Connecting the world…

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Cisco ASA NPE image

I got complains from a customer who wasn’t able to configure 3DES or AES encryption for a VPN tunnel. Sounds familiar with a problem I had a couple of weeks ago. So I gave the customer the advice to upgrade and activate the VPN-3DES-AES feature. He tried but that didn’t solve this problem.

I remotely logged in and checked the software he was using. I noticed he was using the image asa832-npe-k8.bin. Problem found!!!

NPE stands for No Payload Encryption. For export to some countries, payload encryption cannot be enabled on the Cisco ASA 5500 series. For version 8.3(2), you can now install a No Payload Encryption image (asa832-npe-k8.bin).

Features that are disabled in the No Payload Encryption image include:

  • Unified Communications;
  • Strong encryption for VPN (DES encryption is still available for VPN);
  • VPN load balancing (note that the CLI is still present; the feature will not function, however)
  • Downloading of the dynamic database for the Botnet Traffic Filer (Static black and whitelists are still supported. Note that the CLI is still present; the feature will not function, however);
  • Management protocols requiring strong encryption, including SSL, SSHv2, and SNMPv3. You can, however, use SSL or SNMPv3 using base encryption (DES). Also, SSHv1 and SNMPv1 and v2 are still available;

If you attempt to install a Strong Encryption (3DES/AES) license, you see the following warning:

WARNING: Strong encryption types have been disabled in this image; the VPN-3DES-AES license option has been ignored.

I replaced the software image with the regular image and the problem was solved.

Cisco ASA: web interface not working

I had to troubleshoot a Cisco ASA today, where the client wasn’t able to connect to the management web interface anymore via https. The customer didn’t install ASDM locally, but always starts the Java-based version.

After upgrading the Cisco ASA to software version 8.2(1) and a reboot, the client wasn’t able to connect to the web interface anymore. I was able to connect to the firewall with my locally installed ASDM client, but I couldn’t access the web interface either.

While troubleshooting I first tried the basic settings, like management access-list, regenerate crypto keys and change the management port. All these options didn’t help, but the strange thing was that the web interface was working remotely.

While working with Mozilla I received the following error:

cannot communicate securely with peer: no common encryption algorithm(s).

In Google Chrome I receive the following error:

Error 113 (net::ERR_SSL_VERSION_OR_CIPHER_MISMATCH): Unknown error.

And of course Internet Explorer didn’t gave any usable information. I started looking at the supported encryption algorithms within the firewall with a show version. I noticed that VPN-3DES-AES was disabled. The next step was the enable the VPN-3DES-AES ciphers. The upgrade license for this feature is available for free at http://www.cisco.com/go/license.

I activated the VPN-3DES-AES feature, but still wasn’t able to connect to the firewall with the web interface. I checked the SSL encryption used by the firewall.

fw01# show ssl
Accept connections using SSLv2, SSLv3 or TLSv1 and negotiate to SSLv3 or TLSv1
Start connections using SSLv3 and negotiate to SSLv3 or TLSv1
Enabled cipher order: des-sha1
Disabled ciphers: 3des-sha1 rc4-md5 rc4-sha1 aes128-sha1 aes256-sha1 null-sha1
No SSL trust-points configured
Certificate authentication is not enabled

The firewall still didn’t enable the ciphers supported in my browser. If the VPN-3DES-AES license isn’t installed, only the cipher des-sha1 is enabled by default. I added the correct ciphers with the following command:

fw01(config)# ssl encryption aes256-sha1 aes128-sha1 3des-sha1

After adding the command I was able to connect to the ASA with both the web interface and the ASDM.

Another NVRAM broken?

On Monday I visited another customer who had problems saving the running configuration of a Cisco devices. The devices involved were a Cisco 2620 and a Cisco 2610XM router. Both routers weren’t able to save their running configuration.

Both routers show the following error-message:

startup-config file open failed (Bad file number)

By both routers I was able to look at the contents of the flash memory, but I wasn’t able to look at the contents of the NVRAM. When trying to look at the contents of NVRAM, you receive the following error-message:

Directory of nvram:/

%Error opening nvram:/ (Bad file number)

No space information available

22w0d: %SYS-4-NV_BLOCK_INITFAIL: Unable to initialize the geometry of nvram

The following information can be found on the error-message on the Cisco website:

%SYS-4-NV_BLOCK_INITFAIL : Unable to initialize the geometry of nvram

 

Explanation    The software has detected that it failed to initialize the NVRAM block geometry (a part of the NVRAM that hosts non-configuration data files). Typically, these files are used by SNMP to store and retrieve non-configuration persistent data across a system reload. This condition may occur when the entire NVRAM is packed with the configuration, and the newer version of software that supports this feature could not find enough room in the NVRAM to initialize the block file system.

Recommended Action    Reduce the configurations in the NVRAM by at least 2Kb.

Source

Luckily one of the two routers was the old production router, which was swapped and the customer thought the NVRAM was broken. So I could use that router for testing purposes.

I started looking at the some physical aspects of both routers. They both had the following hardware specifications:

  • 16 MB Flash memory
  • 64 MB RAM memory
  • 32K NVRAM
  • IOS version 12.4(5)

While looking at the running configuration of the active router, I noticed that the running configuration was almost 2900 bytes (29K), which is stored in NVRAM. I believed that the error-messages were generated because NVRAM was full. I started deleting some configuration from the broken router, until the running configuration was only 20K. But I still wasn’t able to save the running configuration.

The last change I had was updating the IOS. I downloaded the last Main Release, which is 12.4(23). I formatted the flash memory and uploaded the image to the spare router. And fortunately, after a reload, I was able to save the running configuration.

The running configuration was still almost 2900 bytes. I issues the command to compress the configuration:

service compress-config

Now the running configuration is compressed from almost 2900 bytes to 1000 bytes.