From: Alan Simpkins (alan_simpkins@xxxxxxxxx)
Date: Tue Aug 01 2000 - 11:48:05 GMT-3
The key difference here is that traffic that is seen
on a bridged interface is visible to the routed
environment via a BVI with CRB a station on a bridged
segment cannot talk to a station on a routed segment.
--- William Swedberg <swedbergwp@yahoo.com> wrote:
> Let me see if I can explain myself better.
>
> The normal operation of bridging is to drop any
> packet
> that belongs to a protocol that is being routed on a
> router. That is why when you want to brige IP
> without
> IRB or CRB you issue the command "no ip routing".
>
> With IRB you are able to bridge a routed protocol on
> an interface while routing it on another. Under the
> IRB command you tell it what you want to route and
> what you don't. In the example of lab8b, you
> already
> have IPX routing turned on R5. If IRB were not
> turned
> on, all IPX traffic coming from R1 would be dropped.
>
> We turn on irb and the bridge interface will execpt
> the IPX traffic. Since we want the IPX 700 to
> propagate throughout the network, we need to turn
> this
> bridged traffic back into routed. This is done
> using
> the BVI interface. The bridged IPX traffic gets
> shuttled to the BVI which in turn ROUTES it to the
> other IPX routed interfaces.
>
> CRB allows you to route on some interfaces and
> brigde
> on others. You cannot route a protocol on on
> interface and bridge it on another. Bridged
> interfaces talk with bridged interfaces and routed -
> routed.
>
> Hope this helps...
>
> William Swedberg CCNP CCDP
>
> --- Mark Lewis <markl11@hotmail.com> wrote:
> >
> >
> > Hi people,
> >
> > This is a question about lab 8, so if you haven't
> > done it yet, avert your
> > eyes now !
> >
> >
> >
> > On lab 8b, you have to configure bridging between
> > the ethernet segment
> > connected to r1 & r7 and the serial connection
> > between r1 & r5. So far so
> > good. However, then you are required to configure
> > IRB on r5. Why? I was
> > under the (obviously mistaken) impression that
> with
> > IRB you use it with
> > multiple interfaces in a bridge-group and it
> > provides routing (ref. Cisco
> > LAN Switching (CiscoPress)). There's only one
> > interface in the bridge group
> > on r5. Is this something to do with encapsulation
> > ??!!
> >
> > I've checked the CD-ROM/Caslow/everywhere (I
> think).
> > Any ideas/doc.s to
> > reference?
> >
> > Thanks in advance.
> >
> > Mark
> >
> >
> >
> >
>
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