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two broadband connections

Posted on 2010-08-24
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Last Modified: 2012-06-21
user has two modems attached to a Sonicwall TZ 180W. One is a DSL with five static IP address. The other is a cable modem with a dynamic ip. Right now I have the Sonicwall using the cable modem as the main internet connection because it is much faster. The DSL is just there for failover.

The DSL is also being used for its static IP address. A domain name is associated with that IP for remote access to the server and for email.

The DSL modem went out yesterday and the user was unable to contact his email or remote into the server.

The server is running Microsoft SBS 2003.

I would like him to be able to still access it if either one of the connections go down.

I recommended getting a static to dynamic IP address through NoIP or another service. Is this the best option and would this work well, or is there another, better option?
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Question by:mrmyth
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by:Philonator
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Not sure if this is possible:  On the firewall page can you create priority rules for the failover?  

Something like this:
-allow email traffic cable
-allow internet traffic cable
-allow email traffic dsl
-allow internet traffic dsl

The logic is that, when the cable modem fails, the dsl will take over.  The only kicker with this is that you would have to put email through the cable modem and you would have to have some type of bandwith balancing on your sbs.
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jorlando66 earned 100 total points
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Check to see if the cable provider has a static IP option.  you can use a service like dyndns.org but I do not know how MX and RDNS would be handled if you did.
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by:Philonator
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My comment won't work- mx records are bound to an IP.
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by:bryon44035v3
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you indicated you already have static ip addresses, keep them - on both internet connections

the way you want to do it is create additional A records, and a secondary MX record.

if you currently have:
mx = mail.you.com
A = mail.you.com = 1.2.3.4

then you could have:
mx priority 0 = mail.you.com
mx priority 10 = mail2.you.com
A = mail.you.com = 1.2.3.4
A = mail2.you.com = 5.6.7.8 (the other internet connection)

for the other hostnames like remote.you.com:
remote.you.com = 1.2.3.4 , 5.6.7.8

so if one fails, the client would presumably try the next one
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by:aoakeley
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You need a DNS failover service such as http://www.dnsmadeeasy.com/index.html

This allows for dynamic switching of external DNS records when connections go up and dowm.
eg. remote.domain.com points to the DSL connection.
     -- DSL connecton goes down
        -- DNS automatically changes to the Cable connection

As long as you have the correct ports forwarded etc the user never (hardly) notices.
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by:scraane
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If you CANT get a static IP address on your cable modem, then yes, you could use the NO-IP service.

Setup your MX records:

 10 ip_address_to_DSL_or_DSL_hostname
 20 no-ip_address_that_points_to_your_cable
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by:jorlando66
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bryon44035v3:The cable modem had dynamic IP not static.
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by:aoakeley
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You can still use DNS failover with a dynamic IP so the user only has to remember one dns name to connect to. Just use DynDns on the cable modem connection and a CNAME in the failover that points to the DynDns name.

Just to be clear there are two issues here
- primary and secondary MX (that's the easy one)
- same DNS name pointing to whichever is the primary connection and failing over to the secondary connection so external remote user only have one dns name to remember.
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by:mrmyth
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Thanks for the posts. I called the cable provider and they won't give static IPs at this location, just to clarify.
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by:squigit
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Its worth pointing out that the 'real' way of handling this is to use something like BGP to have the same block of IPs available via either network connection, but that's probobly not something that your ISPs would be willing to work with you, given that you can't a a static Ip from one of them.  Other way to handle this is to have the SBS server (or just email services) hosted - they'll have a much better uptime than you'll be able to get from a small office setup.
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by:mrmyth
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Thanks for all the help. I think I'm going to just wait and see how the one fixed IP connection does. If it's stable now and doesn't fail, then I'll just leave it. Otherwise I will recommend hosted Exchange or the No-IP option.
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