It is far more accurate to describe a layer 3 switch as a router. A router consists of a control function and forwarding function. In many modern routers, there is a single control processor and multiple forwarding engines.
Of the carrier-class routers where I am familiar with the internal design, there simply isn't as much of a distinction between layer 3 and layer 2 forwarding as much marketing material makes it out to be. The ingress forwarder looks up the destination address (and other things) in an appropriate hardware-assisted table, which, among other things, returns the desired output port. A header telling the fabric what to do with the packet or frame (e.g., send it to a port, multicast it to several ports) is prepended to the packet or frame, which is then handed off to the fabric. Most of the intelligence is on the input forwarder. The idea of physically separating the control and forwarding elements began with the AGS and autonomous switching, and has continued to develop. There is an IETF working group called FORCES that is looking at general protocols and architectures for such things as external control engines (i.e., external routers telling a switch how to forward). >Hi, > >The term "layer 3 switch" is used to describe a switch >that has routing capabilities. In the 6509, routing is >handled by the MSFC daughtercard on the Sup module. > >If you do a 'show module' the MSFC is in slot 15 >and/or 16. If you do a 'session 15' you >reverse-telnet/console into the router module from the >switch prompt if using Hybrid IOS. > >You don't need to route on the 6500 with the MSFC, you >could use a external router as well if you want but >the 6500+MSFC combo is faster. > >--- John Green wrote: >> Is it ok to refer to a "router" as a Layer 3 switch >> ? >> >> cisco 6500 was referred to as a Layer 3 switch. >> >> question: does it(6500) have routing capabilities ? >> >----------------------------------------------------- >> >> to connect to different vlans one needs a router. >> right ?? (as shown below) >> switchA --------ROUTER-------switchB >> >> but say some nodes connected to switchB are on the >> vlan of switchA. so now to connect switchA and >> switchB >> can router be ok ? > > ---------------------------------------------------- > -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** ******************************************************************************** Howard C. Berkowitz [EMAIL PROTECTED] Chief Technology Officer, GettLab/Gett Communications http://www.gettlabs.com Technical Director, CertificationZone.com http://www.certificationzone.com "retired" Certified Cisco Systems Instructor (CID) #93005 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38389&t=38358 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
