On Mon, Jan 30, 2012 at 8:27 PM, Ann Kwok <annkwok80@gmail.com> wrote:
We discover the routes is going to ISP A only even the bandwidth 100M is full
Can we set the weight to change to ISP B to use ISP B as preference routes? Can the following configuration work?
Tuning weights and localpreference values can influence traffic that your equipment sends _to_ ISP A and ISP B. These options do not control what incoming traffic gets forwarded into your network _from_ ISP A or ISP B; you need a separate strategy for incoming bits. The config you listed should do just what the vendor documentation says it does, so I can't say it doesn't "work"; it just does nothing to help remedy the situation. That is, if you have two ISP links each 100M full duplex; and one of them is at 100% outbound usage, increasing the weight of all the other neighbor's paths assuming the set of prefixes received over BGP are the same, will mean that ISP B is the preferred next-hop for each path; which means ISP A outgoing utilization should drop to near 0, and then ISP B should be just as fully utilized as ISP A is currently. You could instead identify some specific paths that are heavy users or would carry a high percentage of the outgoing traffic, and use filters/route maps to adjust local preference of specific paths, to take outgoing load off ISP A. or increase the weight for 128.0.0.0/1 on routes received from ISP B, and allow your outgoing traffic to rest of the address space to utilize ISP A, for example. But the preferred fix for this problem would be to upgrade ISP A and ISP B links to at least double their current capacity. Weight is a vendor-specific parameter, local to your router. I would consider increasing the default local preference for ISP A first, by the way, But as long as you only have one router on which ISP A and ISP B sessions land, when you have an identical prefix from ISP A and B, the outgoing path through ISP B is to be preferred by your local router, if the path has a higher weight. " What suggest to this weight no. too? " With weights the magnitude of the numbers and the numerical difference between weights is not significant; it just matters if one path has a higher weight, or both paths have equal weight. I would suggest weights that are uniformly spaced apart and easy to remember, e.g. 100 200 300 400. When you want to add ISP C later, you will also have flexibility without re-assigning your existing weights. If this works, how is ISP B upstream connection is down?
Can it still be failover to ISP A automatically?
If it won't work, Do you have any suggestion?
Thank you for your help
-- -JH