My Netwok Dictionary

Although you can use a router to segment the LAN, it is used primarily as a WAN device. Routers have LAN and WAN interfaces. In fact, routers communicate with each other through WAN connections. Routers are the backbone of the large internal networks and the Internet. It operates at Layer 3 of the OSI model, making decisions based on network addresses.

The two main functions of a router are the selection of the best route to and switching of frames to the corresponding interface. The router accomplishes this through the creation of routing tables and information sharing network of these tables with other routers. An administrator can maintain the routing tables by configuring static routes, but generally speaking, routing tables are maintained dynamically through the use of a routing protocol that exchanges information with other routers network topology (route). Read the rest of this entry »

The rapid growth of the Internet has left stunned most observers. One of the reasons why the Internet has grown so quickly is due to the flexibility of the original design. Without the development of new technologies for IP address assignment, the rapid growth of the Internet would have exhausted the current number of IP addresses. To compensate for this lack of IP addresses, we searched for different solutions. One solution widely deployed, is the Network Address Translation (NAT).

NAT is a mechanism for conserving registered IP addresses in large networks and simplifying management tasks IP address. Tools package is routed through a network device, usually a border router or firewall, the source IP address is translated from a private internal network address to a routable public IP address. Read the rest of this entry »

Despite the complexity of DUAL, configuring EIGRP can be relatively simple. The EIGRP configuration commands vary according to the protocol to be routed. Some examples of these protocols are IP, IPX and AppleTalk. This article describes how to configure EIGRP for IP protocol.

Follow these steps to configure EIGRP for IP routes:

1. Use the following to enable EIGRP and define the autonomous system:

router (config) # router eigrp autonomous-system-number

The autonomous system number is used to identify all routers belonging to the internetwork. This value must match all routers within the internetwork. Read the rest of this entry »

By default, routers learn routes to the destination in three different ways:

Static routes: The system administrators manually define static routes as the next hop to a destination. Static routes are useful for safety and traffic reduction as it does not know any other route.

Default routes: The system administrator manually defines default routes as the route to take when there is no known route to the destination default routes keeps routing tables shorter. When there is no entry for a destination network in a routing table, the packet is sent to the default network.

Dynamics routes: Dynamic routing means that the router will find out the routes to the destination by means of periodic updates sent from other routers. Read the rest of this entry »

Sometimes it is useful to view or alter the content of the kernel ARP tables, for example, when you suspect a duplicate IP address is the home of an intermittent problem on your network. The arp tool was made for situations like this. Your options are: arp [-v] [-t tipohw]-[machine] arp [-v] [-t tipohw]-s machine direccionhw arp [-v]-d machine [machine...]

All arguments hostname can be symbolic names or IP addresses in dotted quad notation. The first command displays the table row corresponding to the specified IP address or machine, or if none is passed, will display all records. For example, invoking arp in vlager would get: showing vlager, vstout and vale Ethernet addresses. The list can be limited to a hardware type specified using the option -t. The possible values are ether, ax25, or ProNet, and refer to 1 0Mbps Ethernet, AMPR AX.25, and IEEE 802.5 token ring equipment, respectively.

The option-s is used to permanently add the Ethernet address of the machine specified the ARP tables. The argument specifies hardware address, which by default is supposed to be an Ethernet address specified as six hexadecimal bytes separated by colons. You can even define the hardware addresses for other types of hardware, using the option -t. Read the rest of this entry »

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).

Read the rest of this entry »

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

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 »

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 »

The two main classes of IGP are distance vector and link state. Both types of routing protocols seek routes through autonomous systems. Distance vector and link state routing protocols use different methods to perform the same tasks.

Algorithms link state routing, also known as algorithms Open Shortest Path First (OSPF), maintains a complex database of topology information. The routing algorithm maintains link-state full details of distant routers and interconnection.

On the other hand, the distance vector algorithms provide information not specified on distant networks and no information about remote routers. It is important to understand how routing protocols operate link state to configure, verify and troubleshoot. This module explains routing protocols, link state, describes their functions, describes the algorithm used and highlights the advantages and disadvantages of link-state routing. Read the rest of this entry »