ifconfig.it

Where the vNIC meets the Network

Welcome Hugo

Ladies and gentlemen, welcome to my new website! I mean site url, content and topics are still the same but but now I use Hugo instead of Wordpress. Why change Speed: my website got slower and slower. Static pages are fast, very fast. Easy of use: I started to use markdown to write posts then copy&paste them in Wordpress via browser. This process was slow and required too many steps.

Cisco ASA boot problem

Cisco ASA memory problem ASA doesn’t boot: Launching BootLoader... Default configuration file contains 1 entry. Searching / for images to boot. Loading /asa825-k8.bin... Booting... Press ESC to interrupt boot: Use BREAK or ESC to interrupt boot. Use SPACE to begin boot immediately. We’re now in rommon: rommon #0> Check variables: rommon #3> set ROMMON Variable Settings: ADDRESS=0.0.0.0 SERVER=0.0.0.0 GATEWAY=0.0.0.0 PORT=Ethernet0/0 VLAN=untagged IMAGE= CONFIG= LINKTIMEOUT=20 PKTTIMEOUT=4 RETRY=20 Config network parameters.

Cisco ASA and Office 365

Office 365 is widely used between many customers. Some of them happen to manage all the Internet connections through a Cisco ASA, not the fancy ASA-X with Firepower, just the plain old 5510. I was asked to allow Office 365 traffic, looks easy huh? Step 1: know your enemy After some Google-fu I found Microsoft kindly provides an update list of the IP/subnet/URLs necessary to access various services including Office 365, Lync, OneNOte etc.

Cisco WLC roaming troubleshooting scripts

As it often happens, everything begins with a call from a customer with a problem. The problem is related to WiFi roaming in a warehouse with clients disconnecting from RDP sessions. The clients are industrial PCs installed on forklifts that move quite fast (and dangerously). Second rule of troubleshooting: measure As the first rule is clearly identify the problem, I skip to the second one. How can we measure roaming problems?

WiFi security 4 dummies

Customer site, their security policy for WiFi is an SSID with a secret PSK: the IT manager type the password on my PC to allow me to access the network. Maybe he’s not aware of my keylogger or that the password con be easily retrieved in cleartext. Let’s see how. Windows 10: retrieve the WiFi PSK in cleartext Show a list of all WiFi profiles configured on the PC:

Drop and bogons list on Cisco router

The Cyberspace a.k.a. the Internet is full of bad guys wanting to mess with our computers right? Of course everyone of us have a firewall configured with proper access and inspection rules, don’t ya? Spamhaus and Team Cymru can help providing list of known bad IPs and subnets that should be filtered in our networks. Spamhaus DROP list “DROP (Don’t Route Or Peer) and EDROP are advisory “drop all traffic” lists, consisting of netblocks that are “hijacked” or leased by professional spam or cyber-crime operations (used for dissemination of malware, trojan downloaders, botnet controllers).

OED tools: tmux

The need If you work with Linux machines and you don’t use a terminal multiplexer you’re doing it wrong. What is a terminal multiplexer? It lets you switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal. The Solution I use tmux, some people prefer sceen, just pick one and learn how to use is. For tmux users this cheat sheet helps.

OED tools: bash oneliners

Linux scripting is a skill every network/system engineer should learn in the early stages of the career. Plenty of guides available in the interwebz, The Bash Academy is a good start. A particular type of scripts are the one-liners: just a line of code to solve a problem. This is the latest I’ve used while testing autossh, check active ssh sessions continuously: while true; do netstat -an | egrep -e ':22 '; sleep 2s;clear;done Enjoy!

OED tools: OneNote

The Problem Notes, code and configuration snippets, links, screenshots… where/how to save them and allow and easy/fast way to tag/search them when needed? The Solution In my opinion the best software for notes is Onenote today. One note has a better integration with Windows 10, it’s free, supports multiple platforms and the mobile App actually works. Among all the cool features maybe my favourite is to be able to search text inside the pictures pasted inside a note.

Cisco Live 2016 Europe

Hi CLEUR! This year, for the fourth year in a row, I’ve attended Cisco Live Europe. I’ve earned the “Netvet” status, that means my name was on the wall before the keynote, ain’t that great? ;-) Aesthetics apart, this year’s event was the biggest I’ve attended so far, twelve thousands people in a huge venue (for European standards) and a lot of sessions available. Here’s my recap of the event.