Nov
23
2016
DDNS: How to manage a device with a dynamic public IP
ddns-how-to-manage-a-device-with-a-dynamic-public-ip-2

The DDNS aka Dynamic DNS is an old feature that several routers (non only Cisco devices) have implemented and, in some circumstances, it is very useful. DDNS is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information. It provides two mechanisms to generate or perform DDNS: the IETF standard as defined by RFC 2136 and a generic HTTP using various DNS services. In a nutshell, when this feature can simplify our lifes? When we haven’t a static IP public […]

May
31
2016
Nexus HSRP/VRRP active/active with vPC
Nexus-HSRP-active-active

In the article vPC aka Virtual PortChannel, I explained how vPC works and the benefits that it gives. However, there is another important feature using HSRP/VRRP protocols in the context of vPC: the Layer2 dual–active peer devices. What does it mean? HSRP and VRRP operate in active-active mode from data plane standpoint, as opposed to classical active/standby implementation with STP based network. From a control plane standpoint, active-standby mode still applies for HSRP/VRRP in context of vPC. A characteristic of the active HSRP/VRRP peer device is that it is the only one to respond to ARP requests for HSRP/VRRP VIP […]

Apr
20
2016
vPC aka Virtual PortChannel
vPC-aka-Virtual-PortChannel-in-deph

The vPC aka virtual Port Channel is a Cisco technology that presents both Nexus paired devices as a unique Layer 2 logical node to a third device. The third device can be a switch, server, or any other networking device that supports link aggregation technology. From a spanning tree standpoint, vPC eliminates STP blocked ports and uses all available uplink bandwidth. Spanning-Tree is used as a fail safe mechanism and does not dictate L2 path for vPC attached devices.  

Mar
20
2016
Interview with Anderson Mota Alves, 7x CCIE
Anderson-Mota-Alves-7x-CCIE

This is the first interview on Ciscozine and it is my pleasure and honor to introduce Anderson Mota Alves. With more 15 years of experience in the network consulting, he is a teacher in San Paulo university and have SEVEN CCIE!!! How do you combine study, work and personal life? During my study process combining these three things were one of the greatest difficulties I had to learn how to manage, because I had to spend so many hours of study after work and still save some time to attend to a few meetings with family and friends along the […]

Feb
1
2016
Using Cisco ISE API to write web interface
Cisco-API

In the last three months, I was involved in a project concerning the migration of the authentication system (dot1x) from Cisco ACS to Cisco ISE (1.4). At the end of this work, the account told me if it is possible to have a web interface with the active sessions, the devices authenticated via Dot1x and the devices authenticated via MAB. Reading the official guide, I found that Cisco ISE has embedded API. Cool! This what I needed!

Oct
28
2015
SecureCRT: How to import sessions via CSV file
SecureCRT-How-to-import-sessions-via-CSV-file-4

In my opinion, one of the best Telnet/Serial/SSH client is SecureCRT, that provides rock-solid terminal emulation for computing professionals, raising productivity with advanced session management and a host of ways to save time and streamline repetitive tasks. I recently had the need to import a hundred devices in SecureCRT, but I didn’t know how to do it. Surfing the web, I found a helpful python script to import it via CSV! Three components are required: SecureCRT (obviously), the script and the CSV file.

Sep
17
2015
​SYNful Knock – backdoor in Cisco devices
​SYNful-Knock-backdoor-in-Cisco-devices

Recently, Fireeye researchers have discovered a new type of malware implant in Cisco router that allows attackers to gain and keep access to these devices. The implant consists of a modified Cisco IOS image that allows the attacker to load different functional modules from the anonymity of the internet. The implant also provides unrestricted access using a secret backdoor password.

Aug
31
2015
Cisco 2015 Midyear Security Report
Cisco-2015-Midyear-Security-Report

Like every year, Cisco has released the Midyear Security Report. This paper is written to understand how attackers are evolving their techniques to evade defenses, using stealthy tactics based on agility, speed, adaptation, and even destruction. New threat intelligence and trend analysis reveal how attackers use stealthy tactics based on agility, speed, adaptation, and even destruction. During this year, adversaries continue to innovate as they slip into networks undetected and evade security measures:

Aug
20
2015
Is static port channel a good idea?
Is-static-port-channel-a-good-idea-loop

During my CCIE R&S studies (CCIE Routing and Switching v5.0 Official Cert Guide, Volume 1), I have discovered an unexpected behavior of the static port channel: a Layer2 loop! Obviously, in order for that happen, several things must happen. Suppose to have three switches:   The Ciscozine-ROOT switch, as the word suggest, is the root bridge (priority 4096); the Ciscozine-ROOT_SEC is the “backup root bridge” (priority 8192), while the Ciscozine-SW has the default priority.

Jun
27
2015
Leap Second 2015: a critical bug in NXOS
Leap-Second-2015-a-critical-bug-in-NXOS

In June 30, 2015 at 23:59:60 UTC, one minute will have 61 seconds when a leap second is added; the reason we have to add a second every now and then, is that Earth’s rotation around its own axis, is gradually slowing down, although very slowly. This will be the 26th leap second adjustment since 1972, and represents an important consideration for providers of computing, networking, and software solutions.

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