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Cisco ASA - DMZ to LAN Communication Help

Posted on 2011-02-28
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Last Modified: 2012-05-11
Hi All,

Basically I am trying to lockdown the communications between the DMZ and the LAN but am having some issues and wondered if you could help me.

I added this Config, and basically want I wanted to achieve was only allowing server “marshal01” to talk to server “lemsip” via smtp and server “exch01” via smtp, http & https

object-group service DM_INLINE_TCP_2 tcp
port-object eq www
port-object eq https
port-object eq smtp

object-group network Private_Subnets
 network-object Private_10 255.0.0.0
 network-object Private_172 255.255.0.0
 network-object Private_192 255.255.0.0

access-list dmz_access_inside extended permit icmp any any
access-list dmz_access_inside extended permit tcp any any eq domain
access-list dmz_access_inside extended permit udp any any eq domain
access-list dmz_access_inside extended permit ip host marshal01 any
access-list dmz_access_inside extended permit tcp host marshal01 host exch01 object-group DM_INLINE_TCP_2
access-list dmz_access_inside extended permit tcp host marshal01 host lemsip eq smtp
access-list dmz_access_inside extended deny ip any object-group Private_Subnets

But now the server can get to the internet and also anything on the lan as well.

How can I prevent this getting to anything on the lan apart from what I have allowed?

Thanks

Paul
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Question by:essexboy80
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by:JFrederick29
ID: 34999428
>access-list dmz_access_inside extended permit ip host marshal01 any

This rule allows full access.  Remove it to restrict access to the other rules.  If you want it to have access to the Internet (but not the LAN), add that statement to the bottom of the ACL, under the deny to private LAN networks.
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by:essexboy80
ID: 34999659
understood and working now thanks.

just to confirm my config is now

access-list dmz_access_inside extended permit tcp host marshal01 host exch01 object-group DM_INLINE_TCP_2
access-list dmz_access_inside extended permit tcp host marshal01 host lemsip eq smtp
access-list dmz_access_inside extended deny ip any object-group Private_Subnets
access-list dmz_access_inside extended permit ip host marshal01 any

but how come the internet rule works when it is below the deny?
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Expert Comment

by:JFrederick29
ID: 34999682
Because you are only denying the server to the "Private_Subnets" networks and not the Internet.

if you denied "ip any any" then Internet would not work.
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by:essexboy80
ID: 35149204
All Sorted thanks guys
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JFrederick29 earned 500 total points
ID: 35149677
Glad to hear.  Can you accept an answer.
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