VRF (Virtual Routing and Forwarding) allows having multiple and separated routing tables on the same system. On Linux, VRF support has been started on 4.3 kernels. Ubuntu 16.04 brings 4.4 kernels but mind that 4.
In this case, the application team is reporting a random high RTT between a client and a server. Both client and server are Linux virtual machines, under VMware vSphere, and the path is through a lot of firewalls, routers, switches, load balancers… and so on.
A not-so-easy process about QoS involves the verification of end-to-end QoS marking: are the marks maintained through the all network? Before going deep, let’s recap how an IP packet can be marked:
A very short post about 802.1x (dot1x) on Cisco Catalyst 2950 series. Configure RADIUS and enable dot1x on the switch: aaa authentication dot1x default group radius aaa accounting dot1x default start-stop group radius dot1x system-auth-control Then enable dot1x on all interfaces (additional security commands are added in the example below):
My Internet connection is cheap enough and a little bit crappy. Cisco provides Embedded Event Manager (EEM), useful to manage a situation like mine: event manager applet RESTART_ATM event interface name "ATM0" parameter input_errors_crc entry-val 3000 entry-op gt entry-val-is-increment true exit-comb or exit-val 1 exit-op le exit-val-is-increment true exit-time 5 poll-interval 3600 maxrun 10 action 1.
OpenSSH allows SSH/SFTP users to connect to the whole system by default. In many cases this is not the expected behavior: users should be relegated to the home their home directory only.
In last Cisco Live 2014 (Milan) there was a lab on Cisco VIRL/CML. Only one PC located in the Walk-in-lab room was available to start a VIRL lab, and I couldn’t miss that chance to see what exactly VIRL is.
TFTP or Trivial File Transfer Protocol is a simple file transfer protocol. TFTP uses UDP port 69, no authentication or encryption is supported, and directory navigation is not possible. Three file transfer methods are available: netascii (or ASCII for text files), octet (or image for binary files), and mail (not used anymore).
The Cisco WAAS system consists of a set of devices that work together to optimize TCP network traffic. There are two types of devices that run WAAS software: Cisco Wide Area Application Engine (WAE) Cisco Wide Area Virtualization Engine (WAVE) WAVE appliances implement virtualization: virtual blades can run one or more virtualized OSes within the WAVE appliance.
I replaced most of my Bash script with Python but sometimes I still need Bash. The following script requires uuencode and sends an email with attachments using Bash: #!/bin/bash PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin" EMAIL_OK="dainese@example.
