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NIL IP CORNER - your valuable source of in-depth technical information

You probably noticed that the IT (being high on the list of nice-to–be-in industries) attracts more and more youngsters who believe career development is all about reading white papers. This attitude inevitably leads them to achieve only "talking–head" level of technical expertise. Ironically, they're usually the ones who provide tons of new white papers in the years to come...

Our industry needs more meat on the bones – useful advice from senior experts who started their careers in 80' or 90' and managed to keep the pace with technology (r)evolution until today. The ones who learned the hard way what an IT manager and his team is facing on a daily basis. Those who know that the technical excellence itself is useless if it doesn't contribute to the company bottom-line and make your life easier.

Ivan Pepelnjak, one of the early birds in the CCIE community (CCIE #1354) and NIL's Chief Technology Advisor, will be sharing his views, thoughts and useful technical advice in his articles once a month. Be sure to check back often!

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    ARCHIVE: IP Corner articles
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Near Field Communication

Near Field Communication (NFC) is a new technology developed for pairing two devices over a very short distance. Introduced in 2002 by the joint effort of NXP Semiconductors (a Philips Semiconductors spin-off) and Sony, it has brought to the scene new benefits for modern consumers, particularly mobile users.
In december's article, David Eror, CCNP and CCSI at NIL Data Communications, took a deep look into this interesting technology.
15.12.2011

Indoor Location-Based Services

The development of location-based services (LBS) initially focused on outdoor use. But more and more people spend their time indoors (for example shopping centers), and services for indoor users became really interesting.
David Eror, CCNP and CCSI at NIL Data Communications, explored this particular area in november's article.
21.11.2011


Location-Based Services

Although Service Providers initially offered only network access facilities (fixed/mobile - data, voice, etc.), they have added new, attractive services to their commercial offer, including services utilizing location-based awareness. Since the convergence of various mobile data technologies with the fixed network edge geographically extended Internet access availability to users, it has been increasingly interesting to offer users particular services related to their geolocation.
More details on such benefits, David Eror, CCNP and CCSI at NIL Data Communications, has gathered in this month's article.
27.10.2011


DPI Design for High Availability in Small Sites

As Deep Packet Inspection (DPI) has become more entrenched in multiple areas of the network, it has also become a strategic investment for almost all Tier-1 and Tier-2 service providers (SPs).
In this article Bojan Radulović, CCNP, CCDP, CCDA and CCSI at NIL Data Communications, focuses primarily on the application of DPI in the mobile space, as the need to enforce policies there has the greatest impact, but the various design aspects discussed here may be applied in other environments as well.
04.05.2011


Voice Implementations in 4G Networks

Choosing the voice technology within 4G radio access is a decision of which path to take, and it is generally not the same path for every operator.
Although there is no unique recipe for the short-term path, it is possible to design a solution based on an IP Multimedia Subsystem (IMS) as a long-term target architecture for the delivery of voice services and that's what David Eror, CCNP and CCSI at NIL Data Communications is talking about in March IP corner article.
22.03.2011


Voice over LTE

With the first commercial launches of 4G mobile networks in the year 2010, based on LTE, it is important to note the change of the implementation concept for the delivery of mobile voice and SMS services.
In January IP corner article, David Eror, CCNP and CCSI at NIL Data Communications, explains more about all-IP network-based architecture, which is - with the central role of the IP Multimedia Subsystem (IMS) - taking place in 4G.
21.01.2011


Mobile Service Delivery Platform

The recent experience of explosive growth of wireless data-access in 3G networks and the expected data-access "storm" in 4G networks has led to demands for change in mobile network architecture. The Evolved Packet Core (EPC), based on a single all-IP core network, is designed to meet the high demands for increased penetration of different services and smart tablet devices.
In November IP corner article, David Eror, CCNP and CCSI at NIL Data Communications reveals more about this particular area.
26.11.2010


Mobile IP Networking Overview

The development of mobile technology began with the intention to relieve the dependency of the user on a particular location. With the evolution of mobile networks, mobile data access was offered, and relatively quickly it has begun to represent an important revenue generator for the typical mobile service provider (SP).
Mobile networks have become very complex. In October IP corner article, David Eror, CCNP and CCSI at NIL Data Communications presents a brief overview of each of these technology solutions.
20.10.2010


Service-Oriented Telephony Architectures

The main goals of implementing Voice over Internet Protocol (VoIP) systems in most companies are mostly short-term, related to cutting costs and better utilizing their existing network infrastructure.
In August IP Corner article, Marko Tišler, CCVP and CCDA at NIL Data Communications, discusses architectural designs of different solutions, as well as the interfaces and standards behind the solutions.
31.08.2010


Video Quality in Service Provider IPTV Deployments – Cisco Visual Quality Experience (VQE)

The June IP corner article discusses many of the issues with service provider Internet Protocol television (IPTV) deployments and how Cisco combats these issues with a state-of-the-art solution: Visual Quality Experience (VQE).
In this article, Mihail Guguvčevski, CCSI at NIL Data Communications, describes the problems that IPTV wireline service providers face, and the Cisco way of solving them quickly, successfully and with minimal overhead. You’ll also find out more about the Cisco VQE solution, its core features and benefits and the inner workings of its architecture.
20.07.2010


