Re: RRAS ip routing and ISA
- From: bingyeo <bingyeo@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 26 Aug 2009 00:34:02 -0700
"Bill Grant" wrote:
Hi Bill
"bingyeo" <bingyeo@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:DFF9F966-AE74-4B82-A107-D09B1A1D04E1@xxxxxxxxxxxxxxxx
HiHere are a few things to consider.
This is going to be a long post with several questions so please be
patient.
I have an dual homed ISA 2006 enterprise server acting as an edge firewall
connected to internal AD network 10.10.10.x/24.
I would like to join another internal subnet, 10.10.11.x/24 to use the ISA
as a proxy server to the internet. I want to use a w2k3 server as a router
for this subnet to connect to the internet, and this server will also act
as
DNS and DHCP for the subnet as well. The new subnet should not be able to
access any resources in 10.10.10.x, only to use ISA (10.10.10.7) as a
proxy
server.
I have set up an RRAS server (ROUTER) with LAN Routing as well as DNS:
ROUTER
NIC1
IP: 10.10.10.250
MASK: 255.255.255.0
GW: 10.10.10.7 (ISA internal IP)
NIC2
IP: 10.10.11.254
MASK: 255.255.255.0
For DNS, no forward zones are created.
No static routes have been added to the ROUTER.
I have also added a persistent static route on ISA by using "route add -p
10.10.11.0
mask 255.255.255.0 10.10.10.250 metric 1"
Now, when I test with a notebook configured with a static 10.10.11.x/24
address with ROUTER (10.10.11.254) as gateway and DNS server, I am only
able
to ping the ROUTER's NICs and other 10.10.11.x hosts but not any other
10.10.10.x hosts. I am not able to connect to the internet as well.
What am I missing here?
Do I need to add static routes in the ROUTER or ISA?
Next, I realised that DHCP does not work unless I authorise it with AD.
According to technet: Although it is not recommended, you can use a
stand-alone server as a DHCP server as long as it is not on a subnet with
any
authorized DHCP servers. When a stand-alone DHCP server detects an
authorized
server on the same subnet, it automatically stops leasing IP addresses to
DHCP clients.
(http://technet.microsoft.com/en-us/library/dd145306%28WS.10%29.aspx)
I tried configuring another standalone server with IP 10.10.11.x with DHCP
but still encountered the same prompt for AD authorisation. However when I
changed this server's IP config to be updated by DHCP (10.10.10.x), DHCP
on
this server became active after its IP was updated. Is there an
explanation
for this, remember, this server is stand alone and I did not have to right
click, Authorise it.
Anyway, my problem here is that I would like the DHCP server for the
10.10.11.x subnet to be stand alone. Is there any way for me to do this?
Lastly, all of my servers and clients are connected to the same network
switch. Is there anyway for me to ensure clients from 10.10.10.x subnet
and
10.10.11.x subnet do not receive IP leases from the wrong scope or is
Vlanning required?
If I use a wireless access point of IP 10.10.11.x and get clients to
connect
to it, would it ensure that they receive only leases from the 10.10.11.x
scope? Of course, I realise that this does not solve the problem for DHCP
clients who are on wired connections.
Alright, really hope to receive some help and feedback on my queries here.
Thanks in advance.
1. You can run two subnets on one physical switch, but it is not efficient.
Although the machines are connected to the same switch, machines in one
subnet cannot communicate directly with machines in the other subnet. They
must communicate through a router. These are usually confusingly called
virtual networks.
2. You cannot really run two DHCP servers on the same switch. DHCP works on
broadcasts, so there is no way to discriminate. If a machine broadcasts a
discover message, both DHCP servers will respond and the client will accept
whichever offer it receives first.
3. You don't really need the DHCP server to be standalone. You can run both
scopes on the same DHCP server, as long as your network is configured
correctly. The router between the subnets will forward the requests to the
DHCP server.
4. Unless you can see a way to configure this using VLANs, get an additional
switch and run each subnet on its own switch.
5. I would not run DNS and/or DHCP on a machine running as a router.
6. I found your proposed routing scheme a bit strange. It seemed to be aimed
at NAT routing rather than using the proxy service in ISA. In any case this
setup would not achieve your stated aim. All machines in the new subnet
would be able to see all machines in the existing subnet and vice versa.
7. To isolate one subnet, you would need to reverse your setup. The subnet
which could access the Internet but not the second subnet would need to be
directly connected to the ISA server. The second subnet would then be
connected to this subnet with a RRAS/NAT router. This simplifies the routing
but also means that machines in subnet 1 cannot connect to machines in
subnet 2 (because they are on the public side of the NAT). The setup would
look like this.
Internet
|
ISA
10.10.10.7
|
limited subnet
10.10.10 x dg 10.10.10.7
|
10.10.10.250 dg 10.10.10.7
RRAS/NAT
10.10.11.254 dg blank
|
10.10.11.x dg 10.10.11.254
You do not need any static routes. Because of NAT, all traffic from the
10.10.11 subnet uses the NAT router's 10.10.10 IP address in the 10.10.10
subnet. All traffic is automatically routed back to the NAT router, which
delivers the traffic in the 10.10.11 subnet. I haven't tested it (an I would
not do it myself), but this setup should run even on one switch.
After configuring NAT, internet access for 11 subnet works fine, but it is
able to access 10 subnet since, like you said, traffic from 11 subnet is
passed to the NAT router and uses its 10.10.10 address in the 10.10.10
subnet.
ISA is currently joined to the domain in the 10 subnet. Would there be any
problems if the setup was reversed as you suggested in #7?
Also, is there any alternative setting on the Router which I would use to
block ping, RDP etc from 11 subnet to 10 subnet if I stick with the current
setup?
Anyone is welcome to contribute their opinions.
Thanks
Cheers
.
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