How to log everything with SecureCRT

Unlike my technical articles about configurations, protocols and so on, in this tutorial I will explain how to log automatically all SecureCRT sessions. For those that are unaware, SecureCRT is one of the best SSH/telnet client. The question is “why save everything?” In my opinion, a good approach to work with many devices (network, security, …) is to save everything (show command, configuration command and so on..). This method gives several benefits, for instance when: The telnet/SSH client buffer is full Something goes wrong You mistakenly close SecureCRT You want to check what you have done

Shellshock: a bug bigger than Heartbleed?

Recently, the Red Hat team have found a critical remotely exploitable vulnerability in the Bash (aka the GNU Bourne Again Shell), that allow a remote attacker to inject arbitrary commands. GNU Bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code via a crafted environment, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash […]

Send Cisco commands via SNMP

In the article “How to save configurations using SNMP“, I have explained how to get the Cisco configuration using SNMP. Now, I explain how to send commands via SNMP using the “ciscoConfigCopyMIB” MIB;  with this MIB, you can replace running/startup configuration, send commands, save the “show” output or reload the device. OK, let’s start :) First of all, check if your PC/Server has the SNMP suite; if not, install the net-snmp software (

How to upgrade a Cisco stack

One of the task of a good Network engineer is update the Cisco IOS to avoid bugs and to have new features; but what is the correct procedure to upgrade a Cisco stack, for instance two 2960 switches in stack? There are two main methods to upgrade the IOS: TAR image BIN image TAR image The .tar file is an archive file from which both the IOS image and the CMS files are extracted during the upgrade process. If you want to manage switches or clusters of switches through a web interface (HTML), this is the only file you need to download.

Speed up your console

Generally to upgrade/downgrade an IOS, you use the classical ftp/tftp transfer from a laptop to a router/switch; unfortunately, there are some cases where this way is not possible, so the only solution is to use the console. Suppose you have to upload an image of about 20Mb. On a 9600bps intereface, the time required to upload this image is about 35minutes (20000000/9600)! Oh my God! Fortunately Cisco permit to change the console speed using the command “speed”. By default the console interface works at 9600bps: Ciscozine#sh line console 0 Tty Line Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int […]

March 2014: nine Cisco vulnerabilities

The Cisco Product Security Incident Response Team (PSIRT) has published nine important vulnerability advisories: Cisco IOS Software SSL VPN Denial of Service Vulnerability Cisco IOS Software Session Initiation Protocol Denial of Service Vulnerability Cisco IOS Software Internet Key Exchange Version 2 Denial of Service Vulnerability Cisco IOS Software Crafted IPv6 Packet Denial of Service Vulnerability Cisco 7600 Series Route Switch Processor 720 with 10 Gigabit Ethernet Uplinks Denial of Service Vulnerability Cisco IOS Software Network Address Translation Vulnerabilities Cisco AsyncOS Software Code Execution Vulnerability Cisco Small Business Router Password Disclosure Vulnerability Multiple Vulnerabilities in Cisco Wireless LAN Controllers

February 2014: five Cisco vulnerabilities

Cisco Prime Infrastructure Command Execution Vulnerability Unauthorized Access Vulnerability in Cisco Unified SIP Phone 3905 Multiple Vulnerabilities in Cisco IPS Software  Cisco Firewall Services Module Cut-Through Proxy Denial of Service Vulnerability Cisco UCS Director Default Credentials Vulnerability

January 2014: five Cisco vulnerabilities

The Cisco Product Security Incident Response Team (PSIRT) has published five important vulnerability advisories: Cisco TelePresence ISDN Gateway D-Channel Denial of Service Vulnerability Cisco TelePresence System Software Command Execution Vulnerability Cisco TelePresence Video Communication Server SIP Denial of Service Vulnerability Multiple Vulnerabilities in Cisco Secure Access Control System Undocumented Test Interface in Cisco Small Business Devices

Dual Internet connections in active/standby mode without BGP

Suppose that your company has two independent Internet connections: the first used as main link and the second used ONLY in case of main connection fault. What can we do to avoid a ‘manual’ switch of routing and NAT tables? In general, in this case, the best solution is to use the BGP protocol with bofh providers, but this solution can be very expensive, so are there other ways to implement this process? In my opinion, one of the best solutions is to use IPSLA, PBR and the EEM features togheter, but what are these features? See you below each […]

Show interface in depth

In my opinion, a good network engineer must know the “show interface” in depth; indeed, this command is useful to obtain various interface information like drop, duplex mismatch, error, tx/rx load, … Usually, the IOS switch/router have similar “show interface” output; the differences are dictated by devices, interface and IOS. Below a show interface of a TenGigabitEthernet interface. The show is issued on a Cisco WS-C6509-E in VSS Mode with IOS version 15.