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Cisco PIX 515 - Restrict Access from DMZ to Internal Network

Posted on 2006-05-04
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Last Modified: 2013-11-16
We have a Cisco 515 with inside, outside and DMZ interfaces.  We had trouble opening up our DMZ to the outside world but alas this has been resolved.  Our current issue is more significant because we believe that access from our DMZ to the internal network is NOT restricted.  It's our understanding that we should not be able to access our internal network from the DMZ as this is going from an interface with a lower security to one with higher security.  However, I noticed this morning that when logging on to the server on the DMZ I am receiving a login script.  Furthermore, I am able to browse to computers on our internal network.  I'm sure it's something to do with our access rules, so here's a copy of our config:

Building configuration...
: Saved
:
PIX Version 6.3(4)
interface ethernet0 auto
interface ethernet1 auto
interface ethernet2 auto
nameif ethernet0 outside security0
nameif ethernet1 inside security100
nameif ethernet2 DMZ security50
enable password 61xYgpu4KcM8ihNr encrypted
passwd 61xYgpu4KcM8ihNr encrypted
hostname TEST
domain-name TEST.LOCAL
clock timezone EST -5
clock summer-time EDT recurring
fixup protocol dns maximum-length 512
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
name 10.10.1.21 GPSVR
name 10.10.215.0 ny2_net
name 10.10.1.0 ny1_net
name 10.10.210.0 nc1_net
name 10.10.100.0 ny1_dmz_net
name AAA.AAA.199.90 ny1_ext_ip
name BBB.BBB.33.10 ny2_ext_ip
name 10.10.235.0 ca1_net
name CCC.CCC.10.22 nc1_ext_ip
name DDD.DDD.210.2 ca1_ext_ip
name AAA.AAA.199.91 DMZ
name 10.10.100.50 DMZSVR
access-list inside_outbound_nat0_acl permit ip any ny1_net 255.255.255.0
access-list inside_outbound_nat0_acl permit ip host GPSVR host 10.10.200.211
access-list inside_outbound_nat0_acl permit ip ny1_net 255.255.255.0 nc1_net 255.255.255.0
access-list inside_outbound_nat0_acl permit ip ny1_net 255.255.255.0 ca1_net 255.255.255.0
access-list inside_outbound_nat0_acl permit ip ny1_net 255.255.255.0 ny2_net 255.255.255.0
access-list inside_outbound_nat0_acl permit ip ny1_net 255.255.255.0 ny1_dmz_net 255.255.255.0
access-list outside_cryptomap_dyn_20 permit ip any ny1_net 255.255.255.0

access-list outside_access_in permit icmp any any echo-reply
access-list outside_access_in permit icmp any any unreachable
access-list outside_access_in permit icmp any any time-exceeded
access-list outside_access_in deny tcp host 10.10.1.235 ny1_net 255.255.255.0
access-list outside_access_in deny tcp host 10.10.1.240 ny1_net 255.255.255.0
access-list outside_access_in deny ip host 10.10.1.235 ny1_net 255.255.255.0
access-list outside_access_in deny ip host 10.10.1.240 ny1_net 255.255.255.0
access-list outside_access_in permit tcp host 10.10.1.235 host GPSVR
access-list outside_access_in permit tcp host 10.10.1.240 host GPSVR
access-list outside_access_in permit ip host 10.10.1.235 host GPSVR
access-list outside_access_in permit ip host 10.10.1.240 host GPSVR

access-list outside_access_in permit tcp any host DMZ eq www
access-list outside_access_in permit tcp any host DMZ eq ftp
access-list outside_access_dmz permit tcp any any
access-list outside_access_dmz permit udp any any

access-list ny2 permit ip ny1_net 255.255.255.0 ny2_net 255.255.255.0
access-list dmz_access_in permit tcp host DMZSVR host 10.10.1.20 eq netbios-ssn
access-list dmz_access_in permit udp host DMZSVR host 10.10.1.20 eq domain
access-list dmz_access_in permit udp host DMZSVR host 10.10.1.20 eq netbios-ns
access-list dmz_access_in permit tcp host DMZSVR host GPSVR eq 1433
access-list outside_cryptomap_40 permit ip ny1_net 255.255.255.0 ny2_net 255.255.255.0
pager lines 24
mtu outside 1500
mtu inside 1500
mtu DMZ 1500
ip address outside ny1_ext_ip 255.255.255.0
ip address inside 10.10.1.254 255.255.255.0
ip address DMZ 10.10.100.1 255.255.255.0
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Question by:callis610
3 Comments
 
LVL 17

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by:Dushan De Silva
ID: 16611230
An example may help - here's a Cisco PIX one with a mail server running on the DMZ -

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a008015efa9.shtml

BR Dushan
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LVL 9

Accepted Solution

by:
stressedout2004 earned 1000 total points
ID: 16611748
So your requirement is for inside to be able to access the DMZ, but DMZ should not be able to access "any" host
on the inside segment. Correct?

If that is your requirement, then you need to take this static out:

static (inside,DMZ) 10.10.0.0 10.10.0.0 netmask 255.255.0.0 0 0

Although, you didn't post your entire config, I know about the static line because I helped you out with the outside access to the DMZ.
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Author Comment

by:callis610
ID: 16641267
stressedout2004 you did me good once again.  sorry it took me so long to get back and award the points.  your help was greatly appreciated, thanks!!!
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