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Networking

NetFlow 102 – FNF – Flexible NetFlow

Netflow configuration is different by platform and IOS version. Initially, Cisco IOS supported what is now known as “Traditional/Original Netflow(TNF)”, but newer versions of the IOS support “Flexible Netflow (FNF). Support for Traditional Netflow configuration is being dropped from neweer IOS versions, so if available, use Flexible Netflow configuration on …

DMVPN

1. DMVPN DMVPN – Dynamic Multipoint VPN is a technology that uses IPSec, mGRE and NHRP to provide a dynamic VPN infrastructure. DMVPN evolved in several phases as follows: DMVPN phase 1: Hub and Spoke – spokes only communicate via Hub DMVPN phase 2: Hub and spoke with spoke to …

How CEF works

1. Process Switching 1.1 How it works Network interface detects a new packet on the wire. The interface will receive the packet and will place it in the I/O memory. It will then send a “receive interrupt” to the processor to indicate that a new packet needs to be switched. …

MPLS L3 VPN

This article assumes the “provider” network already has an IGP in place and that the LDP is configured to advertise label bindings between LSRs. Check MPLS 101 on how to do that. 1. Verify LDP is working within provider network One common mistake when configuring L3 MPLS VPN appears when …

IS-IS Mechanics – CLNP

1. ISO OSI Terminology ISO OSI term TCP/IP Equivalent End System Host Intermediate System Router Circuit Interface Area Area Domain Autonomous System IS-IS = Intermediate System to Intermediate System CLNP = Connection-Less Network Protocol = Layer 3 network protocol that is used to communicate between ESes. CLNP offers a CLNS …

IS-IS 101

1. Starting the routing process Starting IS-IS process requires a 2 step configuration: 1. In the global config 2. On the interfaces that will be enabled for IS-IS 1.2 Passive interface The passive interface command in IS-IS has a basically an opposite meaning to what it means in the other …

Cisco Enterprise Architecture

1. Hierarchical Model Cisco Enterprise Architecture is based on a hierarchical model that consists of: Access Layer: provides connectivity without compromising network integrity Distribution Layer controls access to resources that are available in the core efficient Bandwidth usage implementation of QoS policies (policy-based traffic control) Core Layer (aka Backbone) optimize communication …

IPSec VPN 101

1. IPSec IPSec is a framework of open standars that offers security services to IP communication. When using IPSec you get the following benefits: Data confidentiality – packets are encrypted before being sent Data integrity – the receiver can verify if a packet was altered between the sender and itself …

PfR 101 – Perfromance Routing

1. PfR Technology PfR stands for Performance Routing, but the feature was first called OER (Optimized Edge Routing). This is why most commands still start with the oer keyword. The idea behind PfR is to have a controlling entity (Master Controller) that takes over routing decisions for one or more …

NSF – Non Stop Forwarding

1. What is NSF NSF is a feature that allows routers to keep on forwarding traffic (non stop forwarding) even in the event of a restart. This is done by separating the control and the data plane, having one process involved in building the routing table and another process in …