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GeezerVison is showing howdoesinternetwork.com — How does the internet work - blog about networking

How does internet work – Networking knowledge project that will tell you all you ever wanted to know about networking from a design, planning, and configuration perspective. Articles are vendor agnostic as much as possible with design solutions objectively analyzed.

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Latest – Most recent 5

  • I just passed the AWS Advanced Networking Specialty January 8, 2026
  • Cisco Champion 8th year in a row April 9, 2025
  • Google Jupiter Data Center Network Fabric – New Way of Building Data Center Network Underlay September 17, 2022
  • Cisco DNA Upgrade Issues – Application Update Stuck June 8, 2022
  • Cisco Catalyst Stack Upgrade May 8, 2022

SDDC – Software Defined Datacenters

  • New ACI deployment? Watch out when connecting APICs to Leafs
  • What is Cisco ACI?
  • CLOS Topology
  • ACI MultiPod and how to build MultiDatacenter with Cisco ACI
  • ACI MultiPod – Enable Standby APIC
  • Setting up Cisco ACI From Scratch
  • How to Advertise a Route from ACI Layer2 BD Outside the Fabric?
  • Cisco ACI – Configuring by POSTing JSON
  • Cisco ACI – API Calls vs JSON POST
  • Software-defined data center and what’s the way to do it
  • VMware TKGI – Deployment of Harbor Container Registry fails with error
  • VMware NSX-T Install Tips & Tricks
  • Google Jupiter Data Center Network Fabric – New Way of Building Data Center Network Underlay
  • NSX-T Edge Transport Node Packet Capture
  • Switch vSphere Enterprise Plus license to vSphere Standard on a NSX-T enabled cluster

Routing – How it works?

  • BFD – Sub-second Failure Detection
  • MTU and TCP MSS
  • Redistribute Static on Juniper & Cisco
  • Source-Specific Multicast Configuration
  • Unable to access Cisco ASA through AnyConnect VPN?
  • VRF – Virtual Routing and Forwarding
  • Static Route Load Balance
  • Proxy ARP
  • TCAM and CAM memory usage inside networking devices
  • Solicited-node multicast address
  • How can router decide so fast?
  • /31 subnet in point-to-point links. Is that possible?
  • BGP dampening – punishment for unstable BGP prefixes
  • Source-based routing in IPv4 and IPv6 networks
  • BGP communities
  • ICMP – Internet Control Message Protocol
  • Troubleshooting EIGRP Neighbor Relationships
  • Forwarding UDP broadcast traffic mechanisms
  • Administrative Distance for Static Route is 1 or 0?
  • Difference between defining static routes with next-hop address or exit interface
  • IPv6 RA Router Advertisement and all the flags inside
  • What is static floating route
  • PBR – Policy Based Routing using Route map
  • MPLS – Multiprotocol Label Switching
  • Administrative distance – Which route is the best?
  • Difference between Routed and Routing Protocols
  • IPv6 Anycast Address type
  • How to Advertise a Route from ACI Layer2 BD Outside the Fabric?
  • BFD – Sub-second Failure Detection
  • Redistribute Static on Juniper & Cisco
  • Unable to access Cisco ASA through AnyConnect VPN?
  • Juniper vMX Multicast Configuration
  • VRF – Virtual Routing and Forwarding
  • Static Route Load Balance
  • What is route recursion
  • TCAM and CAM memory usage inside networking devices
  • How can router decide so fast?
  • INE v5 Full-Scale Practice Lab1 TS GNS3 topology
  • INE R&Sv5 Workbook Full-Scale Practice Lab1 made in GNS3
  • BGP dampening – punishment for unstable BGP prefixes
  • Source-based routing in IPv4 and IPv6 networks
  • BGP communities
  • Troubleshooting EIGRP Neighbor Relationships
  • GNS3 topology for INE Workbook
  • Administrative Distance for Static Route is 1 or 0?
  • IPv6 RA Router Advertisement and all the flags inside
  • What is static floating route
  • Pathping more than handy network troubleshooting tool
  • BGP – Border Gateway Protocol
  • Dynamic Routing Protocols
  • Routers hardware – How are the Routers made?
  • Routing – How are routers working?
  • Routing – Static and Dynamic routes – What is route?

Switching – How it works?

