GroupStudy.com GroupStudy.com - A virtual community of network engineers
 Home  BookStore  StudyNotes  Links  Archives  StudyRooms  HelpWanted  Discounts  Login
Re: IRB (I thought I understood it until...!) posted 08/01/2000
[Chronological Index] [Thread Index] [Top] [Date Prev][Date Next] [Thread Prev][Thread Next]


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
> 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@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
> 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
> > 
> > 
> > 
> >
>
________________________________________________________________________
> > Get Your Private, Free E-mail from MSN Hotmail at
> > http://www.hotmail.com
> > 
> >
>
_______________________________________________________
> > To unsubscribe from the CCIELAB list, send a
> message
> > to
> > majordomo@xxxxxxxxxxxxxx with the body containing:
> > unsubscribe ccielab
> > 
> > 
> > 
> 
> 
> =====
> William Swedberg CCNP CCDP
> 
> __________________________________________________
> Do You Yahoo!?
> Kick off your party with Yahoo! Invites.
> http://invites.yahoo.com/
> 
>
_______________________________________________________
> To unsubscribe from the CCIELAB list, send a message
> to
> majordomo@xxxxxxxxxxxxxx with the body containing:
> unsubscribe ccielab


__________________________________________________
Do You Yahoo!?
Kick off your party with Yahoo! Invites.
http://invites.yahoo.com/

_______________________________________________________
To unsubscribe from the CCIELAB list, send a message to
majordomo@xxxxxxxxxxxxxx with the body containing:
unsubscribe ccielab