Dual WAN question

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jadams

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So you have dual WAN's. Each are from different ISP's for redundancy.

Primary link goes down. Outgoing traffic from the LAN is pretty self explanatory. However, how does incoming traffic, specifically traffic handled by DNS, reach an internal hosted server when my operation's WAN IP has now all of a sudden change?
 
This depends on the type of WAN connection you are talking about. If you have a Dual T-1 solution with two providers who you can do BGP Peering with you then you can advertise your IP over each link and if one goes down your incoming connections will be impacted(existing sessions may drop and re establish depending on the traffic flow).

Now if you are talking a couple of business class WAN connections which wont let you BGP Peer. I supposed you could some sort of a weighted DNS record (My DNS-fu is weak so maybe someone else here can elaborate on that).
 
how fast is DNS propagated across the interwebs for everyone when a dns record is changed?
 
Varies. Some servers change in under an hour some take over a day (rare but it happens)
 
serpretetsky said:
is anycast addressing a solution to this?
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Anycast is typically accomplished using BGP. You just advertise the same subnets with different weights. That way traffic to one IP will follow a most desirable (typically shortest) route until a failover occurs and the alternate route is used. To keep it simple you can just use prepended routes.

Honestly if it was my business I'd rather have BGP failover rather than relying upon a dynamic DNS service.
 
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Dynamic DNS service completely depends on the TTL you set.

If you set it low (one minute), it will propagate in a minute once it changes.

One day propagation is a thing 10+ years in the past.

If you see a one day propagation, you either don't know what you're doing, or your ISP's recursive is shockingly broken.

Anycasting is a poor choice for this sort of situation - first you need your own ASN, and you have to convince both of your ISPs to announce it. Plus, if the link suddenly drops and you don't clear the peer, you can see a lot of traffic just disappear for more time than you're willing to lose.
 
Depending the DNS provider, some don't offer TTL's less than 30 min. Make sure you verify the minimum TTL with the provider. TTL is essentially the expiration time/date of the response to a given DNS request. So, lower TTL = more DNS traffic which is why some providers set a minimum TTL.
 
jadams said:
Is there any other way to avoid downtime?
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Yes host your information in a datacenter where they have the network solved for you???

As far as redundant WAN for local users to have a NO outage period, I can only help you with CISCO using routers or ASA in failover modes. I do not know the other vendors solutions i.e. Juniper, HP, Brocade, etc...
 
tangoseal said:
Yes host your information in a datacenter where they have the network solved for you???

As far as redundant WAN for local users to have a NO outage period, I can only help you with CISCO using routers or ASA in failover modes. I do not know the other vendors solutions i.e. Juniper, HP, Brocade, etc...
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The datacenter is a NO. Not gonna happen. EVER.

So lets discuss how to do this with Cisco ASA's and I may be able to implement a similar solution.
 
Nate7311 said:
http://www.dyndnscommunity.com/questions/21914/does-a-low-dns-ttl-affect-website-performance.html

http://www.dyndnscommunity.com/questions/7134/dyndns-and-two-wantwo-different-isp.html?sort=oldest

Take a look at these links and see if they answers some questions. In short, you'll need a DNS provider with dynamic update capability as well as a Short TTL.

Other than that, not really unless you want to do the BGP route which is much more complicated.
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I think I'm still at the mercy of everyones DNS cache, being a customer's local pc, their gateway, and any other DNS inbetween, even with short TTL's

I mean... I may just be overly paranoid. I cant remember the last time the internet actually went out to begin with. I should probably be more worried about power outages.
 
Also wouldnt a BGP route require configuration within the customer's environment? Thats not really gonna happen either.
 
You'd be at the mercy of DNS cacheing all over, yes. In theory TTL's are passed through to local DNS servers, but sometimes caching can play funky tricks.

Can I ask a dumb question? What are we trying to protect? Is it just email, or internet acces, or what?
 
Nate7311 said:
Can I ask a dumb question? What are we trying to protect? Is it just email, or internet acces, or what?
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Not a dumb question. Our hardware/software vendor is starting to get OUT of the services business and wants the partners (us) to handle it. This would require hosting web apps for customers.

Workforce Management (HR/scheduling software) which integrates nicely with our core offering of voice recording & analysis hardware/software for call centers.
 
Ahhh. I'd try a test domain and setup an account with DynDNS and use them for DNS resolution and do some testing. It'l be cheap for a throwaway domain and a month of Service from Dyn to see if that'll work for you. and see what kind of flexibility you can get.
 
that link you gave me said dyn has a ttl of 60 seconds? thats fast. I could probably live with that. I ideally i wouldnt want more than an hour or so downtime.

but like i said, im probably over paranoid about the internet.

thanks for the help.
 
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