Hi There everyone!
Need some help 
Suppose you are using DDNS to support your VOIP phone system. You have two ISPs and dual WAN.
What happens if one of the ISPs goes down? Is the DDNS linked to a specific interface, exclusively, with no way for Mikrotik to update it (other than scripting, I suppose) automatically in the event one WAN goes down? Or will Mikrotik update the DDNS to point to the remaining interface?
āMyā phone system use dual carrier BGP, when one is down the same IP / DNS is reachable from the other sideā¦
Not sure what you are saying, but one could conclude you like acronyms a pimped out rapper would use ;-PP.
More precisely are you saying your VOIP provider has some special characteristics,
OR
are you saying you are using the āBGPā functionality available on the router to setup traffic flow such that the desired behavior occurs??
OR
more likely something elseā¦
If you have enabled DDNS from IP ā Cloud, that IP entry is updated to the other interface that is up at the time automatically, given that you have setup your dual-WAN failover thing correctly and routed all traffic to the available interface.
If automatic failover between the WANs is in place and it affects also own traffic of the router, Mikrotik will update their own DDNS (ācloudā) without scripting, but that the propagation time to the phones and peers will be slow - the TTL of the DDNS record is quite long and the phones/peers will not query again until it expires. And if the failed WAN doesnāt go physically down, the DDNS update itself will take long as well as the system will not notice that something has happened - the IP attached to that WAN will still be up.
A virtual router somewhere in a datacenter with tunnels to your dual-WAN router is one possible solution; a VoIP āsystemā running directly in the datacenter may be an even better one.
Is āsimpleā:
Two border gateway router that use Border Gateway Protocol.
Each router has itās own fiber connection, with different mainstream provider, each coming from different directions.
If for some reason one of the two BGP connections is not working, the IP of internal VoIP/SIP gateway is still reachable near immediately from other side.
The current calls or sessions are pratically uninterrupted, just experience some packet loss.
Okay put yourself in a lay persons shoesā¦
What the heck is a border router. In my house I have one router accepting two or three wans depending.
Do you mean that I should use two routers one for each wan connection?
If it was that essential for you to stay online, then yes, plus some additional measures too. No SPOF, everything at least doubled.
Haha, it seems the two of you are really having a private conversation in codeā¦ SPOF //////////
(SinglePointOfFailure)
No, also BGP with 2 carrier can work with one unique router, but obviously if you double anything but have only unique Border Routerā¦
A Border Router (on my case) is a Router unreachable on any way from internet (= no firewall, no NAT, no queue, etc.), because use only private IP,
that act as access to āThe Internetā where you can publish your IP. (and acts only as a conduit for packets)
Yes, on this case you do not have Public IP from internet like DHCP, PPPoE etc. , but directly you say to the world āThis is my IP pool and Iām hereā
When you have a (W+L)ISP to keep up, with businesses and families you have to guarantee the Internet to, you canāt settle for a single connection to a mainstream.
Nor can you take two connections from the same provider.
Nor do you have to take two connections that come āfrom the same sideā, that is, although they are from different suppliers, the fiber cables pass close together in the path.
They have to be two suppliers, they have to be at least two fibers,
both have to have enough bandwidth if the other breaks,
and they donāt have to go the same way, because if a fiber breaks due to accidents or work, they probably both break.
Obviously the tricks do not end there.
Still not following the logic, nor how I could apply, for example I have two providers, one cable, on fibre, two separate companiesā¦
I have dual wan failover and works fine, what is the impetus for one to change to whatever frankenstein you have created??
Ok, if someone broke the fiber cable to your home, all stop regardless that everything in your house is working perfectly forever.
For prevent that, you require TWO fiber.
BUT if the fiber come from same cable, is obvious if for some reason is cutted, both stop working.
BUT if one fiber come from Halifax, and the other from Bedford, both must be broken for stop your serviceā¦
You should also mention that all this BGP and dual carriers is not something youād get at home, so @anav doesnāt need to get excited for nothing. 
Ahā¦ yeah, I thought he just wanted to understand the conceptā¦ 
But maintain same IP can be simulated, at that point, using VPN service.
When one link is down, the other line is used to estabilish VPN and keep same Public IP.
[quote=torikelly post_id=970858 time=1670414825 user_id=203857]
My problem is solved.
[/quote]
Yes, you did it, you managed to crete the topic, whait some time, spam ome gle tv & co. in the quoted text,
I hope God punish you.
And also stole the original post (http://forum.mikrotik.com/t/ddns-and-wan-failover-dual-wan/159355/1). Bad user! 
Che memoria!!! (What a memory!!!)
measure of thumbā¦ the update occurs via the interface which your route to the WAN goes (aka ādefault routeā) or at which ācloud.mikrotik.comā and/or ācloud2.mikrotik.comā is reached.
Spammers rely on the particular behaviour of most users ā¦ accepting overquoting and NOT READING what is quoted.
Topic closed, spammer blocked.