Re: IRB (I thought I understood it until...!) posted 08/01/2000
- Subject: Re: IRB (I thought I understood it until...!)
- From: Alan Simpkins <alan_simpkins@xxxxxxxxx>
- Date: Tue, 1 Aug 2000 07:48:05 -0700 (PDT)
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@xxxxxxxxx> wrote:
> Let me see if I can explain myself better.
> The normal operation of bridging is to drop any
> that belongs to a protocol that is being routed on a
> router. That is why when you want to brige IP
> 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
> have IPX routing turned on R5. If IRB were not
> 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
> bridged traffic back into routed. This is done
> 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
> on others. You cannot route a protocol on on
> interface and bridge it on another. Bridged
> interfaces talk with bridged interfaces and routed -
> Hope this helps...
> William Swedberg CCNP CCDP
> --- Mark Lewis <markl11@xxxxxxxxxxx> 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
> > 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
> > Any ideas/doc.s to
> > reference?
> > Thanks in advance.
> > Mark
> > Get Your Private, Free E-mail from MSN Hotmail at
> > http://www.hotmail.com
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> William Swedberg CCNP CCDP
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