My Netwok Dictionary

In the case of remote access VPN or VPDN, the possibility of encapsulating PPP frames, which are the ones that transmit normally a VPN client of this type on IP datagram. There are various options to encapsulate PPP (which in turn can encapsulate other protocols of network, such as IPX, etc or possibly IP) over IP.

• The PPTP protocol (Point-to-Point Tunneling Protocol) specifies a technique for encapsulating PPP frames but does not add authentication services. These services can be performed using the same protocols using PPP, as PAP (Password Authentication Protocol) or CHAP (Challenge Handshake Authentication Protocol).

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It should be assigned a static local DLCI to network layer address of a remote router when the remote router does not support Inverse ARP protocol. This is also true when the need to control broadcast traffic and multicast through a PVC. This method of assigning DLCI in frame relay is called static mappings.

Use the command frame-relay map protocol protocol-address dlci [broadcast] to assign a static address to the remote network layer local DLCI.

Problems range of routing updates in NBMA:

By default, a frame relay network provides connectivity non-broadcast multiple accesses (NBMA) between two remote sites. NBMA environment is considered equal to other environments multiple access media, such as Ethernet, in which all routers are in the same subnet. However, to reduce costs, NBMA clouds are usually built following a star topology. In the star topology, physical topology does not provide an access function does provide multiple Ethernet. The physical topology consists of multiple PVC.

The NBMA topology of frame relay may cause two problems:

• Problems relating to scope routing updates.
• The need to replicate broadcast packets in each of the PVC when a physical interface contains more than one PVC.

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This article explains the differences and similarities between EIGRP and IGRP. Distance information and distance vector technology used in IGRP is also used in EIGRP.

EIGRP improves the convergence properties and operates with greater efficiency than IGRP. This allows a network has an improved architecture and can maintain the current investment in IGRP.

Comparisons between EIGRP and IGRP can be divided into the following categories:

• Compatibility Mode
• Calculation of metrics
• Number of hops

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Although the original objective of the ICMP protocol is the notify errors and unusual conditions (which require special attention with regard to the IP protocol), it is possible to make an improper use of this protocol for identifying traces of a remote system.

Here are some examples of how to obtain these tracks from the various answers given by the ICMP traffic:

ICMP echo:

The use of ICMP echo traffic allows the exploration of active systems. Thus, this exploration is to identify existing equipment within the network you want to explore, normally accessible from the Internet. Read the rest of this entry »

CHAP is used to initiate a link and check, periodically, the identity of the remote node through an exchange of signals three routes on a regular basis. CHAP is carried out upon establishing the initial link and is repeated during the time that the last link.

After completing the establishment phase of the PPP link, the host sends a test message to the remote node. The remote node responds with a value calculated by one-way hash function that, in general, Message Digest 5 (MD5). This response is based on the password and check messages. Read the rest of this entry »

EIGRP automatically summarizes the routes on the border with class. This is the boundary where the network address ends in accordance with the definition of class-based addressing. This means that even though RTC is connected to the subnet 2.1.1.0 only, post that is connected to the entire Class A network, 2.0.0.0.

In most cases, automatic summarization is beneficial because it maintains the routing tables as compact as possible. However, automatic summarization may not be the best option in certain cases. For example, if there are non-contiguous subnets automatic summarization must be disabled for routing to work properly.

To turn off automatic summarization, use the following command:

router (config-router) # no auto-summary Read the rest of this entry »

The ICMP protocol does not use service port number and is therefore a little more difficult to collect details. ICMP uses a number of different types of datagrams. Many of these are harmless and normal, while others will only be observed under special circumstances. Sometimes people with too much time on their hands try to maliciously damage a user’s access to the network, generating large amounts of ICMP messages.

This is commonly called saturated ping2. While the IP accounting can not do anything to prevent this problem (although the IP firewall can help!), we can at least put accounting rules in a place that will show whether someone has been trying. ICMP does not use the ports as these do it TCP and UDP. Read the rest of this entry »

The LAN design has evolved. Until recently, network designers used hubs and bridges to build networks. Switches and routers are key components of the LAN design and the capabilities and performance of these devices are getting better.

This module describes the roots of modern Ethernet LAN with emphasis on the evolution of Ethernet/802.3, the architecture of most widespread LAN implementation. A look at the historical context of the development of LANs and various network devices that can be used in the various layers of the OSI model will help students better understand the reasons why network devices have evolved. Read the rest of this entry »

This article presents the store and forward switching and cut-through switching. The following two switching modes are available for sending frames:

• Store and forward switching: The complete frame is received before performing any type of shipment. We read the source and destination addresses and filters are applied before sending the frame. Latency occurs while the frame is being received. Latency is greater with larger frames because the entire frame must be received before the start of the switching process. The switch can check all frames to see if there are errors, which can detect more errors.
• Cut-through switching: The plot is sent through the switch before it receives the complete frame. At a minimum, the destination address of the frame must be read before the plot can be sent. This mode reduces the latency of transmission, but also reduces the error detection.

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PPP configurable aspects include methods of authentication, compression, error detection, and if it supports multilink or not. The following section describes the various PPP configuration options.

Configuring PPP:

The following example enables PPP encapsulation on serial interface 0 / 0:

Router # configure terminal
Router (config) # interface serial 0 / 0
Router (config-if) # encapsulation ppp

Compression software point to point can be configured interfaces serials that use encapsulation PPP. Compression runs on the software and can affect system performance significantly. Compression is not recommended if most of the traffic consists of compressed files. Read the rest of this entry »