Best practice wise - should I let the router or the ASA handle NAT
(Overloading)?
In the most general of design best practices NAT is performed between an inside and outside network. NAT overloading is generally performed at the edge when there is limited public IP address space. You can learn more about NAT overloading, also known as Port Address Translation or PAT, in RFC 2663 (PAT is referred to as Network Address Port Translation (NAPT) in section 4.1.2).
In this particular scenario you can argue that you have two inside and outside networks and will need to perform some form of NAT on both the ASA (whether that is the NAT overloading you're using now, NAT exemption, static NAT, etc) and the Cisco Router.
I can ping the 172.16.2.2 interface but not 172.16.2.1 from a pc
connected to one of the layer 2 switches (proves intervlan routing is
working -- i have a 172.20.100.8 address on the PC). Why can't I ping
172.16.2.1 from a PC but I can from the Layer 3 Switch?
The ASA 172.16.2.2 is receiving the ICMP echo-request but does not have a route back to 172.20.100.0/27. The echo-reply is actually being forwarded to the Router 172.16.1.1 via the default route.
And most of all -- Why can't I get out to the Internet from the Layer 3 switch?
Currently your ASA and Cisco Router do not have routes to internal devices other than their connected routes.
Your ASA configuration:
route outside 0.0.0.0 0.0.0.0 172.16.1.1 1
This will provide a default route via the outside interface, but how will the ASA know how to reach subnets residing behind the Layer 3 Distribution Switch?
You'll need to add routes to the internal subnets via the inside interface using the Layer 3 Distribution Switch as the next-hop IP address.
ASA static routing example:
route inside 172.19.12.0 255.255.255.240 172.16.2.2
route inside 172.19.3.0 255.255.255.0 172.16.2.2
route inside 172.20.100.0 255.255.255.224 172.16.2.2
Further reading: ASA static routing
Your Cisco Router's configuration:
ip route 0.0.0.0 0.0.0.0 200.200.200.200
Additionally, how will your border router know how to reach subnets other than it's connected routes, and the catch all default route via the outside interface's next-hop address 200.200.200.200?
Router static routing example:
ip route 172.19.12.0 255.255.255.240 172.16.1.10
ip route 172.19.3.0 255.255.255.0 172.16.1.10
ip route 172.19.100.0 255.255.255.224 172.16.1.10
ip route 172.16.2.0 255.255.255.224 172.16.1.10
Further reading: ISR static routing
I cannot get an ip address right now from the DHCP server (Windows).
Any insight into why?
Ensure you have end-to-end IP reachability between the client(s) sending DHCP discover messages and the DHCP server.
From what I can gather from your topology and configuration, the subnets 172.19.3.0/24, 172.19.12.0/28 and 172.20.100.0/27 should have no issues connecting to each other (assuming they are configured to use their respective default gateways) from a networking perspective.
You can remove the ip helper-address syntax from the SVI 100 given that the DHCP server is on the same segment and that command is used for a DHCP server(s) that is on a different segment.
interface Vlan100
ip address 172.20.100.1 255.255.255.224
ip helper-address 172.20.100.27
EDIT: Oops, I just re-read your question and I believe you are hoping to limit who can SSH to your ASA using the "ldap-attribute-map". As far as I know, the LDAP Attribute Map feature is only used for modifying VPN access, not management access to the ASA itself. I'll leave my original answer below in case you (or anyone else) finds it helpful)
The LDAP attribute map allows you to 'override' policies that are inherited from the "default-group-policy" command in the tunnel group for this particular VPN. So in essence, what you need to do is have it so the default-group-policy allows no access, but group-policy 6 allows full access (or whatever access you desire).
Without seeing the rest of your configuration, its hard to give you exact configurations you will need, but here is an effective summary:
tunnel-group TG-SVC-VPN type remote-access
tunnel-group TG-SVC-VPN general-attributes
authentication-server-group LDAP_mybusinessda
default-group-policy GP-SVC-NO-ACCESS
tunnel-group TG-SVC-VPN webvpn-attributes
group-alias Default enable
group-policy GP-SVC-NO-ACCESS internal
group-policy GP-SVC-NO-ACCESS attributes
vpn-simultaneous-logins 0
group-policy 6 internal
group-policy 6 attributes
vpn-simultaneous-logins 1
[vpn-filter ...]
[ip pool ...]
[etc]
This will make it so that anyone that authenticates against your tunnel group is not allowed to connect... EXCEPT if they match your LDAP attribute map which overrides the "simultaneous logins" setting from 0 to 1.
Best Answer
None of your aaa commands reference your aaa-server, only Local.
Try this....you will need to reference it for each aaa auth line you want to use it for.
For WebVPN, you will need to add the the server to your tunnel-group attributes. Like the previous aaa config, the radius server will always be used if it is reachable, appending the LOCAL will still access for those users if the radius server fails.