  • Link Aggregation – LACP Protocol
  • WoL – Wake On LAN
  • How to Enable Dot1x – more complex setup for wired network
  • How to Enable Dot1x authentication for wired clients
  • What is a non-blocking switch?
  • HOL Head-of-line blocking
  • TCAM and CAM memory usage inside networking devices
  • VXLAN – Virtual Extensible LAN
  • What is Jitter in Networking?
  • Unidirectional communication filter between two VLANs
  • Routing between VLANs
  • Trunking Methods – VLAN Identification methods across multiple switches
  • VLANs – Trunk and Access link types
  • Static vs Dynamic VLANs
  • VLAN – What are VLANs?
  • VLAN Security – Main VLAN reason
  • VLANs controling broadcast propagation
  • Why we need VLANs, an Introduction to VLAN technology
  • PVLAN – Private VLANs

Security

  • Reflexive Access List
  • Juniper Control Plane Protection
  • QKD – How Quantum Cryptography Key Distribution Works
  • Introduction to Quantum Cryptography
  • Cryptography
  • Control Plane Protection in Cisco IOS
  • How Encryption of Network Traffic Works?
  • Mitigate DoS Attack using TCP Intercept on Cisco Router
  • How to Enable Dot1x – more complex setup for wired network
  • How to Enable Dot1x authentication for wired clients
  • What is the difference between tunnel | transport mode in IPsec
  • Source-based routing in IPv4 and IPv6 networks
  • IPv6 First-Hop Security
  • RADIUS server Infrastructure
  • Find unknown static IP on device
  • Unidirectional communication filter between two VLANs
  • How to prevent or stop DoS attacks?
  • DoS Methods – PDoS, Permanent DoS attacks
  • DoS Methods – ICMP and SYN flood, Teardrop and Low-rate DoS attacks
  • DDoS – Distributed Denial of Service attack
  • DoS and DDoS – Denial of Service attacks
  • IPSec
  • Application Layer Firewalls
  • Transparent Firewalls
  • How does Firewall defend our Network?
  • Protecting a VoIP Network with Security Appliances
  • Implement Auxiliary VLANs to make VoIP Networks secure
  • Make voice Network more secure
  • Flame Virus
  • Vishing and Toll Fraud – VoIP Vulnerability
  • Attack on SIP protocol – VoIP Vulnerability
  • VoIP spam – VoIP Vulnerability
  • VoIP Security – Main Targets of VoIP Attacks
  • Firewall – Defending Networks
  • Secure the switch – best steps
  • VACL – VLAN Access Lists
  • Switch Security Attacks – Layer 2 Security
  • VPN – What is VPN and how it works?
  • Phishing – What is phishing?
  • Configuring MACsec Encryption
  • MACSec – Media Access Control Security
  • Secure the switch – best steps
  • PVLAN – Private VLANs
  • SPAN – Switched Port Analyzer technology and configuration
  • Prevent ARP Spoofing using Dynamic ARP Inspection – DAI
  • Spoofing Attacks – ARP Spoofing
  • Prevent DHCP Server Spoofing by using DHCP snooping
  • Protecting Against STP Layer 2 Attack
  • STP Layer 2 attack – Manipulating Spanning Tree Protocol settings
  • Mitigate VLAN hopping attack – Get rid of Layer 2 attacks
  • VLAN hopping attack – Switch Spoofing and Double tagging
  • Using Port Security to Mitigate Layer 2 Attacks
  • Telnet Attacks – Ways to compromise remote connection
  • CDP Attacks – Cisco Discovery Protocol Attack
  • Spoofing Attacks – DHCP Server Spoofing
  • MAC Address Flooding – MAC address table overflow attacks
  • Switch Security Attacks – Layer 2 Security

Network Fundamentals:

  • What is route recursion
  • Proxy and Reverse Proxy Server
  • Wildcard mask – What’s the difference from subnet mask?
  • What is internet – How does the internet work and why is so important?
  • How We Open a Web Page and What is Going on Behind?
  • Network – Computer network
  • IPv6 Day – 6 June 2012.
  • Network – More news about way it works
  • VoIP and IP telephony – Defining Basics of Voice
  • Routing – How are routers working?
  • IP Address – Internet Protocol address: Basic about IPv4
  • Routing – Static and Dynamic routes – What is route?
  • LAN – Local Area Network
  • Collisions and collision detection – What are collisions in Ethernet?
  • Data Packet – IP Packet – What is this packet story all about?
  • MAC address (MAC L2 addressing) – What is this physical addressing?
  • WAN – Wide Area Network
  • What is my IP address

