As a network administrator I know that there are SSH fingerprints. And of course I know that I must verify the fingerprints for every new connection. ;) But I did not know that there are so many different kinds of fingerprints such as md5- or sha-hashed, represented in base64 or hex, and of course for each public key pair such as RSA, DSA, ECDSA, and Ed25519. Uh, a bit too complicated at a first glance. Hence I draw a picture.
Following is a list of the most common Cisco device configuration commands that I am using when setting up a router or switch from scratch, such as hostname, username, logging, vty access, ntp, snmp, syslog. For a router I am also listing some basic layer 3 interface commands, while for a switch I am listing STP and VTP examples as well as the interface settings for access and trunk ports.
This is not a detailed best practice list which can be used completely without thinking about it, but a list with the most common configurations from which to pick out the once required for the current scenario. Kind of a template. Of course with IPv6 and legacy IP.
While preparing for my CCNP SWITCH exam I built a laboratory with 4 switches, 3 routers and 2 workstations in order to test almost all layer 2/3 protocols that are related to network management traffic. And because “PCAP or it didn’t happen” I captured 22 of these protocols to further investigate them with Wireshark. Oh oh, I remember the good old times where I merely used unmanaged layer 2 switches. ;)
In this blogpost I am publishing the captured pcap file with all of these 22 protocols. I am further listing 46 CHALLENGES as an exercise for the reader. Feel free to download the pcap and to test your protocol skills with Wireshark! Use the comment section below for posting your answers.
Of course I am running my lab fully dual-stacked, i.e., with IPv6 and legacy IP. On some switches the SDM template must be changed to be IPv6 capable such as sdm prefer dual-ipv4-and-ipv6 default .
If you are using a Lastline device (Manager, Engine, Sensor or Pinbox) you can reach the machine via SSH after you activated it via monitoring_user_password . However, per default this uses only a password for authentication. If you want to use the key-based authentication for this “monitoring” user account you can add the public key to the authorized_keys file for that user.
This is a small record on how to add a public key to the Lastline device. However, it is quite general since the Lastline appliance is built upon a standard Ubuntu server.
The usage of the SSHFP resource record helps admins to authenticate the SSH server before they are exposing their credentials or before a man-in-the-middle attack occurs. This is only one great extension of DNSSEC (beside DANE whose TLSA records can be used to authenticate HTTPS/SMTPS servers).
While there are some great online tools for checking the mere DNS (1, 2), the correct DNSSEC signing (3, 4), or the placement of TLSA resource records for DANE (5, 6, 7), I have not found an online SSHFP validator. That’s the idea:
This is really cool. After DNSSEC is used to sign a complete zone, SSH connections can be authenticated via checking the SSH fingerprint against the SSHFP resource record on the DNS server. With this way, administrators will never get the well-known “The authenticity of host ‘xyz’ can’t be established.” message again. Here we go:
Since a few weeks I am using Tufin SecureTrack in my lab. A product which analyzes firewall policies about their usage and their changes by administrators (and much more). Therefore, the first step is to connect the firewalls to SecureTrack in two directions: SSH from SecureTrack to the device to analyze the configuration, as well as Syslog from the device to SecureTrack to real-time monitor the policy usage.
This blog post shows the adding of the following firewalls into Tufin: Cisco ASA, Fortinet FortiGate, Juniper ScreenOS, and Palo Alto PA.
Eine der häufigsten Fragen bzw. Tipps, die ich meinen Bekannten gebe, ist: Benutzt sichere Passwörter! Am besten noch verschiedene für alle Services, also Dienste/Homepages/E-Mail/etc. im Internet und Co. Und uns ist allen klar: Das macht keiner… ;) Außer man hat einen vernünftigen Passwortspeicher den man auch flexibel und von verschiedenen Orten aus benutzen kann. In einem solchen Programm kann man alle verschiedenen Passwörter eingeben und verschlüsselt in einer Datei speichern. Das heißt, man braucht zwar ein sehr gutes (= langes & komplexes) Passwort, erspart sich aber das Merken von allen anderen Passwörtern. Sprich: Man muss sich fortan nur noch ein Passwort merken und hat dann einen sicheren Zugriff auf alle möglichen anderen Passwörter. Ich verwende den KeePass Password Safe und möchte hier eine komplette Einführung in dessen Benutzung geben.