RE: QS: FIB and RIB: what is the difference

Narbik,

Thank you for this comprehensive reply.

One more thing I noticed during the debugs, that for every reply message,
router it telling me that it is routing via RIB. Why not FIB if corresponding
network entry is already maintained/populated/cached via FIB.

I am thinking, it is for the reason that traffic toward or locally generated
by the router is always process switched???

Thanks
Khalid

> Date: Fri, 25 Sep 2009 10:30:47 -0700
> Subject: Re: QS: FIB and RIB: what is the difference
> From: narbikk_at_gmail.com
> To: tvarriale_at_flamboyaninc.com
> CC: ccielab_at_groupstudy.com
>
> When you look at RIB and FIB you have to think of the 2 major and most
> important components of routing:
>
>
>
> - Control Plane
> - Data Plane
>
> The control plane takes care of the routing information exchange, and in
> MPLS environment, label exchange between adjacent devices.
>
> What do we have and see in the control plane? Routing protocols, exchange
of
> routing information, RIB (Routing Information Table) and once again in an
> MPLS environment you will also see a Label Exchange Protocol such as LDP.
>
>
>
> So therefore control plane builds a routing table or RIB based on the
> routing protocols.
>
> The control plane builds/populates 2 forwarding tables: a FIB (Which is
> built from the information in the RIB) and in MPLS networks an LFIB (Label
> Forwarding Information Base). These (FIB and LFIB) exist and work in the
> Data plane.
>
>
>
> The data Plane is simply a forwarding engine that is* independent* of the
> routing protocol or Label exchange protocol type; this Plane forwards
> packets to the appropriate interface based on the info found in the FIB or
> LFIB.
>
>
>
> So the way I envision it:
>
>
>
> You use a routing protocol to advertise routes upstreamand if any of the
> upstream routers need to connect to the advertised networks, they connect
> downstream toward the destination.
>
>
>
> Now this is a very brief and *basic* explanation of the RIB, FIB and LFIB.
>
>
>
> Now weather they are hardware based or software based I think is irrelevant
> when you look at different platforms.
>
>
> On Fri, Sep 25, 2009 at 9:24 AM, Tony Varriale
> <tvarriale_at_flamboyaninc.com>wrote:
>
> > That's making a poor assumption that the device you are speaking about is
> > hardware based.
> >
> > More than half of people won't come in contact with those devices (with
the
> > exception of a 6500).
> >
> > tv
> >
> > -----Original Message-----
> > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> > Anthony Sequeira
> > Sent: Friday, September 25, 2009 10:13 AM
> > To: Syed Khalid Ali
> > Cc: ccielab_at_groupstudy.com
> > Subject: Re: QS: FIB and RIB: what is the difference
> >
> > The Routing Information Base is the copy of the routing table stored
> > in software on the Cisco device.
> >
> > The Forwarding Information Base is the copy of the routing table
> > stored in hardware on the Cisco device.
> >
> > Thanks to Cisco Express Forwarding (CEF) and its use of the FIB,
> > performance for Cisco routers is much improved.
> >
> > Warmest Regards,
> >
> > Anthony J. Sequeira, CCIE #15626
> > http://www.INE.com <http://www.ine.com/>
> >
> > Test your Core Knowledge today!
> > Q: What protocol supports load-balancing with first-hop redundancy?
> > A: gateway load balancing protocol
> > More Info:
> >
> >
>
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ft_glbp.html
> >
> >
> > On Sep 25, 2009, at 10:47 AM, Syed Khalid Ali wrote:
> >
> > > dear group,
> > >
> > > I just started to prepare for R&S track. While going through the "ip
> > > packet
> > > debug command" these two terms just popped up.
> > > What is the difference between these two?
> > >
> > > Thanks
> > > Khalid
> > >
> > >
> > >
> > > _________________________________________________________________
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> >
> >
> >
> >
> >
> >
>
>
> --
> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> www.MicronicsTraining.com
> Sr. Technical Instructor
>
>
> Blogs and organic groups at http://www.ccie.net
>
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Received on Sat Sep 26 2009 - 00:34:05 ART