About Protocols:

  • BGP dampening – punishment for unstable BGP prefixes
  • Port Numbers – How does Transport layer identifies the Conversations
  • Dynamic Routing Protocols
  • OSI model – Get to know networking with 7 layer model
  • What is a protocol?
  • Voice protocols – VoIP protocols
  • PNRP Name Resolution – How it works?
  • IPSec
  • TCP and UDP port numbers – complete list

Scientific & Academic Work

  • You Know How Networks Work, Want To Know How Everything Else Works? Here’s Some Books
  • The Use of Graph Database in Network Complexity Analysis
  • QKD – How Quantum Cryptography Key Distribution Works
  • Introduction to Quantum Cryptography
  • Cryptography
  • SDN SOFTWARE DEFINED NETWORKS: AN OVERVIEW
  • COGNITIVE NETWORKS THE NETWORKS OF THE FUTURE

IPv6:

  • IPv6 Generated with EUI-64 Has a Strange Bit Inside
  • The New Way of Generating IPv6 – SLAAC EUI-64 Address Format
  • Solicited-node multicast address
  • Source-based routing in IPv4 and IPv6 networks
  • IPv6 First-Hop Security
  • IPv6 Implementation beyond theory & How playing with RA messages may be issue-istic
  • IPv6 RA Router Advertisement and all the flags inside
  • IPv6 addresses – What is IPv6?
  • IPv6 – SLAAC Stateless Address Autoconfiguration
  • IPv6 – SLAAC EUI-64 Address Format
  • NDP – Neighbor Discovery Protocol
  • What’s that % sign after ipconfig IPv6 address?
  • IPv6 Day – 6 June 2012.

Configurations:

  • Check Point Firewall VM Disk Resize
  • Create or Edit a File on Cisco IOS Flash
  • Cisco Catalyst Stack Upgrade
  • Missing good old ‘wr’ command on N9K? let’s bring it back!
  • Juniper SRX Cluster Failover Tuning
  • Reflexive Access List
  • Juniper Control Plane Protection
  • How to Clear Entire Configuration of your Juniper Device
  • Enable Source-Specific Multicast in Iperf
  • Source-Specific Multicast Configuration
  • Cisco Catalyst 6880-X VSS ISSU Upgrade Steps
  • ISSU Upgrade of Cisco Catalyst 6880-X VSS Cluster and 6800ia FEX extenders
  • TFTP via VRF
  • Control Plane Protection in Cisco IOS
  • Mitigate DoS Attack using TCP Intercept on Cisco Router
  • How to Enable Dot1x – more complex setup for wired network
  • How to Enable Dot1x authentication for wired clients
  • INE v5 Full-Scale Practice Lab1 TS GNS3 topology
  • When they throw a Cisco guy to do something with HP networking gear
  • INE R&Sv5 Workbook Full-Scale Practice Lab1 made in GNS3
  • BGP dampening – punishment for unstable BGP prefixes
  • GNS3 topology for INE Workbook
  • PBR – Policy-based Routing configuration example
  • When I connect to device with telnet or SSH I don’t see logging?
  • Saving Router Configuration to Server
  • Use TFTP to configure a Router
  • Saving VLAN.dat To NVRam
  • PVLAN configuration
  • Configuring LLDP – Link Layer Discovery Protocol
  • How to configure CDP – Cisco Discovery Protocol
  • About Cisco IOS and Juniper JUNOS
  • Command Modes – Cisco IOS – Juniper Junos
  • SPAN – Switched Port Analyzer technology and configuration
  • Basic Cisco and Juniper router Configuration
  • Creating Command Aliases – Be faster in IOS typing
  • Telnet and SSH – Remotely connect to device using Telnet and SSH
  • Mitigate VLAN hopping attack – Get rid of Layer 2 attacks
  • Automatic router backup to FTP server – How to configure?
  • Cisco Switch password recovery – Catalyst Fixed Configuration Switches
  • Protecting Against STP Layer 2 Attack
  • Manage Router’s ARP Cache
  • Using Port Security to Mitigate Layer 2 Attacks
  • Prevent DHCP Server Spoofing by using DHCP snooping
  • Prevent ARP Spoofing using Dynamic ARP Inspection – DAI

Tunneling Protocols:

  • What is the difference between tunnel | transport mode in IPsec
  • VXLAN – Virtual Extensible LAN
  • L2TP – Layer 2 Tunneling Protocol
  • VPN – What is VPN and how it works?

