Since a couple of months I am carrying a ProfiShark 1G always with me. It’s a small network aggregation TAP that fits into my bag (unlike almost any other TAPs or switches with SPAN functionalities). It runs solely via USB 3.0, hence no additional power supply nor network port on my laptop is required to get it running.
In this post I’ll give some hints on how to use the ProfiShark 1G with Windows (read: some initial problems I had and how to solve them) as well as some use cases out of my daily work with it.
Continue reading My Network Companion: The ProfiShark
Yes I know, ScreenOS is “End of Everything” (EoE). However, for historical reasons I am still managing many Netscreen/ScreenOS firewalls for some customers. Similar to my troubleshooting CLI commands for Palo Alto and Fortinet I am listing the most common used commands for the ScreenOS devices as a quick reference / cheat sheet. These are only the commands that are needed for deep troubleshooting sessions that cannot be done solely on the GUI.
Continue reading CLI Commands for Troubleshooting Juniper ScreenOS Firewalls
The third tool out of the DNSDiag toolkit from Babak is dnseval. “dnseval is a bulk ping utility that sends an arbitrary DNS query to a given list of DNS servers. This script is meant for comparing response times of multiple DNS servers at once”. It is not only listing the response times but also further information about the DNS responses such as the TTL and the flags. Really great for comparison and troubleshooting different DNS forwarders as well as own authoritative DNS server responses as seen by others.
Continue reading Compare & Troubleshoot DNS Servers: dnseval
I really love ping! It is easy to use and directly reveals whether the network works or not. Refer to Why Ping is no Security Flaw! (But your Friend) and Advanced Tracerouting. At least outgoing pings (from trust to untrust) should be allowed without any security concerns. However, many companies are denying these ICMP echo-requests from untrust into the DMZ which makes it difficult to test whether all servers are up and running.
I was sitting at the customer’s site replacing the DMZ firewall. Of course I wanted to know (from the outside) whether all servers are connected correctly (NAT) and whether the firewall permits the connections (policy). However, ping was not allowed. Therefore I used several layer 7 ping tools that generate HTTP, DNS, or SMTP sessions (instead of ICMP echo-requests) and revealed whether the services (and not only the servers) were running. Great!
This post shows the installation and usage of httping, dnsping, and smtpping on a Linux machine, in my case a Ubuntu server 14.04.4 LTS, as well as some Wireshark screenshots from captured sessions. Finally, a pcap file can be downloaded that shows the sample runs of all three tools.
Continue reading Advanced Ping: httping, dnsping, smtpping
This blog post is a list of common troubleshooting commands I am using on the FortiGate CLI. It is not complete nor very detailled, but provides the basic commands for troubleshooting network related issues that are not resolvable via the GUI. I am not focused on too many memory, process, kernel, etc. details. These must only be used if there are really specific problems. I am more focused on the general troubleshooting stuff. I am using it personally as a cheat sheet / quick reference and will update it from time to time.
Continue reading CLI Commands for Troubleshooting FortiGate Firewalls
When troubleshooting network and security issues on many different devices/platforms I am always missing some command options to do exactly what I want to do on the device I am currently working with. Therefore I list a few commands for the Palo Alto Networks firewalls to have a short reference / cheat sheet for myself. Maybe some other network professionals will find it useful.
However, since I am almost always using the GUI this quick reference only lists commands that are useful for the console while not present in the GUI. Continue reading CLI Commands for Troubleshooting Palo Alto Firewalls