Link to home
Start Free TrialLog in
Avatar of Llarissa21
Llarissa21

asked on

Cisco ASA 5200 and ISA 2k4

Hello. Recently I have decided to purchase and add a Cisco ASA 5200 to our existing network which currently only exists of ISA 2k4 serving as both a firewall and web proxy. I am wanting to keep the ISA but have it only serve as a proxy (I have BT Webfilter installed on the ISA box) so I am definately wanting to keep the filtering product in place.  I have already started configuring the ASA firewall and will post the configuration below. Also, right now we have a flat network with no dmz for web servers, etc. I am wanting to incorporate and configure an interface on the new firewall for a DMZ to incluse 3-4 web servers as well as a couple of other Terminal servers accessible by the outside world through RDP. Right now our T1 terminates to a cisco 1720 series router. All internal hosts gateway point to the router address of 172.16.0.5. The router is configured to route all traffic to the ISA box 172.16.0.19.  Also if the config copied below looks horribly bad please don't hesitate to let me know what needs to be changed :)

Questions:

1.)  What is the most efficiant and easiest way to incorporate the new firewall while keeping the ISA box in place? What will I need to change on ISA to make it no longer serve as a firewall but only as a proxy & filtering.  Is there a wizard to change from a edge firewall to a back end? Will I just leave the clients gateway pointing to .5 (router) and then just change the internal interface of the cisco asa firewall to the old internal ip of the ISA box.. Right now we have a route command on the router (ip route 0.0.0.0 0.0.0.0 172.16.0.19) that routes all traffic to the isa box. So that is why I was thinking maybe just change the internal interfae of the cisco firewall to .19.

2.) Configuring DMZ --> Does anyone have a sample config that incorporates a DMZ so that I can see how the access-lists, and interface are set up?

3.) OWA/ActiveSync --> I have created my static entry and access-list for https. Does anything else need to be configured or added in order for OWA/ActiveSync to work properly? I am a bit confused because currently we have all the certs needed for OWA/ActiveSync residing on our ISA box itself. Where will the certs need to be now that the ISA box will not be serving as a firewall?

Here is my configuration on the ASA box thus far.

:
ASA Version 7.0(5)
!
hostname ASA
domain-name XXX
enable password
names
no dns-guard
!
interface GigabitEthernet0/0
 description outside interface - WAN
 shutdown
 nameif outside
 security-level 0
 ip address 66.xxx.xxx.xxx.xxx 255.0.0.0
!
interface GigabitEthernet0/1
 nameif INSIDE
 security-level 100
 ip address 172.16.0.19 255.255.224.0
!
interface GigabitEthernet0/2
 description DMZ
 shutdown
 security-level 10
 ip address 10.0.0.1 255.0.0.0
!
interface GigabitEthernet0/3
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Management0/0
 shutdown
 no nameif
 no security-level
 no ip address
!
passwd
ftp mode passive
clock timezone cst -6
clock summer-time CDT recurring
dns domain-lookup INSIDE
access-list inbound extended permit tcp any host 66.xxx.xxx.xxx eq smtp
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq https
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq ssh
access-list inbound extended permit udp any host 66. xxx.xxx.xxx eq dnsix
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq domain
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq pop3
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq imap4
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 135
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 3389
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 3389
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 3389
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 3389
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq 1755
access-list inbound extended permit udp any host 66. xxx.xxx.xxx eq 1755
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq https
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq https
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq https
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq https
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq ssh
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list inbound extended permit tcp any host 66. xxx.xxx.xxx eq www
access-list nonat extended permit ip 172.16.0.0 255.255.224.0 192.168.30.0255.255.255.0
access-list 101 extended permit ip 172.16.0.0 255.255.224.0 any
pager lines 24
mtu outside 1500
mtu INSIDE 1500
ip local pool vpnremote 192.168.30.1-192.168.30.100
no failover
icmp permit any outside
icmp permit any INSIDE
no asdm history enable
arp timeout 14400
global (outside) 1 interface
nat (INSIDE) 0 access-list nonat
nat (INSIDE) 1 0.0.0.0 0.0.0.0
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.115 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.6 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.56 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.57 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.31 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.15 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.44 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.40 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.11 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.46 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.61 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.62 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.63 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.47 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.75 netmask 255.255.255.255
static (INSIDE,outside) 66. xxx.xxx.xxx 172.16.0.58 netmask 255.255.255.255
access-group inbound in interface outside
route outside 0.0.0.0 0.0.0.0 66. xxx.xxx.xxx 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00
timeout mgcp-pat 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server vpn protocol radius
aaa-server vpn host 172.16.0.2
 key ciscotest
group-policy VPNClients internal
group-policy VPNClients attributes
 split-tunnel-policy tunnelspecified
 split-tunnel-network-list value 101

