Cisco ASA ASDM Incompatibility with Java 7 Update 51

The latest version of Java 7 Update 51 that was deployed this week breaks access to Cisco ASA firewalls running ASDM.  When you connect with the ASDM you get the following error message: “Unable to launch device manager from X.X.X.X”

“Unable to launch device manager from”

The symptoms are that the web page for the firewall will show up and display normally, but you can’t connect to the server with the ASDM launcher.  The log on the firewall shows

%ASA-6-302013: Built inbound TCP connection 112 for outside:X.X.X.X/64508 (X.X.X.X/64508) to identity:Y.Y.Y.Y/443 (Y.Y.Y.Y/443)
%ASA-6-725001: Starting SSL handshake with client outside:X.X.X.X/64508 for TLSv1 session.
%ASA-7-725010: Device supports the following 6 cipher(s).
%ASA-7-725011: Cipher[1] : RC4-SHA
%ASA-7-725011: Cipher[2] : DHE-RSA-AES128-SHA
%ASA-7-725011: Cipher[3] : DHE-RSA-AES256-SHA
%ASA-7-725011: Cipher[4] : AES128-SHA
%ASA-7-725011: Cipher[5] : AES256-SHA
%ASA-7-725011: Cipher[6] : DES-CBC3-SHA
%ASA-7-725008: SSL client outside:X.X.X.X/64508 proposes the following 8 cipher(s).
%ASA-7-725011: Cipher[1] : AES128-SHA
%ASA-7-725011: Cipher[2] : DHE-RSA-AES128-SHA
%ASA-7-725011: Cipher[3] : DHE-DSS-AES128-SHA
%ASA-7-725011: Cipher[4] : RC4-SHA
%ASA-7-725011: Cipher[5] : DES-CBC3-SHA
%ASA-7-725011: Cipher[6] : EDH-RSA-DES-CBC3-SHA
%ASA-7-725011: Cipher[7] : EDH-DSS-DES-CBC3-SHA
%ASA-7-725011: Cipher[8] : RC4-MD5
%ASA-7-725012: Device chooses cipher : RC4-SHA for the SSL session with client outside:X.X.X.X/64508
%ASA-7-725014: SSL lib error. Function: SSL3_READ_BYTES Reason: sslv3 alert certificate unknown
%ASA-6-725006: Device failed SSL handshake with client outside:X.X.X.X/64508
%ASA-6-302014: Teardown TCP connection 112 for outside:X.X.X.X/64508 to identity:Y.Y.Y.Y/443 duration 0:00:00 bytes 580 TCP Reset by appliance

Cisco has included this information in their latest release notes:

If you use Java 7 Update 51, you must upgrade ASDM to Version 7.1(5.100) or later, and you can only use the Java web start. The ASDM Launcher is not supported.

So the alternatives are to downgrade your Java on your workstation or upgrade to the latest ASDM version at this point to get the ASDM working again.

How to change the subnet mask of DHCP scope windows server

You can’t change the subnet mask of the DHCP scope directly without deleting the scope, need to delete the DHCP scope first then recreate the scope with new subnet, but this will lead to largeamount of manual work

To avoid the manual work use the below netsh command toChange the subnet mask in existing DHCP scope with the simple steps

Use the below command to export the scope configuration

Syntex:

C:\>netsh dhcp server \\”Server name” scope “scope subnet” dump>c:\dhcp.txt

Example:

C:\>netsh dhcp server \\Test01 scope 192.168.1.0 dump>c:\dhcp.txt

To change the subnet mask of the scope

Open the dhcp.txt file and change the subnet mask, dhcp.txt fileresemble the following


Changed the current scope context to 192.168.1.0 scope.

Dhcp Server 192.168.1.24 add scope 192.168.1.0 255.255.255.0 "Vlan-1" "Vlan-1"
Dhcp Server 192.168.1.24 Scope 192.168.1.0 set state 1


Edit the file and save

After this, delete the scope and run the below command to create the scope from the txt file 

C:\>netsh exec c:\dhcp.txt

This will automatically create the DHCP scope with the new subnet mask

This way you can change other configuration details along with subnet mask change, like IP range and Excluderanges