At 9:21 PM -0400 6/23/02, Kevin Cullimore wrote: >It's a problem when: > >people assume that symmetry exists when HSRP & similar L3 failover >technologies are implemented. > >It's a problem getting in the way of: > >people's understanding of those failover technologies. > >Otherwise, I'm thinking that the flexibility (wherein conversations in >different directions may be treated differently) is quite welcome. > >Comments?
I was not assuming load-sharing (i.e., multiple HSRP groups), so I'd expect to have the two routers essentially with the same routing table. What would be different would be their uplinks, unless, possibly, there were an additional link connecting the two routers. In other words, I had considered the simple case of two redundant routers, each of which could handle the full load. Perhaps they might have physically diverse uplinks, but I wouldn't expect them to have radically different optimal routes. Certainly, one can create scenarios where load-sharing or other factors make the two routers significantly different. Depending on the goals and budget, you might even have HSRP in edge routers and more complex routing at a distribution tier. For that matter, people often don't consider L2 failover techniques (e.g., UplinkFast and EtherChannel) with switches feeding the HSRP routers as another aspect of no-single-point-of-failure. > >----- Original Message ----- >From: "Howard C. Berkowitz" >To: >Sent: 23 June 2002 3:54 pm >Subject: Re: Re: HSRP [7:47177] > > >> At 3:08 PM -0400 6/23/02, Kevin Cullimore wrote: >> >A useful notion to keep in mind is that hsrp and its un-patented >> >counterparts (you'd think that during the past century, people would >learn >> >from IBM's example, but apparently that isn't the case) are profoundly >> >asymmetric in scope: >> > >> >they are concerned with the host->default gateway portion of the >> >conversation, not the return path (although implementational specifics >might >> >force them to address the return path in some circumstances). >> >> >> Kevin, how is the asymmetry a problem? The HSRP linked routers >> presumably have the same routing tables, although the backup might >> have to ARP for its first packet forwarded. Even if that's an issue, >> promiscuous ARP learning shouldn't be all that much of a problem. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47273&t=47177 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
