transitioning voice and data service

al4629740 used Ask the Experts™
We are about to upgrade our voice and data system.

They just brought an OptEman and we will have fiber services available to us.  The question I have is that what changes will need my attention for our network.

I have the DHCP server on our LAN and DNS server on our LAN.  We have port forwarding setup on the firewall which belongs to our service provider.  The only thing that I see that I need to worry during this transition is the port forwarding.

Are there any other things you experts can think of that I should be asking?

We currently have a T1 line which will be upgraded.  We also currently have VoIP

We also have two separate domains, that we are thinking about consolidating, which we will do at this time.  Our email server operates on a separate domain than from our current network domain.
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Heres one (hard earned) suggestion:
Before switching your systems over to the new service, I would strongly suggest that you test the new connection to confirm the ISP is not blocking any of the inbound ports you need.  They will deny they block any ports, but dont belive them: test it anyway, in both directions.
gt2847cSr. Security Consultant
Is the external address space you are using changing?  Unless you have a direct address allocation, this will likely come from your ISP.  If your address space is changing and you are offering any external services you will need to make sure your DNS gets updated in a timely fashion.  Services would include Email (MX records if you host your own email), Web (CNAME or A records if you host your own web servers).  If you're doing a hot cut from your old service provider, you'll need to coordinate DNS changes so that you are not "off the air" for an extended period of time.  When preparing for a transition that includes IP address changes, you will want to lower the time to live (TTL) values for your critical DNS records to some small value (30 minutes or so) prior to your change.  48 hours is the common default TTL for most records, so you'll need to do your changes several days prior to the cut-over.


Where would I change the TTL values?  Is this in the Windows Domain/DNS Server?
gt2847cSr. Security Consultant
Do you host your own externally facing DNS?  If so, it would be on that/those systems.  If your external DNS is hosted (like Network Solutions, GoDaddy, DynDNS, etc), it would be through their tools.  There are default TTLs for the DNS server as well as per record TTLs.  Some solutions also allow per zone defaults.  It will just depend on what is seving your external DNS as to how easy it will be to modify.
Reid PalmeiraTelecom Engineer
Top Expert 2005
I'll second the DNS checks on any kind of public facing. if you're runningg your own servers, that's doubly importing for things like MX records and making sure the new public IP block you're assigned isn't on mailing blacklists.

Also if you're running VoIP, check with your ISP and VoIP provider for any kind of QOS that might need to be setup on the new WAN link. Additionally for VoIP, if you're setup like a hosted VoIP environment confirm whether or not you need to worry about far-end NAT traversal or you may run into situations where inbound calls from the PSTN to your phones fail while outbound calls are fine. If you're setup with something like a SIP Trunk going to an IP PBX check to see if your VoIP provider has that SIP Trunk setup by static IP address, in which case you'll want to let them know the new public IP to use to setup that SIP Trunk.

If the ISP is replacing the WAN router you shouldn't have to verify physical interfaces (T1, Ethernet) but you may also want to make sure whatever you have connected to that WAN router (firewalls, proxies, etc.) have necessary interfaces and / or config options to run in parallel while you test out the new connection. And if they don't then you'll want to setup a plan to be able to swing services back quickly to minimize service interruptions if there are any isues with the new ISP connection.

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