Network Devices and Equipment:

  • Cisco Catalyst 6880-X VSS ISSU Upgrade Steps
  • ISSU Upgrade of Cisco Catalyst 6880-X VSS Cluster and 6800ia FEX extenders
  • TFTP via VRF
  • How to generate network packets – Ostinato Packet/Traffic Generator
  • TCAM and CAM memory usage inside networking devices
  • Cisco VIRL is finally out
  • Redundant Default Gateway solutions in IPv4 networks
  • Cisco VIRL – Virtual Internet Routing Lab
  • Find unknown static IP on device
  • Router – What is a router?
  • Routers hardware – How are the Routers made?
  • VoIP Network Components
  • Switch & Hub – What are they and what is the difference?
  • Host – When the Host is Client and when Server?
  • Recovery From Corrupt or Missing Software Image on Cisco device
  • Server – What is a server and how it works?
  • NIC – Network Interface Card
  • About Cisco – What is Cisco exactly
  • About Juniper – What is Juniper exactly
  • UTP Cables – Unshielded Twisted Pair Cable
  • Optical Fiber – Fiber Optics
  • Backbone – What is backbone?
  • Network Downtime Is Expensive – Time is Money
  • Cisco EnergyWise – New way to save energy

VoIP – Voice technology:

  • What is Jitter in Networking?
  • Voice protocols – VoIP protocols
  • VoIP Network Components
  • VoIP and IP telephony – Defining Basics of Voice
  • VoIP Security – Main Targets of VoIP Attacks
  • VoIP spam – VoIP Vulnerability
  • Vishing and Toll Fraud – VoIP Vulnerability
  • Attack on SIP protocol – VoIP Vulnerability
  • Make voice Network more secure
  • Implement Auxiliary VLANs to make VoIP Networks secure
  • Protecting a VoIP Network with Security Appliances

OSI layers:

7. Application layer:

  • BGP – Border Gateway Protocol
  • DHCP – Dynamic Host Configuration Protocol
  • DNS – Domain Name System
  • FTP – File Transfer Protocol
  • Gopher
  • HTTP – Hypertext Transfer Protocol – What is HTTP Protocol used for?
  • IMAP – Internet Message Access Protocol
  • IRC – Internet Relay Chat Protocol
  • LDAP – Lightweight Directory Access Protocol
  • Netconf
  • NNTP – Network News Transfer Protocol
  • NTP – Network Time Protocol
  • PNRP the New DNS – Peer Name Resolution Protocol
  • POP – Post Office Protocol
  • RPC – Remote Procedure Call
  • RTP – Real-time Transport Protocol
  • SIP – Session Initiation Protocol
  • SMPP – Short Message Peer-to-Peer
  • SMTP – Simple Mail Transfer Protocol
  • SPDY – reducing web page load time protocol
  • SSI – Simple Sensor Interface protocol
  • XMPP – Extensible Messaging & Presence Protocol

6. Presentation layer:

  • MIME – Multipurpose Internet Mail Extensions

5. Session layer:

  • SAP – Session Announcement Protocol
  • NetBIOS

4. Transport layer:

  • Static Route Load Balance
  • Nagle’s algorithm
  • MPTCP – Multipath TCP
  • DCCP – Datagram Congestion Control Protocol
  • Port Numbers – How does Transport layer identifies the Conversations
  • UDP – User Datagram Protocol
  • TCP – Transmission Control Protocol
  • TCP and UDP port numbers – complete list

3. Network layer:

  • Static Route Load Balance
  • BGP communities
  • VXLAN – Virtual Extensible LAN
  • Redundant Default Gateway solutions in IPv4 networks
  • ICMP – Internet Control Message Protocol
  • IPv6 Anycast Address type

2. Data link layer:

  • IPv6 Generated with EUI-64 Has a Strange Bit Inside
  • Link Aggregation – LACP Protocol
  • MACSec – Media Access Control Security
  • Proxy ARP
  • L2TP – Layer 2 Tunneling Protocol
  • ISL Inter-Switch Link Protocol – Trunking or Frame Tagging protocol
  • LLDP – Link Layer Discovery Protocol
  • CDP – Cisco Discovery Protocol
  • NDP – Neighbor Discovery Protocol

1. Physical layer:

  • WoL – Wake On LAN
  • TCAM and CAM memory usage inside networking devices

 

 

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