IGRP OSPF(Area 2)
> > > (E0) (E2)
> > > / \
> > > R4 R5
> > > \
> > > (Area 3)
> > >
> > >
> > > Ok, I've got the EIGRP(E1) using 172.17.59.0/29. The OSPF domain is
> > > using 172.17.59.48/28(S1) and (E2) using 172.17.59.68/30. As I said the
> > > IGRP(E0) is assigned 171.68.62.93 w a /26 on R3's E0 interface. I've
> > > read through the list thread on this but I'm still unable to see a
> route
> > > to the OSPF from the IGRP domain. I'm so tired at this point can
> > > anyone shed some light on this for me...
> > >
> > > TIA
> > >
> > > Nigel...
> > >
> > >
> > >
> > >
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