""Jens Neelsen"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi, > > a layer3 switch (e.g.3550-EMI) does not have layer3 interfaces. > All interfaces (Fastethernet and GigabitEthernet) are layer2 > interfaces. They can not have IP addresses.
gentle correction. by entering the "no switchport" command, one removes the particlar interface from the "L2" domain and into the L3 domain. At this point one can indeed enter IP address onto the physical inerfaces. I think you may be getting too carried away with L2 versus L3. A physical port exists in multiple layers of the OSI model, if you want to talk in terms of OSI. There is the physical port. There is whatever that physical port talks to and how. For example, an ethernet port has physical and mac layer characteristics. otherwise, how would it communicate with other devices on the wire? Add an IP address, and that port is now "L3" as well. A router with an ethernet interface plugged into a switch operates at all three "layers" of OSI. > > The VLANs are the (virtual) interfaces to the routing engine > (=layer3 switch). yes. good way of putting it. > > Layer2 interfaces are grouped into different VLANs and the > Layer3 switch (=Router) enables the communications between these > VLANs. one can also bridge between vlans, at least in the 3550 world. fallback bridging. > > A Router has to have different IP subnets on each interface. > Because the VLANs are the interfaces to the router, you need > different subnets on each VLAN. if you have subnet based vlans. remember that you can also have ip addressing on different ports, although, as you say, these all have to be on different subnets. unless you are etherchanneling, but that's a different story. but to get back to point here, what is the difference between a physical port configured with an IP address and a physical port assigned to a vlan, with the vlan having an ip address? > > With secondary IP adresses you can have more than one IP subnet > on a VLAN. But as with router interfaces the subnets of the > VLANs cannot overlap. > > A 5000 switch with RSM works in the same way. This is covered in > the Cisco BCMSN training course. > > With kind regards > Jens Neelsen > > --- Stephen Hoover wrote: > > > > Say for instance I have 2 hosts on the same layer 3 > > switch, but the > > > two > > > hosts are on 2 different IP subnets (No VLANs are defined). > > > > > > That's not possible! if you are talking about 2 IP subnet, > > than: > > > ------------------------- > > > actually it is by doing secondaries, but i would highly > > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > > > > Vicki, > > > > You mention the use of secondary IP's. On a L3 switch (a > > switch with the > > router engine in it) is it not possible to define Ethernet sub > > interfaces > > instead of using secondary IPs - without VLANs defined? > > > > > > I'm sorry to be so thick, I'm just not getting it. If a L3 > > switch (with > > a routing module/engine in it) is essentially a wire speed > > router, then the > > VLAN just seems like an additional identifier on top of the L3 > > address - and > > doesn't really serve any purpose. In my previous example, 2 > > hosts on the > > same L3 switch, but on 2 different IP subnets - wouldn't a > > defined Ethernet > > subinterface be each clients respective gateway, and thus > > normal L3 routing > > would occur, just at switch speeds???? > > > > > > Thanks again! > > > > Stephen Hoover > > Dallas, Texas > [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63185&t=63147 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
