Browsing articles in "Tutorial"
Apr
28
2011
How to schedule a reload
How-to-schedule-a-reload

Not everyone knows that the reload command permits to schedule a reboot system; for instance, to plan a night router restart or during a critical configuration (AAA, vty, and so on…). There are two ways to schedule a reload system: at: at a specific time/date in: after a time interval The ‘at’ keyword permits to schedule a reload of the software to take place at the specified time (using a 24-hour clock). If you specify the month and day, the reload is scheduled to take place at the specified time and date. The following example reloads the router on April […]

Apr
26
2011
IPsec VPN: EzVPN, GRE, DMVPN, VTI, GETVPN
IPsec-VPN-EzVPN-GRE-DMVPN-VTI-GETVPN

Internet Protocol Security (IPsec) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session. IPsec is an end-to-end security scheme operating in the Internet Layer of the Internet Protocol Suite. It can be used in protecting data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host). There are […]

Feb
16
2011
Decrypt type-7 password with Cisco IOS
Decrypt-type-7-password-with-Cisco-IOS

There are many tools to decrypt Cisco type-7 password, based on Vigenere algorithm. But, what can we do if we can not use these software? The Cisco-IOS method might not be new to some, but those that don’t know about it will find it useful. Suppose you would decrypt these string: username cisco password 7 0718365B000A1016141D11050A2F6527273E username fabio password 7 0110140558004B0224014600110C To find the password, you can use the Cisco Key Chain:

Feb
10
2011
How to decode G.729
how-to-decode-g-729

I have decided to write this tutorial (only for test purpose) to show how it is simple decode a G.729 stream using SPAN port, Wireshark, VoiceAge G.729 decoder and Audacity software. What is G.729? G.729 is an audio data compression algorithm for voice that compresses digital voice in packets of 10 milliseconds duration. It is officially described as Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction.

Jan
30
2011
Time-Based access lists
Time-Based-access-lists

An access list is a sequential list consisting of at least one permit statement and possibly one or more deny statements that apply to IP addresses and possibly upper-layer IP protocols. Time-based ACLs is a Cisco feature introduced in the Release 12.0.1.T to allow access control based on time. The time range, identified by a name, can be ‘absolute‘ or ‘periodic‘. Use time-based access list is easy and can be useful in some situations. To implement it, you need: Define time-range Define ACL, where the time-range is applied to Apply ACL; for istance: to the interface, to the vty, to […]

Jan
12
2011
How to trace MAC address
How-to-trace-a-MAC-address

Traceroute is a tool for measuring the route path and transit times of packets across an Internet Protocol (IP) network. Traceroute sends a sequence of Internet Control Message Protocol (ICMP) packets addressed to a destination host. Tracing the intermediate routers traversed involves control of the time-to-live (TTL) Internet Protocol parameter. Routers decrement this parameter and discard a packet when the TTL value has reached zero, returning an ICMP error message (ICMP Time Exceeded) to the sender. In a Data Center, it is often required to find a host and the layer2 path. To do it, Cisco has implemented a good […]

Dec
17
2010
Send email from your router using EEM
Send-email-from-your-router-using-EEM

Cisco IOS Embedded Event Manager (EEM) is a powerful and flexible subsystem that provides real-time network event detection and onboard automation. It gives you the ability to adapt the behavior of your network devices to align with your business needs. Customers can use EEM to create and run programs or scripts directly on a router or switch. The scripts are referred to as EEM Policies and can be programmed using a simpleCLI-based interface or using a scripting language called Tool Command Language (TCL). EEM allows customers to harness the significant intelligence within Cisco IOS Softwareto respond to real-time events, automate […]

Dec
7
2010
Access to the console via AUX port
rollover_cable

Often in a network environment, it is needed to manage a router/switch via console, but what can you do if you don’t have a computer with a serial interface? You can use another router! It is easy to do it. 1) Connect the console interface of the router/switch to the router aux interface using a rollover cable. Rollover cables essentially have one end of the cable wired exactly opposite from the other. As you can see below, this essentially “rolls over” the wires.

Nov
22
2010
Cron? no Kron :)
Cron-no-Kron

Cron is a time-based job scheduler in Unix-like computer operating systems. The name cron comes from the word “chronos”, Greek for “time”. Cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates. It is commonly used to automate system maintenance or administration, though its general-purpose nature means that it can be used for other purposes, such as connecting to the Internet and downloading email. What can I use to schedule a script or a command in Cisco? The kron feature :) Kron provides the ability to schedule some EXEC command-line interface (CLI) […]

Nov
5
2010
The break key sequence in the password recovery
The-break-key-sequence-in-the-password-recovery

What can I do if I forgot the password in my router? The fastest solution is replace it with the ‘password recovery‘ (you can try to find the password with bruteforce attack but I think it is not the better solution..). During the password recovery procedure, it is fundamental sent the correct ‘Break’ key sequence to enable ROMMON, but, as you know, the ‘break’ sequence depends by the software that you use! Below the standard break key sequence combinations for the most common operating systems.