In the Core of the Cloud

Do you want to understand what cloud computing is all about? Do you want to benefit from cloud computing? As a service provider and/or operator, you can provide optimized and innovative cloud computing services only with a thorough understanding of the core infrastructure of the Cloud – the virtualized data center.
In this article, Tomaž Klančnik, Customer Support Engineer at NIL Data Communications, explains the architectural components of the data center and their roles in various cloud service categories.
07.06.2010


Virtual Server Mobility Issues in the Data Center Environment

Server virtualization is something that everyone seems to be using in the data center (DC) these days. Server virtualization helps us to achieve some of these goals by allowing us to share hardware resources of a single physical server (host) among multiple virtualized servers (guests).
But the IT environment was not historically designed with such abstractions in mind. Multiple areas of guest mobility may cause issues, but for this article Vladimir Stajić, CCSI at NIL Data Communications, focuses on problems related to the Storage Area Network (SAN).
12.03.2010


Cisco TelePresence Collaboration

This article describes Cisco TelePresence collaboration, focusing on intercompany communication and interoperability. Cisco Telepresence's intercompany capabilities allow you to communicate over the Internet with other companies that already have their own TelePresence.
Uroš Strnišnik, CCVP/CCSI at NIL Data Communications, describes how Cisco TelePresence's interoperability features deliver any-to-any capabilities so that organizations with standards-based videoconferencing technologies can participate in Cisco TelePresence meetings.
10.02.2010


First-Mile Wireless: Which (G)eneration?

The jungle of acronyms – from 2G (GSM, GPRS, EDGE) through 3G (UMTS) toward 4G (LTE), interleaved with Wi-Fi, WiMAX and similar terms – makes both potential users and specifically service providers offering first-mile wireless service rather uncomfortable. In January IPcorner article, Robert Lesar, CCIE/CCSI at NIL Data Communications, provides an overview of first-mile wireless technologies, their benefits and drawbacks, focusing on future trends in access, driven by the Video over Mobile Wireless environment.
06.01.2010


Data Center Interconnections: Technical Implementations

As more and more companies deploy secondary data centers, service providers must provide suitable interconnects that offer sufficient performance. The July article explores data center interconnects on the high-level and this time we focus on what technology to use to actually implement the interconnection. In this article, Jaroslav Rajić, CCNP/CCIP and CCSI at NIL Data Communications, analyses the advantages and limitations of two distinct approaches of designing the Data Center interconnect. One approach primarily relies on OSI Layer 2 (e.g. MetroEthernet with VLANs) and the other on OSI Layer-3 approach (IP and MPLS), with several »flavours« in-between. The analysis includes the comparison of OSI Layer 2 (802.1q, QinQ, P2P EoMPLS, VPLS) and OSI Layer 3 (L3 MPLS VPN), and mentions the OSI Layer 1 options (Dark Fiber, etc.).
03.12.2009


Security of Applications Moving to a Network

As more applications have been moving to an IP network the security becomes a concern. Especially with the introduction of managed and hosted unified communications services with voice and video IP traffic on service provider network, the secure transport faces new challenges of the open and untrusted network.
In this article, Tilen Mlakar, CCNP/CCSI and Instructor at NIL Data Communications, focuses primarily on security measures of the unified communications traffic, network components and end points where the applications or their parts reside.
04.11.2009


Cisco Telepresence: A Practical Deployment Guide

The August IP corner article discusses the Cisco TelePresence, which is a high-definition conferencing environment, designed for virtualizing meetings from units set up anywhere in the world, and requiring only a standard TCP/IP-enabled network infrastructure. Cisco TelePresence allows new forms of collaboration and human interconnection, in which employees can connect easily and instantly with coworkers, customers, partners and so on anywhere in the world without leaving the office.
In this article, Mihail Guguvčevski, CCSI at NIL Data Communications, describes a typical Cisco TelePresence deployment and its related services from a practical standpoint.
10.8.2009


Data Center Interconnect

This IP corner article discusses the modern data center (DC) and its requirements for high availability. High availability can be achieved on several levels. Data centers are designed to be highly available internally. When even greater availability is required, additional high availability is achieved by using a geographically separate secondary data center. Adding a secondary data center introduces the need for interconnection between the primary and secondary data centers.
In this article, Jaroslav Rajić, CCNP and CCSI at NIL Data Communications, explores available options for that interconnection, including server clusters and Storage Area Network traffic exchange, focusing on Multi-Protocol Label Switching (MPLS) as the underlying transport technology.
6.7.2009


Evolving Toward the "Green" Data Center

In this IP corner article, Jaroslav Rajić, CCNP and CCSI at NIL Data Communications, identifies and describes the measures and actions necessary to evolve the Data Center to a more energy-efficient architecture over time.

