Evans, TJ (BearingPoint) wrote: > > That all looks pretty good ... > > > On the MSFC/RSM - do a "show interface": (edited for length) > Vlan8 is up, line protocol is up > Hardware is Cat6k RP Virtual Ethernet, address is > 00d0.d335.6614 > > Vlan9 is up, line protocol is up > Hardware is Cat6k RP Virtual Ethernet, address is > 00d0.d335.6614 > So ... each 'router interface' has a MAC. The fact that it is > the same is > irrelevant as they are on different network/logical segments > on different broadcast domains>. > > So the frame comes in with a destination mac of 00d0.d335.6614, > and when > forwarded will leave with a source mac of 00d0.d335.6614 (same)
And that's exactly what would happen if you did the inter-VLAN routing on a router too, using subinterfaces for each VLAN/ IP subnet. :-) And, if it were a high-end router, it could do this at wire speed and would have a RIB and FIB, just like someone else described for the 6500. The 7500 router has had that sort of architecture for years, if I'm not mistaken. Howard has given us lots of examples of other high-end routers that have this sort of architecture. Of course, these high-end routers are probably way more expensive than the so-called L3 switch and probably have all sorts of features that you might not need in a campus network. So, we're back to the first answer. The difference between a router and a L3 switch is marketing. Also economics. Sorry, I just had to play devil's advocate. What a shame that Cisco has mangled this so much in their intro training materials. Priscilla > ... > > Does that help? > > Oh - and I think you meant to say "layer 3 switching" is a > marketing term, > not scientific or engineering in nature. ... you said "layer 3 > routing" ... > Thanks! > TJ > [EMAIL PROTECTED] > > > -----Original Message----- > From: DeVoe, Charles (PKI) [mailto:[EMAIL PROTECTED] > Sent: Wednesday, February 26, 2003 7:45 AM > To: [EMAIL PROTECTED] > Subject: RE: L3 Switching Huh???? [7:63728] > > OK, let me try this again. I am trying to figure out the > difference between > conventional layer 3 routing and layer 3 switching. A little > background. I > am currently working towards my CCNA (have been for about 3 > years). At any > rate, everything I read and look at says that > switching/bridging is a layer > 2 function, routing is a layer 3 function. > > Either I don't have a good grasp of the OSI model, switching, > routing, VLANs > or all of the above. > > The network: > > Host A 10.1.1.2 MAC 00.AA > Host B > 10.1.2.2 MAC 00.BB > | 10.1.1.1 MAC 01.AA 10.1.2.1 MAC > 02.BB | > switch > A-----------------------Router-------------------------switch B > 10.1.1.0/24 10.1.2.0/24 > > This is an ethernet network. Both segments are connected by a > traditional > router say a 2500. > In this instance the router interfaces are subnet A 10.1.1.1, > and subnet B > 10.1.2.1 > > For simplicity, assume ARP cache is empty. > Host A wishes to ping Host B > End user on Host A enters - ping 10.1.2.2 > The IP packet places the source address 10.1.1.2 and the > destination address > 10.1.2.2 into the packet. > The IP protocol examines the IP address and based on the IP > address > determines this is in another subnet. > An ARP request goes out for 10.1.1.1 (default gateway) and the > MAC address > is found. > The DLL then places the source MAC address 00.AA and the > destination MAC > 01.AA into the frame. > The frame then goes out the wire to the destination MAC. > The router interface sees this frame as destined for itself. It > de-encapsulates the frame removing the MAC addresses. The > router then > examines the IP address, based on the routing table it knows > the destination > port. > The router leaves the same IP source (10.1.1.2) and destination > (10.1.2.2) > in the packet. > The frame is rebuilt with the new MAC address of source 02.BB > and > destination 00.BB > Host B grabs this packet and does it's thing. > > Now, if I replace the router with a 6509 switch, with routing, > how does the > process change? > Said 6509 would be equipped with a 10/100 card so that the > hosts are now > directly connected. The router interface is now a virtual > interface, there > is no physical interface. Which is another question. How does > the 6509 > determine this virtual address? > > Am I correct? > Inter VLAN communication cannot occur without a router. > Switching is based on MAC address. > Routing is based on IP address. > > I believe the term "layer 3 routing" is a marketing term, not > scientific or > engineering in nature. > ****************************************************************************** > The information in this email is confidential and may be > legally > privileged. Access to this email by anyone other than the > intended addressee is unauthorized. If you are not the > intended > recipient of this message, any review, disclosure, copying, > distribution, retention, or any action taken or omitted to be > taken > in reliance on it is prohibited and may be unlawful. If you > are not > the intended recipient, please reply to or forward a copy of > this > message to the sender and delete the message, any attachments, > and any copies thereof from your system. > ****************************************************************************** > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63917&t=63728 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
