topic Firewall DNS in Network Security

Firewall DNS

wasiimcisco — Tue, 12 Mar 2019 00:53:10 GMT

Hi,

I have Wireless Client (172.31.250.x) in corpx segment (Secuirty 91) which are trying to access the webmail which is published over the internet. Email Server is

located inside segment (security 100) on IP address (192.168.251.137). Clients are able to browse Internet fine but emails and Internal Applications are not working

because Public DNS is resolving the PUbic IP addresses of these applications.

I want my Wireless Client to access these Internal IP addresses and want to configure the firewall for this DNS issue.

Current configuration for the email Server is this

access-list acl-out extended permit tcp any host xx.210.84.37 eq https

static (inside,outside) xx.210.84.37 192.168.251.137 netmask 255.255.255.255

static (inside,corpx) xx.210.84.37 192.168.251.137 netmask 255.255.255.255

nat (inside) 1 0.0.0.0 0.0.0.0

nat (corpx) 1 0.0.0.0 0.0.0.0

global (corpx) 1 interface

global (inside) 1 interface

There is no access-list on the corpx interface.

Kindly assist what I am missing. I want the email server to be available for the wireless cients as well as Internet and users over the Internet.

Re: Firewall DNS

Karsten Iwen — Mon, 28 Jan 2013 12:18:04 GMT

You need DNS-doctoring:

static (inside,outside) xx.210.84.37 192.168.251.137 netmask 255.255.255.255 dns

What's that rule for:

static (inside,corpx) xx.210.84.37 192.168.251.137 netmask 255.255.255.255

Do you really need that?

--
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Firewall DNS

wasiimcisco — Tue, 29 Jan 2013 03:36:20 GMT

Hi,

I tried the above command but no luck.

static (inside,outside) xx.210.84.37 192.168.251.137 netmask 255.255.255.255 dns

I have even removed the below mention commnad though the below command was DNS docotoring so that once the request hit on corpx interface it will redirect to inside interface towards the private IP address of exchange.

But both the options are not working.

Kindly assist.

Re: Firewall DNS

Karsten Iwen — Tue, 29 Jan 2013 06:45:05 GMT

did you clear the DNS caches on your PC?

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