Filed under Networking


1. What is a wireless local loop? In a telephone network, a wireless local loop (WLL) is a generic term for an access system that uses a wireless link to connect subscribers to their local exchange in place of conventional copper cable. Using a wireless link shortens the construction period and also reduces installation and … Continue reading

Ethernet Private Line

Ethernet Private Line (EPL) and Ethernet Virtual Private Line (EVPL) are Carrier Ethernet data services defined by the Metro Ethernet Forum. EPL provides a point-to-point Ethernet virtual connection (EVC) between a pair of dedicated user–network interfaces (UNIs), with a high degree of transparency. EVPL provides a point-to-point or Point-to-Multipoint connection between a pair of UNIs. The services are categorized as an E-Line service type, with an expectation … Continue reading


AMS-IX is a distributed exchange, currently present at multiple independent colocation facilities in Amsterdam. Each site is equipped with one or more access devices to enable connections to the AMS-IX infrastructure. Colocation services for connected networks are available at all data centre facilities, these are not part of the AMS-IX services. The current implementation of the AMS-IX … Continue reading

Network traffic measurement

In computer networks, network traffic measurement is the process of measuring the amount and type of traffic on a particular network. This is especially important with regard to effective bandwidth management. Network performance could be measured using either active or passive techniques. Active techniques (e.g. Iperf) are more intrusive but are arguably more accurate. Passive techniques are of less network … Continue reading

Layer 2 Vs. Layer 3 Networks

LAYER 2 NETWORKS A switch works with MAC addresses at layer 2 of the OSI 7 layer model. Devices used on a Layer 2 Ethernet network include network interface cards, hubs, bridges and switches. Ethernet devices use ‘burned in’ MAC addresses to identify each host. These addresses are attached to network interface cards and cannot … Continue reading

What’s VPLS

Cisco says it as: Virtual Private LAN Services (VPLS) is a class of VPN that supports the connection of multiple sites in a single bridged domain over a managed IP/MPLS network. VPLS presents an Ethernet interface to customers, simplifying the LAN/WAN boundary for Service Providers and customers, and enabling rapid and flexible service provisioning, because … Continue reading

What does “arp who-has tell” means?

05:47:34.050566 arp who-has tell yyy.yyy.yyy.yyy Basically this means that yyy.yyy.yyy.yyy has data to send to but don’t know the MAC address associated to it, so it’s trying to update the ARP table cache. For geeks who want to understand thoroughly, check links below: RFC826 ARP by Wireshark ARP

SFP module (Small form-factor pluggable transceiver )

The small form-factor pluggable (SFP) is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA). It interfaces a network device motherboard (for a switch, router, media converter or similar device) to a fiber optic or copper networking cable. It … Continue reading

WCCP (Web Cache Communication Protocol)

Web Cache Communication Protocol (WCCP) is a content-routing protocol that provides a mechanism to redirect traffic flows in real-time. It has built-in load balancing, scaling, fault tolerance, and service-assurance (failsafe) mechanisms. The Web Cache Communication Protocol (WCCP) is a Cisco-developed protocol that allows certain Cisco routers and switches to transparently redirect traffic to a cache … Continue reading

How to Check for Dropped Packets

Open the “Start” menu and type “Command prompt” into the search bar. If you are on Windows Vista or newer, simply wait for the “Command prompt” menu item to appear or, if you are on Windows XP or older, click the “Search” button and allow the computer to seek out the file. Run the “Command … Continue reading

What’s ISAKMP (Internet Security Association and Key Management Protocol)

ISAKMP is a protocol for establishing Security Associations (SA) and cryptographic keys in an Internet environment. ISAKMP defines the procedures for authenticating a communicating peer, creation and management of Security Associations, key generation techniques, and threat mitigation (e.g. denial of service and replay attacks). As a framework,[1] ISAKMP is typically utilized by IKE for key … Continue reading

BVI Interface

BVI stands for Bridge-Group Virtual Interface. A BVI (Bridge Group Virtual Interface) is a routed interface that represents a set of interfaces that gets bridged. So lets say for example that in your router you have two interfaces that needs to get bridged (one wireless and one wired for example) and you want them to … Continue reading

How to encrypt Pre-Shared Keys in Your Cisco VPN

I guess you have already noticed that the VPN pre-shared keys stay in plain text even after applying password encryption. Below you can find a short explanation on how to encrypt it and keep it all safe: This is the VPN config before encryption: ****************************************************************** crypto isakmp policy 1 encr 3des authentication pre-share group 2 … Continue reading

Stateful firewall (SPI)

In computing, a stateful firewall (any firewall that performs stateful packet inspection (SPI) or stateful inspection) is a firewall that keeps track of the state of network connections (such as TCP streams, UDP communication) traveling across it. The firewall is programmed to distinguish legitimate packets for different types of connections. Only packets matching a known active connection will be allowed by the firewall; others will be rejected. … Continue reading

Virtual Routing and Forwarding (VRF)

Virtual routing and forwarding (VRF) is a technology included in IP (Internet Protocol) network routers that allows multiple instances of a routing table to exist in a router and work simultaneously. This increases functionality by allowing network paths to be segmented without using multiple devices. Because traffic is automatically segregated, VRF also increases network security and can eliminate … Continue reading

What’s IP SLA

IP SLA is a technology from Cisco® that allows Cisco devices to automatically gather data about network traffic. IP SLA data can include time-stamp information about packet flow. IP SLA data can be accessed remotely by network administrators and allows them to proactively resolve potential network data flow issues. More information in CISCO itself can … Continue reading

ip subnet-zero

What is IP Subnet Zero? Before we talk about the command, let’s ask ourselves, “In the first place, what is a zero subnet?” Under old IP subnetting rules, the all 0’s subnet was reserved for the network, and the all 1’s subnet was reserved for the broadcast. Over time, engineers found that the all 0’s … Continue reading

MVPN Frequently Asked Questions

Q. Is the Cisco Multicast Virtual Private Networks (MVPN) solution dependant on Multiprotocol Label Switching (MPLS)? A. No, Cisco’s MVPN solution operates independently from MPLS. The Service provider (SP) does not need to use MPLS for MVPNs. Q. Is MVPN a recognized standard? A. MVPNs were outlined in draft-rosen-vpn-mcast-04.txt. Cisco’s implementation is based upon the Multicast domain solution. Q. Can a … Continue reading


A “meet me room” (MMR) is a place within a colocation centre (or carrier hotel) where telecommunications companies can physically connect to one another and exchange data without incurring local loop fees. Services provided across connections in an MMR may be voice circuits, data circuits, or Internet protocol. To interconnect, companies order a patch from their cage or suite to the MMR, and then arrange for the organization … Continue reading

A Technical Comparison of IPSec and SSL

IPSec (IP Security) and SSL (Secure Socket Layer ) have been the most robust and most potential tools available for securing communications over the Inter net Both IPSec and SSL have advantages and short comings By AbdelNasir Alshamsi and Takamichi Saito from Tokyo University of Technology : pdf here :

Point of presence (POP)

A point of presence (PoP) is an artificial demarcation point or interface point between communications entities. It may include a meet-me-room. An Internet point of presence is an access point to the Internet. It is a physical location that houses servers, routers, ATM switches and digital/analog call aggregators. It may be either part of the facilities of a telecommunications provider that the Internet service provider (ISP) rents or a location separate from … Continue reading