05-15-2002 06:55 AM - edited 02-20-2020 10:03 PM
I am trying to find a way to have multiple hosts inside a DMZ be able to access my entire internal network. Does anyone know of a way to do this without creating individual statics for every device that may be accessed?
05-15-2002 09:20 AM
If you have only one DMZ it is very easy with access list, you have to just do following, assuming you want to permit all the dmz and inside hosts to go anywhere (Including internet) freely:
------------------------------------------------------------
access-list acl_inside permit ip any any
access-list acl_dmz permit ip any any
access-group acl_inside in interface inside
access-group acl_dmz in interface dmz
------------------------------------------------------------
But if have multiple DMZs (say 4) and you want only specific hosts on inside/dmz to access specific hosts/services then you have to be a little more specific. In the config below we assume that you have 4 dmzs :
------------------------------------------------------------
nameif ethernet0 outside security0
nameif ethernet1 inside security100
nameif ethernet2 dmz1 security90
nameif ethernet3 dmz2 security80
nameif ethernet4 dmz3 security70
nameif ethernet5 dmz4 security60
ip address outside xx.xx.xx.xx1 255.255.255.224
ip address inside 172.16.0.1 255.255.255.0
ip address dmz1 172.16.1.1 255.255.255.0
ip address dmz2 172.16.2.1 255.255.255.0
ip address dmz3 172.16.3.1 255.255.255.0
ip address dmz4 172.16.4.1 255.255.255.0
access-list acl_outside permit
access-list acl_inside deny tcp any any eq 6667
access-list acl_inside deny udp any any eq 6667
access-list acl_inside permit ip any any
access-list acl_dmz1 deny tcp any any eq 6667
access-list acl_dmz1 deny udp any any eq 6667
access-list acl_dmz1 permit ip any 172.16.1.0 255.255.255.0 172.16.0.0 255.255.255.0
access-list acl_dmz1 permit ip any 172.16.1.0 255.255.255.0 172.16.3.0 255.255.255.0
access-list acl_dmz1 deny ip any 172.16.1.0 255.255.255.0 172.16.2.0 255.255.255.0
access-list acl_dmz1 deny ip any 172.16.1.0 255.255.255.0 172.16.4.0 255.255.255.0
access-list acl_dmz1 permit ip any any
access-list acl_dmz2 deny tcp any any eq 6667
access-list acl_dmz2 deny udp any any eq 6667
access-list acl_dmz2 deny ip any 172.16.2.0 255.255.255.0 172.16.0.0 255.255.255.0
access-list acl_dmz2 deny ip any 172.16.2.0 255.255.255.0 172.16.1.0 255.255.255.0
access-list acl_dmz2 deny ip any 172.16.2.0 255.255.255.0 172.16.3.0 255.255.255.0
access-list acl_dmz2 deny ip any 172.16.2.0 255.255.255.0 172.16.4.0 255.255.255.0
access-list acl_dmz2 permit ip any any
access-list acl_dmz3 deny tcp any any eq 6667
access-list acl_dmz3 deny udp any any eq 6667
access-list acl_dmz3 deny ip any 172.16.3.0 255.255.255.0 172.16.0.0 255.255.255.0
access-list acl_dmz3 deny ip any 172.16.3.0 255.255.255.0 172.16.1.0 255.255.255.0
access-list acl_dmz3 deny ip any 172.16.3.0 255.255.255.0 172.16.2.0 255.255.255.0
access-list acl_dmz3 deny ip any 172.16.3.0 255.255.255.0 172.16.4.0 255.255.255.0
access-list acl_dmz3 permit ip any any
access-list acl_dmz4 deny tcp any any eq 6667
access-list acl_dmz4 deny udp any any eq 6667
access-list acl_dmz4 deny ip any 172.16.4.0 255.255.255.0 172.16.0.0 255.255.255.0
access-list acl_dmz4 deny ip any 172.16.4.0 255.255.255.0 172.16.1.0 255.255.255.0
access-list acl_dmz4 deny ip any 172.16.4.0 255.255.255.0 172.16.2.0 255.255.255.0
access-list acl_dmz4 deny ip any 172.16.4.0 255.255.255.0 172.16.3.0 255.255.255.0
access-list acl_dmz4 permit ip any any
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
nat (dmz1) 1 0.0.0.0 0.0.0.0 0 0
nat (dmz2) 1 0.0.0.0 0.0.0.0 0 0
nat (dmz3) 1 0.0.0.0 0.0.0.0 0 0
nat (dmz4) 1 0.0.0.0 0.0.0.0 0 0
access-group acl_outside in interface outside
access-group acl_inside in interface inside
access-group acl_dmz1 in interface dmz1
access-group acl_dmz2 in interface dmz2
access-group acl_dmz3 in interface dmz3
access-group acl_dmz4 in interface dmz4
static (inside,outside) xx.xx.xx.xx2 172.16.0.100 netmask 255.255.255.255 0 0
-----------------------------------------------------------------
In the above example:
1. we have restricted all the hosts on all the interface from accessing IRC on the internet but have allowed all other internet services to be accessed.
2. All the hosts on the inside are free to access any host on any interface.
3. All dmz1 hosts are allowed to access all inside, dmz3 and internet (except IRC:6667) but they can't access hosts on dmz2 and dmz4.
4. Hosts on dmz2,3,4 can access only internet (except IRC:6667).
Hope this will help you.
05-15-2002 10:31 AM
So if you are using an access-list you can connect directly to hosts on your internal network by their real (not NATed) IP address? I thought you had to do statics to go from a less trusted (dmz) to a more trusted (inside) network.
05-15-2002 12:00 PM
I am sorry, I forgot to include two very important config entries. After putting this DMZ hosts can access inside hots with their real IP address and you don't have to put any "static (inside,dmz1)" statement
-------------------------------------------
access-list acl_no_nat permit ip 172.16.1.0 255.255.255.0 172.16.0.0 255.255.255.0
nat (dmz1) 0 access-list acl_no_nat
-------------------------------------------
05-16-2002 03:58 AM
Great...thanks for the help.
05-16-2002 04:30 AM
Hi,
really to permit a traffic from less secure area to a more secure area you must
use a static command, if you don't want to nat the address you can use a static of this type (the nat 0 version for the static):
static (inside, dmz1) 1 72.16.1.0 255.255.255.0.0 172.16.1.0 255.255.255.0
with the nat 0 command you cannot initiate connection from the dmz1 zone.
bye,
Graz.
05-16-2002 10:54 AM
Hi,
With "nat 0" you don't need any static to access from dmz1 to inside and with tying it to access-list there is no problem in initiating a session from dmz1. I have this configuration working.
bye
mk
05-17-2002 02:15 AM
Hi,
I agree...
with the access-list in the nat 0 command is right!
bye
Graz.
05-16-2002 08:45 AM
When you create your static reference the entire inside network address.
My inside network is 172.16.20.0 and my dmz is using public addresses.
I am using the following:
static(inside,dmz1) 172.16.20.0 172.16.20.0 netmask 255.255.255.0 0 0
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