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VPN Client Changes Resolved Address

Posted on 2014-03-02
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Last Modified: 2014-03-12
A few users have reported that their VPN Client changes the pre-configured address from X.X.X.X to X-X-X-X.provider.net. For example - from 1.1.1.1 to 1-1-1-1.provider.net, Does anyone have any idea why would that hapen?
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Question by:Strinalena
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by:edster9999
ID: 39898575
Explain a little more.

Do you mean it changes their internet address.
So when they connect up, they get the IP 10.20.30.40 and this then shows up later as 10-20-30-40.provider.net ?
Or do you mean it changes addresses they are using - so they go to a web address of 10.20.30.40....and that changes ?

If it is there address that changes - is it their real public IP (on their home network) like 192.168.x.x that gets changed or the one they get from your VPN

...or... something totally different ?
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by:giltjr
ID: 39899429
1-1-1-1.provider.net is not an IP address, that could be a host name, but IP addresses are numbers.
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by:Strinalena
ID: 39899747
Hi,

Thanks for the replies. The issue is on the actual VPN client - When the users opens the Cisco Any Connect client - instead of them getting the normal 1.1.1.1 address in the "Connect To" Field, they get 1-1-1-1.provider.net. So the address of the Firewall to terminate the connection changes for some reason.
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by:giltjr
ID: 39899787
Still confused.  IP Addresses can not have letters in them.

Is the 1.1.1.1 your public IP address?

If they click on connect, does it work?
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Author Comment

by:Strinalena
ID: 39899941
No - the Public ip is 87.224.XXX.XXX but when the users open the VPN client (You know - when you just double-click it) - instead of it showing the above ip address - it shows 87-224-XXX-XXX.name of the provider.net. The user has been able to use the client before but for some reason - at some point it gets changed and the user starts calling the helpdesk as there is no connection via the new strange address in the VPN client. It is not happenning regularly but there have been a few cases. Does this make any sense?
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by:giltjr
ID: 39900206
It looks like something is doing a reverse lookup on the IP address of your VPN server and replacing the actual address with the name that is on the PTR record for the address.

It appears that if you have a ASA cluster setup with a specific redirection option, that can happen.

So:

Do you have a ASA cluster?

Do you have the option "redirect-fqdn enable" on your ASA cluster?

Look at the page below and search on "Enabling Redirection"


http://www.cisco.com/c/en/us/td/docs/security/asa/asa84/configuration/guide/asa_84_cli_config/vpn_params.html
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by:Strinalena
ID: 39902550
No ASA Cluster. The only comand on the device i find strange is the sysopt norpoxyarp inside. REally strange ans do not think that the issue is with the ASA but looks to me to be with the user's laptops.
So their machines are using their ISP's DNS servers and for some reason, you are saying that they are performing reverse DNS instead of forward one.
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giltjr earned 500 total points
ID: 39903033
Yes, something is deciding to do a reverse look-up and fill in the server field with the host name that is returned.

It can't do a forward lookup.  Forward look-ups take a name and see what IP address that maps to.  Reverse look-ups take an IP address and find out what name it is mapped to.

Since you know the public IP address, you can issue the command:

     nslookup x.x.x.x

Where x.x.x.x is the  IP address of the VPN server and see what is returned.  You will want to try this from inside your network and from the Internet.  

It's really not that big of a deal.
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Author Comment

by:Strinalena
ID: 39903240
I know - just annoying and it is not even our Firewall :-) Thanks for the replies
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