OSPF doesn't allow you to do a unequal cost load balancing . With EIGRP , this can be achieved by using the "variance" command ( under "router eigrp" ).
The " traffic share count " value is an indicaion of how many packets would be transmitted over the various paths ( equal cost ( in which case it is 1:1 ) / unequal cost ). With the use of the " variance " command in EIGRP , the router can be made to transmit traffic in ratio proportion to the metric of the unequal cost routes. Please find below the copy-paste from the Cisco Site which gives more clarity . ------------------------------------------------------------------------ ---------------------- EIGRP puts up to four routes of equal cost in the routing table, which the router then load-balances. The type of load balancing (per packet or per destination) depends on the type of switching being done in the router. EIGRP, however, can also load-balance over unequal cost links. Note: Using max-paths, you can configure EIGRP to use up to six routes of equal cost. Let's say there are four paths to a given destination, and the metrics for these paths are: path 1: 1100 path 2: 1100 path 3: 2000 path 4: 4000 The router, by default, places traffic on both path 1 and 2. Using EIGRP, you can use the variance command to instruct the router to also place traffic on paths 3 and 4. The variance is a multiplier: traffic will be placed on any link that has a metric less than the best path multiplied by the variance. To load balance over paths 1, 2, and 3, use variance 2, because 1100 x 2 = 2200, which is greater than the metric through path 3. Similarly, to also add path 4, issue variance 4 under the router eigrp command. How does the router divide the traffic between these paths? It divides the metric through each path into the largest metric, rounds down to the nearest integer, and uses this number as the traffic share count. For this example, the traffic share counts are: for paths 1 and 2: 4000/1100 = 3 for path 3: 4000/2000 = 2 for path 4: 4000/4000 = 1 The router sends the first three packets over path 1, the next three packets over path 2, the next two packets over path 3, and the next packet over path 4. The router then restarts by sending the next three packets over path 1, and so on. Note: Even with variance configured, EIGRP will not send traffic over an unequal cost path if the reported distance is greater than the feasible distance for that particular route. ------------------------------------------------------------------------ ---------------------- Hope this clarifies . Regards, Srivathsan A -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Monday, June 23, 2003 12:37 PM To: [EMAIL PROTECTED] Subject: Traffic share count [7:71116] Hello friends, I suppose that this is an easy question, but I want to make clear it. It is about the meaning of "traffic share count" that I can see when I execute an "show ip route" command: Router#sh ip route x.x.x.x Routing entry for x.x.x.x/28 Known via "static", distance 1, metric 0 (connected) Routing Descriptor Blocks: * directly connected, via Serial5/0/0/1 Route metric is 0, traffic share count is 1 I guess It has something to do with load balancing, but I would appreciate any comments about it because even when there are several routes to the same destination I can see that the share count is 1: Routing entry for X.X.X.X/29 Known via "ospf 1000", distance 110, metric 20, type extern 2, forward metric 5 Last update from X.X.X.X on ATM0/0/0.10061, 03:52:56 ago Routing Descriptor Blocks: * Y.Y.Y.Y, from W.W.W.W, 03:52:56 ago, via ATM0/0/0.10060 Route metric is 20, traffic share count is 1 Z.Z.Z.Z, from V.V.V.V, 03:52:56 ago, via ATM0/0/0.10059 Route metric is 20, traffic share count is 1 How can this value be changed? It is always 1 and I would like why Thanks all friends Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71129&t=71116 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
