Accessing Internet through two ISPs

5 pts.
We have a 512 kbps link Internet connection from an ISP say ISP1. We are connected to the Internet through a DLINK DI-804HV router and a DLINK DFL-300 Firewall. Now we want to enhance our speed from 512 kbps to 1 Mbps. But instead of enhancing the same link, we are planning to get another 512 kbps link from another ISP say ISP2 so that both will be redundant to each other. As the existing Router and Firewall each have single WAN port, we are planning to upgrade to Cisco Devices with at least two WAN ports each. Suppose, in our Cisco router, S0 port connects ISP1 with Default Gateway address and S1 port connects ISP2 with Default Gateway address My ethernet side address is 192.168.1.x and connected to a switch. I write two static routes (default routes) 1. #ip route 0 2. #ip route 0 So there are two default routes, both having administrative distance as 0. My question is 1. Will the routing occur through both the ISP Defult Gateways? 2. Will both the bandwidths be summed up to 1 mbps (512 kbps + 512 kbps). Please tell my planning is ok or you suggest some thing different. Thanx for your help.

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Actually, if you’re using D-Link class devices (SOHO), and you want increased bandwidth through multiple links, I’d recommend the Linksys RV-042/082/etc. series.

That allows you to use the two Internet feeds either for load balancing, or failover.

The only problems I’ve encountered (and I think it was Yahoo’s fault) is that one time we had FTP connections broken because of “suspected PASV port theft”. This was caused by a single FTP connection being spanned across two IP addresses, and only occurred for about a month.

Overall though, I’d say to do it that way. I’ve done a couple of different installs with those routers and have been quite happy with the results.


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  • Ams753
    Thanx Bob for your suggestion. I think, that is the solution. With Linksys 042/082, the purpose can be solved. It will help load balancing as well as take care of failover. But Cisco being such a flexible router, why can't we use it for the same? Is there any other config.. in Cisco routers to solve this problem? May be my idea was wrong. But I want to know the reason. Can you please explain, why it does not work? If the administrative distance for both the links are same i.e 0, why all the requests by different users are not splited up in two links. Requests going through ISP1's gateway should get reply through ISP1 and requests going through ISP2's gateway should get reply through ISP2.
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  • Gmatteson
    What you can do is enable CEF (cisco express forwarding) as a switching path on your router(s). This will allow you to load balance on a per-packet or per-destination case. If you set two default routes ip route s0 ip route s1 by default the cisco IOS will load balance across equal cost routes (up to four routes). The default load sharing method for this is per-destination because the IOS is process-switched unless CEF is turned on. This will allow you to have a aggregate in/out-bound throughput of 1mbps. If you are hosting any services that are bound soley to an ip address associated with either ISP the only solution for load-balancing inbound services is either DNS, or a BGP autonomous system number in which you would have to exchange BGP with your ISP.
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  • Bobkberg
    The simple answer is because using routing preferences has no mechanism to be aware of a load to share. Routing preferences are fine when you're talking about failover. I believe (but haven't had time to experiment) that the higher Cisco routers CAN be made to do this, just not with routing tables. If you register with cisco and get a cco ID, you can browse their configuration examples and other on-line materials (and download it). You just won't be able to get any software. It's free. The load balancing mechanism in the Linksys routers basically takes an ongoing look at how much traffic each of the links is carrying and makes a decision as to which link is less busy for the new connection to use. Much as a NAT/PAT router keeps track of which private IP on the inside is connected to which public IP on the outside, the load balancing mechanism keeps track of who inside is using which outbound line, and how much. I hope that helps, Bob p.s. Partially related to your private question, this is useful for all people asking for help, but NOT a reflection on you. Many times, there are questions from people which go unanswered. Here are some of the reasons: - The question is poorly worded and gives us little or no clue as to what is actually being asked. - The question is directed to the wrong group (People whose area of expertise lies elsewhere) - The question requires serious research, and being volunteers, few of us have the time to do research that the person asking should have done on their own. - The question looks very much like a homework assignment from school. We do not like doing student's homework for them, especially since they may show up on our doorstep looking for a job someday, and we'd like to know that they can do their own work. Bob
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  • Ams753
    Hi Bob, Thanx for your explanation. Could you please tell me if this will work. In my router, NAT will be configured. Half of the private IP addresses will be translated to i.e. IP address of WAN port connecting to ISP1 and the rest will be translated to i.e. IP address of WAN port connecting to ISP2. So this arrangement will load balance as well as redundant. ams753
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