split-dns value 172.16.0.2
 webvpn
group-policy vpn5520 internal
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
crypto ipsec transform-set FirstSet esp-3des esp-md5-hmac
crypto dynamic-map dyn1 1 set transform-set FirstSet
crypto dynamic-map dyn1 1 set reverse-route
crypto map mymap 1 ipsec-isakmp dynamic dyn1
crypto map mymap interface outside
isakmp identity address
isakmp enable outside
isakmp policy 1 authentication pre-share
isakmp policy 1 encryption 3des
isakmp policy 1 hash md5
isakmp policy 1 group 2
isakmp policy 1 lifetime 86400
isakmp nat-traversal  20
isakmp disconnect-notify
tunnel-group Remote type ipsec-ra
tunnel-group Remote general-attributes
 address-pool vpnremote

default-group-policy VPNClients
tunnel-group Remote ipsec-attributes
 pre-shared-key *
telnet timeout 5
ssh timeout 5
console timeout 0
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map global_policy
 class inspection_default
  inspect dns maximum-length 512
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect rtsp
  inspect skinny
  inspect esmtp
  inspect sqlnet
Avatar of Keith Alabaster
Keith Alabaster
Flag of United Kingdom of Great Britain and Northern Ireland image

On the ISA side it is a reconfigure job. You will need to select the single-nic template (wizard0 from configuration - networks. Open the toolbar on the right-hand side - select single nic and this will remove the existing configuration file so make sure you backup it up (export the confog, objects and rules) before you start.

You cannot use the ISA as a back-end but only in proxy mode. If you want the box to act as a backend then it must be a firewall and proxy device. Backend and frontend are firewall templates; not proxy-only templates.

I would also recommend you remove one of the nic's also or if its a capable machine, team the two nics together. Having the second nic in place unused, even disabled, can cause some funnines to the system but teaming is fine.

Personally I would leave ISA exactly as it is and set the ASA to forward the traffic to the external NIC on the ISA. this will negate the need to change all of the certificates around, mess with the OWA/activesysnc and the like but it has to be your call. For specific help on the ASA box I'll need to hand over to one of my colleagues as ISA is my baby.

Regards
keith
Avatar of Llarissa21
Llarissa21

ASKER

Hi. Thank you for the reply. One question, suppose I did leaev the ISA exactly the way it is I am guessing that it would mean that no acl's or static routes would need to be in place on the ASA firewall? I am confused because if I did that, then what would the purpose of the firewall be besides to act as a router, routing all the traffic to the ISA box. I am guessing that would be the easiest way but then my boss would insist on my reasoning for purchasing the ASA box in the first place. Could you elaborate a bit more?  Say I went ahead and used the ISA server as a backend firewall and proxy device how would it act as firewall if I already have the ASA in place with all of the static routes, ACL's, VPN connection, etc.

Interesting question and one I would have to leave you to answer.

However.

1. You could place a switch between the ISA server and the ASA device creating your dmz environment between the two firewalls. I cannot think of a much stonger combination for maximum protection.
2. The ASA will only allow traffic through that is authorised reducing any performance impact on the ISA server and improving response to the proxy service users. ASA can act as the VPN header reducing load/performance impact even further.
3. A second line of defence; should the ASA get compromised (however unlikely as it is Cisco equipment), the 'hacker' still has another firewall to face so crafted attacks are unlikely to succeed.
4. ISA can now concentrate on the application layer filtering rather than the network layer as the ASA has that covered.
5. ISA2004 is EAL 4+ accredited making it one of only two in the world (Secure Computing's Sidewinder being the other and that is used in the Pentagon) so no-one can fire you for keeping the best product, can they?
Heartily agree with Keith's last post...  Even if you don't currently need a DMZ, you can benefit from having an additional firewall between your internal subnets & the outside world.  And as Keith says, you can let each box do what it does best, since an ASA isn't built to be a proxy, but is a *very* secure firewall & is a rock-solid VPN server.

