I have a single 3700 router and 2 ISP connection. One is 4 Mbps and another is 16 Mbps. I want to share the load (Not load balance) in the 1:4 ratio.
1) Is it possible ? If possible pl give some pointers
2) If not, what additional software is required to achieve load sharing. Pl give some pointers.
3) I also want to configure each link as stand by to other.
Main aim to see that both the links are utilised to maximum.
As such I havenot heard of Load-sharing on the links ..what we generally do is load-balancing either on per-destination or per-packet basis.
You are running any routing protcol to ISP or using statc or default routes. You can use your routing protocls to do equal or un-equal cost load balancing. You can also configure CEF to do per-destination or perpacket loadblalancing.
to achieve the load balancing you desire, you must use either EIGRP with ISPs which is not preferable, so that you can use EIGRPs unequal load balancing feature, to use BGP and to advertise some subnets to the first ISP ( 4mbit )that the traffic they are have equals to 4 Mbit and let all other traffic to the other ISP (16 Mbit ISP), or to use a specialised device. I personally would go with BGP solution. If you need more help regarding the solutions I described , please let me know.
With a four to one ratio of data rates, your only real choice is a load balancing appliance, and even then you will only see a four to one split as a long term average (unless your traffic is both well behaved and diverse).
Before you spend the money, you might want to reconsider your objectives. If your current loading is less than 12 Mbps, you wouldn't notice the addition of the 4 Mbps link even if you could achieve perfect load balancing. On the other hand, if your current loading is over 20 Mbps, you're overloaded with or without the 4 Mbps link. Keep in mind that if your load balancing solution sends 2 Mbps too much down the 16 Mbps link, it's no big deal, but if that 2 Mbps hits the 4 Mbps link when its already at 75% of capacity (and we've already determined that if you're not running both links at 75% or so, there was no reason to load share to begin with), the queueing delays on that link will hit the roof, even though there is capacity on the 16 Mbps link.
Alternatives to consider:
Use the 4 Mbps as emergency backup for the 16 Mbps link. You may need to use triage on the traffic and only support you critical services while in backup mode.
Dedicate the 4 Mbps to a few (static) uses that will never exceed its capacity. Depending upon your application, you may even be able to charge a premium for those users exiled to the slow link for their dedicated bandwidth.
Good luck and have fun!
Vincent C Jones