At 9:23 PM -0400 6/22/02, Priscilla Oppenheimer wrote: >There might be a Howard-inspired lesson in this. ;-)
If you're referring to the insight the U/C/M plane model gives to understanding protocols, you're absolutely right. It adds depth that the basic OSI model does not. For that matter, of course, Cisco, in its courseware, ignores the additional ISO interpretive/extension documents. > >In the Control Plane, the host ARPs for its default gateway, which in this >case is configured to be the HSRP virtual IP address of the routers. Exactly. Control Plane protocols [1] run between hosts and local routers/switches. [1] The U/C/M model is the original one from Broadband ISDN/ATM. In the IETF, there's some tendency to merge C and M plane functions, which I think is a bad idea. OTOH, I've designed routers that had ARP and routing protocols running in the same non-forwarding processors, and I think of that as coexistence of C and M planes. > >In the Management Plane, the routers talk amongst themselves to make sure >that the virtual IP and MAC addresses stay live. Yep. Management Plane protocols run between network elements like routers and switches. That HSRP may run over the same physical medium as the hosts doesn't make it control plane. > >In the User Plane, the host sends user traffic (Ping in my case) and the >routers forward traffic, without regards to HSRP. Sure, the host uses the >virtual MAC address as its destination, but it doesn't know there's >anything virtual about it. The routers forward the reply without any >concerns about HSRP. > >I did run this on some rather old routers running IOS 11.0, but I'm pretty >sure the results would be the same on newer IOS (although you can get an >HSRP-configured router to do ICMP Redirects now.) Also, it wasn't exactly >the scenario the original poster asked about, in that he seemed to be >implying the source and dest were out the same interface on the router, and >he was asking about just the request maybe, whereas I got the reply >involved. His exact scenario was harder to set up. Hmmmmm. I'll give it a >try. Unfortunately, my routers don't do VLANs (too old), but I could try it >with secondary addresses. > >OK, tried it, same result. The only time you see the virtual MAC address is >on the original request from the host. Forwarded requests and replies don't >use it. > >Gotta run. I really do have a life outside my lab?! ;-) > >Priscilla > >At 08:31 PM 6/22/02, Michael L. Williams wrote: >>"Priscilla Oppenheimer" wrote in message >>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> > At 12:17 AM 6/22/02, Tim Potier wrote: >> > >Lets say I have HSRP configured on a series of routers... I know clients >>are >> > >sending packets to the MAC/IP of the well known "virtual MAC" with Cisco >> > >equipment. Assume the receiving station recieves the packet directly >>from >> > >the router participating in HSRP with the highest priority... what is >the >> > >source MAC the receiving station sees? >> > >> > The reply will come from the actual MAC address of the router interface. >>At >> > this point, the router is just forwarding packets. It doesn't care that >> > HSRP is configured >> >>I was thinking the same thing. Sure, a client that sends to the Virtual IP >>for the HSRP gateway uses the virtual MAC to send to, but as far as return >>traffic, it seems the router would just receive the packet, lookup which >>interface it should go out, then rewrite the source/dest MACs in the frame >>and send it out.... no HSRP involved.... >> > >Mike W. -- "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=47240&t=47240 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
