Browsing articles in "Tutorial"
Nov
1
2008
How to optimize HSRP
optimize_hsrp_2

As you see in the article “Implementing High Availability with HSRP“, it is quite simple configure Hot Standby Router Protocol. Some cases require a custom configuration, using priority, track, preempt etc…and these are: The standby preempt interface configuration command allows the router to become the active router when its priority is higher than all other HSRP-configured routers in this Hot Standby group. The configurations of both routers include this command so that each router can be the standby router for the other router. If you do not use the standby preempt command in the configuration for a router, that router […]

Oct
29
2008
Implementing High Availability with HSRP

The Hot Standby Router Protocol (HSRP) is a Cisco proprietary first-hop redundancy protocol (FHRP) designed to allow for transparent fail-over of the first-hop IP router, and has been described in detail in RFC 2281. HSRP provides high network availability by providing first-hop routing redundancy for IP hosts on Ethernet, Fiber Distributed Data Interface (FDDI), Bridge-Group Virtual Interface (BVI), LAN Emulation (LANE), or Token Ring networks configured with a default gateway IP address. HSRP is used in a group of routers for selecting an active router and a standby router. In a group of router interfaces, the active router is the […]

Oct
23
2008
Multiple privilege levels
Multiple-privilege-levels

Cisco IOS permits to define multiple privilege levels for different accounts. This could be useful when many people work on the same router / switch, but with different roles (operator, tecnhician, network manager) and there is no time to implement an authentication server. There are 16 different privilege levels that can be used. Level 0 is user mode. Level 15 is the privileged mode. Level 1 through 14 are available for customization and use.

Oct
10
2008
Cisco basic configuration
cisco-basic-configuration

There are some “standards” steps used for basic configuration on your Cisco router/switch: Define the hostname Assign the privileged level Secure console port Secure VTY lines Encrypt the passwords

Sep
29
2008
How to analyze traffic with SPAN feature
Cisco-Span

Usually when we admin a network, we need to know what are the protocols used more frequently, and why not, discover if someone are using improper P2P software; so we can use SPAN. The Switched Port Analyzer (SPAN) feature, which is sometimes called port mirroring or port monitoring, selects network traffic for analysis by a network analyzer. For example, if you want to capture Ethernet traffic that is sent between host A and host B, you must implement SPAN feature. In this diagram, the sniffer is attached to a port (destination SPAN port) that is configured to receive a copy of […]

Sep
28
2008
Routed versus routing protocols
Routed-versus-routing-protocols

Two categories of protocol exist at the network layer: routed and routing. A routed protocol is a Network Layer protocol that is used to move traffic between networks. Routed protocols allow a host on one network to communicate with a host on another, with routers forwarding traffic between the source and destination networks. IP, IPX, and AppleTalk are all examples of routed protocols. Routing protocols let routers route routed protocols after a path has been determined. RIP, IGRP, EIGRP, OSPF, IS-IS, BGP are all examples of routing protocols.

Sep
23
2008
The configuration register
The-configuration-register

The configuration register can be used to change router behavior in several ways, such as: how the router boots (into ROMmon, NetBoot) options while booting (ignore configuration, disable boot messages) console speed (baud rate for a terminal emulation session) To view the current setting of the configuration register, use the show version command:

Sep
17
2008
An introduction to SNMP
An-introduction-to-SNMP

In a network environment, it is a good practice monitor Cisco devices. One of the most famous protocol to control and manage Cisco devices is SNMP (Simple Network Management Protocol). SNMP exposes management data in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications. The main features are: The SNMP is an application layer protocol that facilitates the exchange of management information between network devices. It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. It uses UDP port 161 for the […]

Sep
13
2008
Using AutoSecure to secure a router
Using-AutoSecure-to-secure-a-router

Due to the number of CLI commands needed to manually disable services in an attempt to make the router more secure, Cisco introduced the AutoSecure feature from the Major Release 12.3 and subsequent 12.3 T. AutoSecure is a good command for customers without special Security Operations Applications because it allows them to quickly secure their network without thorough knowledge of all the Cisco IOS features. The command is available for the Cisco 800, 1700, 2600, 3600, 3700, 7200, and 7500 Series Routers. There are 2 mode: Interactive mode: prompts the user with options to enable and disable services and other […]

Sep
9
2008
How a DHCP server works and how to configure it on a Cisco router
how-a-dhcp-server-works-and-how-to-configure-it-on-a-cisco-router

The Cisco DHCP server feature is a full implementation that assigns and manages IP addresses from specified address pools to DHCP clients. After a DHCP client has booted, the client begins sending packets to its default router. The IP address of the default router should be on the same subnet as the client.