back-up conection to internet

Posted on 2000-04-25
Last Modified: 2010-09-30
is it possible to have 2 network range addresses at two different isp (with different access methods to internet, two satellites or something like that), but the internet users can access the servers from my organization with the same fully qualified domain name, in case that one connection or another fails?

is it another possibility to have a total back up connection to internet?

Question by:adriancristea
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Accepted Solution

hstiles earned 75 total points
ID: 2750901
You would be unlucky if your ISP experienced a loss of service across their entire infrastructure...

As an example, we use a piece of equipment made by Ericsson, called a Colorado.  It supports both leased line a single standard rate ISDN connection.

You could set up a multilink route so that if the leased line was to go down, the device would automatically dial an ISDN number to reach the outside world.

Author Comment

ID: 2753969
i'm still waiting for an answer with two different isp. from my knowledge it's not possible, but i hope that there is a solution.


Expert Comment

ID: 2933002

in fact there is 1 full solution and 1 partial solution.
The full solution is that you obtain your own AS number and interface via BGP.4 to two different ISP's. This is called multihoming and is also what ISPs are using to interconnect.

The partial solution only works for incoming and outgoing email and web browsing. It does not work for access to your corporate web server. It goes as follows : you buy two routers and configure them to use VRRP (virtual router redundancy protocol), cisco's implementation is called HSRP. You connect the ethernet interface of each router to your lan and the serial interface to 2 different ISPs. In case of failure of one of the routers or the ISP's leased line your outgoing traffic will use the backup router. So web browsing and outgoing mail will always work. Incoming mail now. Incoming mail is always sent to the ip address of the server that is mentionned in your DNS zonefile as being an MX server. one can put each MX record more that one MX records with a different weight, e.g. : 10 MX 20 MX has an IP address of your first ISP, has an IP address of your backup ISP, but in reality for you this is the same physical machine in your LAN. In this case all mail will be sent to via your first ISP. If connectivity via the first ISP is lost, mail will be sent to

I hope this answers your question,

Kind regards,


P.S. I would be interested to understand whether other options are also possible.
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Author Comment

ID: 2937294
the full solution is what i need. thank you very much.


Author Comment

ID: 2937309
to jordi: how can i give you some points (i don't have much:400)?

Expert Comment

ID: 2942460
adrian, i am happy with the 7 points as mentionned for this question. Info in obtaining your own AS number can be found at if you are in Europe.

Author Comment

ID: 2944241
i think they are 70 points. but anyway, i don't know how. i'll reload the question; you just answer (no matter what) and i'll give you the points.

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