   I'd only add that if you decide to put the ASA in front of the ISA server, I strongly encourage you to get a 2nd pool of public IPs (even if it's just a tiny /30 subnet) to put on the internal interface of the ASA, & on the external interface of the ISA.  This way, you won't need NAT on the ASA (& having 2 NAT devices is a migraine waiting to happen), just do all your NAT on the ISA.

BTW, Keith is a longtime ISA guru, who I'm sure falls asleep each night counting ISA servers instead of sheep! LOL

cheers
ASKER CERTIFIED SOLUTION
Avatar of Les Moore
Les Moore
Flag of United States of America image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
>split-tunnel-network-list value 101
>access-list 101 extended permit ip 172.16.0.0 255.255.224.0 any

Split-tunnel acls are standard and should look like this. Only define what networks the clients will talk to. You may not want to allow split-tunneling at all. Using the ISA as a proxy server, you can control what your VPN clients do on the Internet while they are connected to your network. Another added benefit of setting the ISA as a proxy only box.

access-list 101 standard permit 172.16.0.0 255.255.224.0

3.)  >Where will the certs need to be now that the ISA box will not be serving as a firewall?
It think that the certs would be on the actual OWA/Active Sync front-end server(s).

Just to finish off, on point 3 of LRMoores last post to you, this is something you will need to be sure of. Whilst you have had ISA doing the work you will have either been tunnelling the ssl to the OWA box (using ISA as a conduit simply to passthrough the traffic) or you will have been bridging.  If bridging ssl - ssl then there will be a certificate on both the ISA and the OWA box. If you have bridged from SSL - http then the certificate will only be on the OWA box.
Wow.. That is some great information from everyone. Thank you so much. How should I split the points to both lmoore and keith alabaster? I have never split points so don't know how to go about it.

A few more points....

> Right now our T1 terminates to a cisco 1720 series router. All internal hosts gateway point to the router address of 172.16.0.5. The router is configured to route all traffic to the ISA box 172.16.0.19.
This is very inefficient. Apparently the router is doing your NAT for you? How are you publishing OWA and other applications with the 1700 router doing NAT?

I am so sorry for the confusion. I meant to say that our ethernet hand off (internet) comes in and plugs in to an intel switch which the ISA box and router is also plugged in to.. So all the NATing is done on the ISA box. I have double checked this and there is indeed a network rule for internet access - NAT.

> Keep the ISA as a cache-proxy only

According to keith I need to -->  select the single-nic template (wizard0 from configuration - networks. Open the toolbar on the right-hand side - select single nic and this will remove the existing configuration file. Is this correct and all I need to do in order for the ISA to serve only as a cache-proxy only?

on Keiths last comment. We are bridging SSL and have a cert on both the ISA and OWA boxes.

Thanks again for all of your help and ideas, it is greatly appreciated.
SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
Don't hesitate to come back with specific questions. Keith's the ISA expert and I'm pretty good with the ASA so if anyone can get you going, we can...

Thanks!
Ykank you :)
Lrmoore & Keith alabaster,


Thanks again for all of your help.

Lrmoore, one question. I was going through your sample configuration for the DMZ interface and I ahve a question.

what does the statement --> static (inside,DMZ1) 172.16.0.0 172.16.0.0 netmask 255.255.224.0 ... mean? The two 172.16.0.0 subnets look strange together in the one statement. I was able to add it to my ASA with out any errors but I am just curious if that was a typo on your part or if it is correct, coudl you explain to me what it does? Thanks. If you need me to open a seperate questions I can do that. Just let me know. Thanks!
> static (inside,DMZ1) 172.16.0.0 172.16.0.0 netmask 255.255.224.0 ... mean?
No typo. This means that the resulting natted IP is the same as the original IP - same/same
This satisfys the rule that all traffic is natted between interfaces, just nat's it back to itself and basically negates the NAT.
It's just the way it's done with PIX/ASA.
There is a 'nat control' / no nat control command, but it is global. If you're natting out one interface, you have to nat out all of them.
Thanks :)