Tag Archives: Cisco

Cisco ASA Firewall Presents Only “ASA Temporary Self Signed Certificate”

Recently we started to get reports of untrusted certificates for AnyConnect and when accessing the ASDM web page. When you browse to the web site it was presenting the default “ASA Temporary Self Signed Certificate” rather than our public SSL certificate.

After opening a case with Cisco TAC about this they pointed us to the release notes issue in ASA 9.4(x):

Elliptic curve cryptography for SSL/TLS—When an elliptic curve-capable SSL VPN client connects to the ASA, the elliptic curve cipher suite will be negotiated, and the ASA will present the SSL VPN client with an elliptic curve certificate, even when the corresponding interface has been configured with an RSA-based trustpoint. To avoid having the ASA present a self-signed SSL certificate, the administrator needs to remove the corresponding cipher suites using the ssl cipher command. For example, for an interface configured with an RSA trustpoint, the administrator can execute the following command so that only RSA based ciphers are negotiated:

ssl cipher tlsv1.2 custom
“AES256-SHA:AES128-SHA:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:DES-CBC3-SHA:DES-CBC-SHA:RC4-SHA:RC4-MD5”

As soon as I added the command into our ASA it started working again. It sounds like this should be a default entry going forward for all ASA firewalls.

Want to learn more about elliptic curve cryptography  or look at this for a primer.

Cisco ASA Firewall 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
“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.

Slow TFTP Transfers to Cisco 3850 Switch

I recently upgraded a couple of Cisco 3850 switches and noticed that the TFTP transfer rate to get the Cisco IOS files to the switch were horrible (approximately 200Kbps) which took a LONG time to transfer the 250MB file required for these switches.  After trying a couple different TFTP clients, and finding nothing that worked, I dug into the settings on my preferred TFTPD32 software and found that changing the TFTP setting for “Use anticipation window of” to 4092 gave me about a 4x to 5x improvement in transfer speed.  Still slower than I would have liked but definitely tolerable now.

TFTPD32 Settings showing