2 ISPs, 2 WANs, combine bandwidth?

Unanswered Question
Aug 2nd, 2010

Hey people out there,
Hope I get some advise of interconnecting experts, but not bias suggestions on my "concept".
Correct me *politely* if I'm wrong.

Firstly, let's call ISP A (ADSL) and ISP B (Hybrid Fiber Coaxial).

Secondly, a slash (/) would usually mean downstream speed/upstream speed (i.e. 15Mbps/1Mbps)

I currently have a Broadband Subscription with ISP A with 15Mbps/1Mbps only.
But however I need 6Mbps and above for web hosting, etc.
I hope I'm not obliged to answer why I need so much bandwidth for.

I've terminated the service from ISP B because apparently they blocked port 80 (I know I can use DynDNS redirection, etc. but I don't want my users to type additional wordings i.e. :81, another disadvantage is also because new users wouldn't type additional wordings behind the address, in this case they'll getting time out) and few other reasons such as technical support.

But right now, I need to think I'll need to take up the subsciption from ISP B because of bandwidth issues.

So my decision is:
Take up ISP B's service plan on top of ISP A's service plan, but however, there'll be problem I'm going to encounter (stated below).

Advantage on ISP A:
Can use port 80

Disadvantage on ISP A:
Only 1Mbps upstream

Advantage on ISP B:
Up to 10Mbps (I've tried hosting, users get up to 9Mbps most of the time, locally (SGP), and up to 6Mbps and sometimes 8Mbps on US and Europe)

Disadvantage on ISP B:
Port 80 blocked

My aim:

  • Use ISP A's Port 80 functionality
  • Use ISP B's 10Mbps upstream

Problems that I might encounter:

  • How can I use "load-balancing" and "port-redirection on a Cisco Switch or Router (?) (if i'm not wrong(?), studied CCNA but can't really remember)
  • Which IP will be shown if it is possible?

Is it possible?


I have this problem too.
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Eric Boadu Mon, 08/02/2010 - 13:50

Find out why ISP B blocks port 80 to your specific web hosting address. Are you going over your bandwidth limit? If so, please buy more bandwidth from your ISP B and let them know that port 80 is necessary for your business. Not sure what type of devices on your end but router/firewall will do the trick. Use Policy Based Routing to identify HTTP traffic from inside and send it over the ISP B connection. ISP B = Egress and ISP A = ingress

Thx, Eric

Curtis1993 Mon, 08/02/2010 - 22:37

Hi there, thank you for replying.

But do take note that I'm not an Enterprise user, but Home user which means both my ISPs subscriptions are for normal residential users for an example, like Comcast/AT&T.

Therefore it's normal for ISP B to block port 80, am I correct?

Do correct me if I'm wrong.



jean.moncada Mon, 08/02/2010 - 22:53

Yes its normal to block port 80 for home isp's , and you can't do bgp either in that situation, you will also not be able to serve requests from one isp and send it out another isp in your type of situation. simply because the client initiated a tcp session with a particular ip address which is in the destination ip header, any replies back to the client using a different isp will use a different ip address (not requested no session established etc) and the client request will just time out.

You can always upgrade to business internet plan

jean.moncada Mon, 08/02/2010 - 19:23

first find out why they block port 80, If they give you a good answer or are not willing to do it, maybe you can configure a bgp multihomed setup with the two isps. First you will need to get a BGP AS# from ARIN, And let the ISP's know you want to setup a bgp multihomed setup with them

then configure bgp where as you setup two route-maps for ISP B, one for outgoing traffic with as-path prepend and a route-map for incoming traffic with a higher preference. below are the bgp commands needed to set up the route maps under router bgp (please note I left out a couple of important bgp commands and just writing down the config commands that pertain to accomplishing the requested goal when using bgp. If you wish to use the bgp solution, just let me know and I'll provide you with a complete config depending on the bgp agreement you have with both your ISP's

router bgp 65001 ##assuming 65001 is the AS provided to you by ARIN.net

neighbor a.a.a.a remote-as 65002     ##assuming ISP-A is using as 65002

neighbor b.b.b.b remote-as 65003     ##assuming ISP-B is using as 65003

neighbor a.a.a.a route-map ISP-A-IN in

neighbot a.a.a.a route-map ISP-A-OUT out

route-map ISP-A-IN permit 10

set as-path prepend 65001 65001 65001    ## This ensures that incoming traffic from the internet goes through ISP B which allows port 80 in your case.

route-map ISP-A-OUT permit 10

set local-preference-110   ## This ensures that outgoing traffic goes through ISP A which has more bandwidth in your case.

I feel the above is an option you can use to help you resolve your specific problem. but if i was you I would just call the isp up and see why 80 is not allowed and just switch isp's if anything..

Curtis1993 Mon, 08/02/2010 - 22:42

Hi there,

What I've forgotten to mention is, I'm using a normal HFC Cable Modem and normal ADSL Modem for consumer, not enterprise CSU/DSU.

Hope you do get what I meant, so I guess it's not possible to inform both ISPs that I would want to combine bandwidth, etc.

Because if I do, I'll have to pay business price for the services, but I'm the only person managing the servers, etc. that's why I'm on residential subscriptions.

Hope you understand

Eric Boadu Tue, 08/03/2010 - 07:28

Yeah without business plan you will not succeed just pay it and let them know that you are running SOHO entrepreneur business at home. Otherwise this forum assume you are enterprise business and looking to spend high $$$ for your business need. Thx, Eric

Curtis1993 Mon, 08/02/2010 - 23:04

I see... But what if let's say I just want to make use of the bandwidth from ISP B, but sending back the requests from the original designated ISP, which in this case, ISP A?

jean.moncada Mon, 08/02/2010 - 23:15

Hold on when you asked

" But what if let's say I just want to make use of the bandwidth from ISP B, but sending back the requests from the original designated ISP, which in this case, ISP A?"

do you mean you just serve webrequests via ISP A, but you use ISP B for just surfing the net and other services, then you can. What you can't do is have web requests come in ISP A and have them answered back out through ISP B or vice versa when using home residential service.

Curtis1993 Mon, 08/02/2010 - 23:53

Hmm, yes you got it partially right - I want to serve web requests using ISP A, but since there's not enough bandwidth, can I combine ISP A and ISP B's bandwidth but serve back the requests using ISP A, purely just making use of ISP B's bandwidth, not to use it to reply web requests.


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