2 Internet connection into One Connection

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Apr 24th, 2007
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Dear all

Can some body help

i have a problem in our office we have 2 internet connections and we want to establish a connection like when ever one them are down so another will be up automaticly so here we want to use the CISCO 3845 Router and i need to make one connection from this router that my network always have internet if one of our satelite are down

So can somebody tell me what to do and how to configure with the high security system plz im in trouble

see atach document


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Overall Rating: 4 (6 ratings)
desai.jaideep Tue, 04/24/2007 - 01:22
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(1)Are both of these KU/C band connections going to the same remote nose, or they are connected to internet?

(2)These VTC (looks like a IP camera to me) in the diagram are to be accessed from outside or what is their purpose.

(3)What is the IP addressing schema?

Pls give the answers.



wais.farzam Tue, 04/24/2007 - 03:08
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Dear Desai.Jaideep

Yes Both KU/C Band are Connected to the internet and working 24/7

Yes VTC is for Vedio Confrencing and also accessable from outside

the ip schemaa is in progress with the ISP Provider becouse we will get 16 ip blocks for these configuration and also thanks for replying and can u give me a good discusion which configuration i should use with which kind of cisco equipment

desai.jaideep Tue, 04/24/2007 - 03:58
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I forgot to ask that both the links are from the same ISPs or different.

In your setup u have a cisco router which will cater to the inside devices like bandwidth-shapers and VCON units.

Case 1 : Same ISP

Then your majority of headache is over.

You just need to ask them to route the same IP block through both the links. The scenerio would be:

Link A WAN IP:

Link B WAN IP :


Vcon IP : Gw : (routers ethernet)

routes Link A:

Link B: 50

In this case, suppose you give live IPs on the VCON equipment, then if one link is down, the other will take over. Remember, here you do not need to change the IPs of your VCON.

As far as ISA servers are concerned, they will be doing NATing just like its being done now.

Case II : Different ISPs

Then your headache starts and the network becomes more complicated.




Ethernet ISP A

Ethernet ISP B

Then you need to do NATing in your cisco router. This in turn will invite secondary IPs on ethernet.

And for eg on VCON unit, if you are giving live iP of ISP A ( then if ISP A is down, then you need to assign the ip add which is of secondary ISP.

To avoid above, you need to do NATing along with port forwarding, so that you just need to configure that in ur router instead of keeping on changing the ip address of equipment.

There must be a way out that without changing anything, everything should work.Need to test that in my lab. Will tell u after its done.

Here are few links:





wais.farzam Tue, 04/24/2007 - 05:31
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yes mr JD the ISP is the same but the ip blocks are diffrent like



something like this but the thing is that we need to give the VTCs also the public ip address through this Giga byte uplink switch and 2 saperate network for 2 campuses one office another guest house

with some bandwidh management for users for guest house


desai.jaideep Tue, 04/24/2007 - 06:46
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If the ISP is same, then dont worry...ISP will route for both of your IP blocks.

Just make sure to convey this setup to them.

Also, in this case, you can very well assign live IPs to your VTCs.

One more thing which clicked into my mind, if u are going on for same ISP, then ask them to implement BGP. In this way your second link will not be unusable.You can do load-shring with that.Never mind if you dont want to compicate ur setup.

Pls rate all helpfull posts.



wais.farzam Wed, 04/25/2007 - 02:45
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Dear JD but can u tell me which cisco router i should use and which Switches with wich configuration on it some body told me that configure the MLPP Multi link Point to Point for this configuration


leighharrison Wed, 04/25/2007 - 02:55
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Hi there,

The easiest way to accomplish this would be to do some static load balancing out of the internet interfaces. Have a look at the following config, which presumes that your 2 internet links are gig0/0 and gig0/1 (I'm sure they're not..):-

ip route g0/0

ip route g0/1

Static routing will load balance up to 6 paths by default (it could be 4, I can't remember off the top of my head). The router will then send the data out of both the interfaces and if one of them goes down, then it will switch all data to the good interface.

Also, the load balancing is done per FLOW rather than per packet, this means that any boxes that are accessed externally will keep the conversation on the correct interface.

Let me know how it goes!



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wais.farzam Wed, 04/25/2007 - 03:09
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Dear LH

Thanks for reply the thing is that i think u have seen the diagram what i have been made and showen but the problem for me is that i have 2 internet connections and i want to make something like load balance in Cisco Router that when ever one of them are down another should be up automaticly but some body told me configure the MLPP in CISCO router Multi Link Point to Point then it will work but can u tell me whic cisco Router or Firewall, Switch i can use for this project


leighharrison Wed, 04/25/2007 - 04:02
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Hi there,

I'm not 100% sure which node you are referring to, but I do think that a 3845 is a bit too much.

The kit to get depends on what termination your internet links are. If they are adsl, then you'll need a router. If they are ethernet, then I would just buy a Cisco Catalyst 3750G-24T switch, which will also do the job of the router.

For the load balancing to the internet the switch would just need 2 default gateways pointing to the 2 different internet links, then it will make all of the decisions for you.

As for MLPP, I don't think there's any need for that!



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wais.farzam Wed, 04/25/2007 - 19:58
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Dear LH


what do u think a CISCO 3750G-24t can support these configurations what i want to do if yes then for load balancing can u tell me which Kind of server i should put into it and which services should i run

leighharrison Thu, 04/26/2007 - 00:33
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Hi there,

If the internet circuits are dropped to you via ethernet, then you can do the load balancing on the switch by simply writing 2 static routes.

If the internet circuits are dropped to you via xDSL tails, x.21, etc, then you'll need a router to convert them to ethernet.

This router will then perform the load balancing, again, by simply writing 2 static routes.

Hope that clarifies,


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