Transitioning to a hosted VoIP provider router question

We currently have about 100 phones on an on premise solution from Interactive Intelligence. The hardware and gateways are aging, and we have access to reliable fast fibre so I'm debating a move to a hosted solution (ie RingCentral) since our polycom phones are all ok there wouldn't be a big cap ex.

So now the next part, LAN infrastructure. We currently have our VoIP on cisco 3560 gigabit switches, with the voice traffic isolated by VLAN. We use a cisco ASA 5520 as our firewall/router. My plan was to use another internet connection (I currently use it as a test line), then using the ASA route the VoIP VLAN traffic out one public internet connection, and keep the data traffic flowing as is on the other public internet connection (to avoid any issues with data traffic impacting call quality). So is that doable is question 1.

Question 2. Since I won't have DNS or DHCP on that VoIP VLAN once i decommission the old servers, can the ASA provide those duties for just that VoIP VLAN?

FYI I don't really need a step by step here rather a confirmation this will work. I have SmartNet so I'll get cisco involved to actually do it.
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1. Yes, your ASA can use static routes to route traffic to your VoIP provider through a specific gateway (ISP).

2. The ASA can provide DHCP, but I don't think it can provide DNS. There is no reason why you can't use it as a DHCP server and then set the DNS server to be something else in the DHCP options. The DNS server can be on another VLAN or on the Internet. I would generally prefer a DNS server locally on another VLAN.

You can also set the ASA to forward DHCP requests to another DHCP server, so you can consolidate all DHCP and DNS on a Windows or Linux server.

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bhiebAuthor Commented:
I think I'm ok on DNS/DHCP after reviewing the config last night. My windows server has 2 NIC's one on the data subnet of and one on the voice, it is already handing out IP's to the phones locally. I may have to tweak the scope options for the gateway and dns, but I think I'm ok there.

So all i need is to route the VLAN out the correct interface on the firewall, and that should be a quick call to Cisco.
Recommendation is to only have 1 subnet interface on a Windows domain controller, especially if the subnets can't talk to each other. It sounds like may have gotten away with it here, but it's a very risky design, and it can usually be avoided by doing things like using a DHCP relay agent on the router/firewall to forward DHCP requests.
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