In your scenario advertising same block over both links to your provider will not help in load sharing. Redundancy is acheived but not sharing because your ISP will receive two advertisments to the same block and BGP only chooses the best route.
You can overcome this in many ways, for example you if you have a /22 block. Devide it into 8 /24 blocks. Start advertising 4 /24s through the 1st router, advertise the remaining /24s through the 2nd router. Like this you acheived load-balance as your ISP will receive 1/2 of the routes via one link and the rest through the other. You are not done yet as this will provide load-sharing but not redundancy. For example if Link1 fails this means that 1/2 of your blocks will not be advertised and will stop receiving traffic for them. To avoid this, advertise through both routers an aggregate route for the whole /22. Like this your ISP will always use the more specific route and in a way balance the traffic over both links. When one of the links/routers fail, your ISP will use the aggregate route advertised from your other router to route all the traffic back to you. Another way, is to ask your provider to accept not just 1 route for the /24 but accept both by setting the maximum accepted routes to 2 instead to 1. 1 is the default and ISPs normally don't accept changing this default value. HTH, Yasser >From: "Ivan Yip" >Hi All, > >Thanks all your response. > >Now two routers adverise same block /24 to the isp. I found that they are >'load shared' in this sense. Only 1 link is the active for Inbound. For >example, if I download files from outside, inbound is using say link1 and >link2 is idle and no packet coming in. Some time later, I ftp again and this >time is using link2 and link1 is idle. > >Is it normal? > >TIA. misconduct and Nondisclosure violations to [EMAIL PROTECTED] ------------------------------------------------------------------------ Protect your PC - Click here for McAfee.com VirusScan Online Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=59753&t=59735 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
