Category Archives: Network


DNS stands for Domain Name System Types of DNS servers: Authoritative server – The server has authoritative information about the queried domain and it will respond the request with the information in its local database. Not configured as a recursive resolver – The server will respond with a DNS Referral Response message to inform the client where… Read More »

Riverbed WAN Optimization

Introduction: WAN Optimization are useful on a high latency links (>200ms?). 60-90% data Steelhead devices are setup in-path. WAN Optimization techniques Compression at the TCP packet level Scalable Data Referencing – Data is stored on the local Steelhead with a pointer. If the remote Riverbed sees a block of data that has already been sent, it send… Read More »


MTU – Maximum transmission unit PMTUD – Path MTU Discovery Links have a maximum packet size limitation depending on the protocol/technology. MTU defines the maximum bytes of a packet on a link. With PMTUD, endpoints are capable of determine the MTU of a path. When a endpoint sends a packet larger than the MTU, this is fragmented on… Read More »


Routing Protocols Distance-Vector Protocols: RIPv1, RIPv2, IGRP, EIGRP Based on Bellman–Ford algorithm, Ford–Fulkerson algorithm or DUAL FSM A node inform to the neighbors about the topology changes. Each node doesn’t have knowledge of the entire path to a destination. They know about the direction and the distance to its destination. Less computational complexity and message overhead. Best route… Read More »

Cisco Wireless

Compatibility Matrix Deployment modes: Converged access Centralized (or local) FlexConnect     Converged Access Converged Access requires a WLC 5760 / 5508 + 3850 Catalyst switches or a combination of 3850 switches Converged access components: Mobility Controller – Mobility management tasks and systemwide coordination tasks. Mobility Agent – keeps the wireless client database and handle authentication. Provides access point connectivity and CAPWAP… Read More »


This is a Cisco proprietary technology used for encrypting data across networks that require full mesh connectivity. Traditional VPN topologies are hub and spoke. Components: Key server – Centrally manages encryption keys. Not part of the encryption. Dedicated router. Group Member – Routers that will encrypt the data GDOI protocol – Group Domain of Interpretation. Modified version of… Read More »

Domain Name

    Whois Protocol to obtain information about a domain name. It uses TCP port 43 telnet 43 – search for the ?? – provides help There are two server modes: Thick – Stores all the data of the domain although it’s not the authoritative WHOIS Thin – Stores minimum data of… Read More »


Two modes: Multi mode – 200m maximum for 10GB and 500m for 1GB Single mode – from 500m to 50Km Cisco SFP are different part numbers depending on the fiber mode   Connectors LC – Lucent Connector SC – Subscriber Connector   Don’t mix fiber optic with fibre-channel. Fibre-channel is a transport protocol, initially designed to go over… Read More »

Spanning Tree

Types of spanning tree: CST – Common Spanning Tree – 802.1q RSTP – Rapid Spanning Tree – 802.1w PVST – Per Vlan Spanning Tree – Creates one instance per VLAN and STP is run for each VLAN. MST – Multiple Spanning Tree – 802.1s – It’s possible to define the number of instances and which VLANs belong… Read More »

Cisco IOS router configuration

  !! LOGGING !! Adds the time in the logs and debug entries in miliseconds service timestamps debug datetime msec service timestamps log datetime msec !! To test service sequence-numbers !! VRF DECLARATION !! VRF NAME can be any string to identify the VRF !! rd – route distinguisher with the format <ASN>:<number> or <IP… Read More »