Fw: routed versus bridged interface

From: John Conzone (jkconzone@xxxxxxxx)
Date: Mon Sep 04 2000 - 11:38:44 GMT-3


   
   
   ----- Original Message -----
   From: John Conzone
   To: kkriel@netscape.net ; :ccielab@groupstudy.com
   Sent: Monday, September 04, 2000 10:17 AM
   Subject: Re: routed versus bridged interface
       Hi, Kenny. I understand that.
       What I am looking to do is break down the packets and go over
   exactly what is happening.
       If R1 is routing IPX , he looks in his routing table and see's IPX
   network 700 on E0. Good. So the packet goes out on R1 E0.
       R1 E0 is attached to R2 E0, which isn't routing IPX, but is in
   bridge group 1. So R2 E0 bridges the packet. Okay. R2 has another
   interface, Serial 0, which is in the same bridge group and isn't
   routing IPX. Good so R2 E0 bridges the packet over to R2 S0, which
   send it out its interface.
   So far so good?
       Okay. R2's S0 is directly attached to R3's S1. R3's S1is routing
   IPX and is on the same network, 700. He gets the packet that was
   bridged over from R2. It would sem to me that the bridged network in
   between the routed interfaces shouldbe transparent to them.
       I know i'm missing something. Is it the ethernet to serial
   conversion?
   
   ----- Original Message -----
   
   From: Kenneth Kriel
   
   To: John Conzone
   
   Sent: Monday, September 04, 2000 12:34 PM
   
   Subject: RE: routed versus bridged interface
   
   
   
   John,
   
   
   
   If you have routing and bridging enabled on an interface then it will
   route the frame and not bridge it. The rule is : when a router
   receives a frame - check if it is routable, if so pass it to the
   routing engine, if it is not then, and only then, bridge it.
   
   
   
   That is why it is working with IRB !
   
   
   
   Hope this helps !
   
   
   
   Ken
   
   -----Original Message-----
   From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
   John Conzone
   Sent: Sunday, September 03, 2000 11:14 PM
   To: ccielab
   Subject: routed versus bridged interface
   
       Guys, help me out again. Here's the scenario. I have three
   routers in a row.
   
   
   
       R1-----------R2------------R3
   
   
   
       On R1, I'm routing IPX on its interface connected to R2, as well
   as running bridging.
   
       On R2, I only have bridging on both interfaces. No ipx routing.
   
       On R3, I have IPX routing turned on onthe interface connected to
   R2, and also bridging.
   
   
   
       I cannot ping IPX bewteen R1 and R3. They are the same IPX
   network.
   
       If I configure IRB on R3, remove the IPX network from R3's
   interface, put it on the BVI on R3 and route IPX on the BVI and it
   works. The packets must be getting to R3 either way, but R3 cannot
   decapsulate them when routing directly on the interface becasue he is
   looking for a "routed" packet, but is recieveing a "bridged" packet
   from R2.
   
       Moving the IPX routing off the interface onto the BVI allows the
   "bridged"packet to be decapsulated and passed to the BVI as a "routed"
   packet.
   
       Can someone break out what the packet looks like coming out of R1,
   then out of R2 into R3?
   
       What is it specifically in the packet header , the "bridged"
   packet, that R3 see's when he tries to "route" the packet, that he
   doesn't like. I'm drawing a blank although in my gut I understand
   whats happening.
   
       I've run into this when binding a virtual interface on a RSP on a
   cat to a lane card, and then sending it to a router. I had to use BVI
   to get the 1483 "bridged" packet to route.
   
   
   
   
   
   
   
   



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