The aim of energy-efficient Data Center architecture is to reduce the center’s carbon footprint by decreasing its power and cooling expenses (for many organizations, the main motivation behind taking these measures).
To increase overall equipment-resource utilization, a Data Center infrastructure design should employ virtualization principles. Implementing “green” Data Center architecture is easier to achieve with greenfield Data Center deployment than by upgrading an existing system.The article lists a few measures required to transform the existing Data Center to a more energy-efficient architecture and decrease its operational expenses.
4.6.2009


Designing Site-to-Site IPsec VPNs - Part 5

Do you need an on-demand fully-meshed (any-to-any) topology using IPsec in your network? And you want simplicity in configuration? Among various implementations of the IPsec the Cisco`s Group Encrypted Transport VPN (GET VPN) is the solution in this case.

Boštjan Šuštar, an internetworking expert at NIL Data Communications, in his fifth article about IPsec implementations in Cisco IOS, explains GET VPNs and their predecessor, the Tunnel Endpoint Discovery (TED). Boštjan first provides an overview of the requirements, advantages and disadvantages of TED and then focuses on GET VPNs. He describes the control plane (full-mesh topology for user data) and the data plane (hub-and-spoke topology for IKE control sessions) of the solution. Special attention is given to high availability, performance and scalability as the key server can easily become the central point of failure. Design recommendations and configuration examples are provided as well.
1.4.2009


Add a VPN to an Enterprise Network with Multi-VRF Functionality

Are you in charge of connectivity for numerous small sites spread throughout a geographic area? And you need to provide a transport for the traffic generated by the video surveillance on the remote sites? The security policy dictates that IP traffic from the video cameras is separated from the other traffic on the path to the video gateway in the data center. So, definitely, a VPN for this traffic is needed. MPLS VPN comes to mind. But Cisco offers a simpler way – a simple VPN can be implemented with Multi-VRF functionality available in all Cisco routers.
In this IP Corner article, Ivan Pepelnjak, the Chief Technology Officer (CTO) at NIL Data Communications explains the implications of building VPNs with Multi-VRF feature. The article also provides guidelines that will help you decide when to use Multi-VRF and when to deploy full-blown MPLS VPN network.
2.3.2009


Designing Site-to-Site IPsec VPNs - Part 4

The legacy technologies such as leased lines or switched networks (Frame relay, ATM) have long been replaced by public Internet or MPLS. To secure the traffic between the Local Area Networks at remote sites an IPsec is an integral part of today`s solutions.
Bostjan Sustar, in his fourth article about IPsec implementation in Cisco IOS, explains the Dynamic Multipoint VPNs (DMVPN). To some degree, DMVPNs mimic the older technologies, providing for the use of proven design choices (e.g., routing), but there are important differences to consider. Although the DMVPN is a combination of three technologies (IPsec, multipoint GRE tunnels and Next-Hop Resolution Protocol [NHRP]), it is implemented in a way that includes more intelligent interaction between these technologies, providing better resilience, performance and stability. Bostjan addresses the simple implementation as well as all enhanced options of DMVPN in his article.
4.2.2009


Flexible Extranet Implementation

Do you need to deploy an extranet? In a simple yet flexible enough way? Getting rid of limitations brought by fixed addressing? MPLS VPN implementation of an extranet brings the flexibility that will make even complex extranets deployment easier.
In this IP Corner article, Ivan Pepelnjak, the Chief Technology Officer (CTO) at NIL Data Communications, builds a case study showing how MPLS VPN implementation can solve the inflexibility in enterprise extranets deployment. Through a non-redundant extranet implementation Ivan shows the flexibility of such extranets and the ease of their integration with the existing networks or external partners.
5.1.2009


Designing Site-to-Site IPsec VPNs - Part 3

Site-to-site VPNs using IPsec can be implemented with the crypto maps or, when routed interface is needed, by GRE-tunnels. Virtual Tunnel Interfaces (VTIs) are a relatively late addition to Cisco IOS and eliminates the need for additional GRE overhead, while still providing the logical interface. Bostjan Sustar, in his third article about IPsec implementation in Cisco IOS, explains two implementation options of VTI – static and dynamic VTIs. While the first option is similar to point-to-point GREs, the dynamic option is an example of a typical remote-access implementation tool. In large site-to-site deployments the dynamic VTIs simplify management and ensure that the tunnels are always up, thus making this a site-to-site and not really a remote-access VPN.
1.12.2008


Improve the Convergence of Mission-Critical Networks with Bidirectional Forwarding Detection (BFD)

In today`s Voice over IP (VoIP) environment the final measure of network performance is provided by its users. A convergence of the network after the node failure in a traditional routing environment is simply too slow for voice users. Several attempts, mainly proprietary, have been introduced so far to speed up the network convergence. The new Bidirectional Forwarding Detection (BFD) protocol is standard based and as such interoperable between major router vendors. In this IP Corner article, Ivan Pepelnjak, the Chief Technology Officer (CTO) at NIL Data Communications, describes how BFD is used in detecting two-way communication with the next-hop router to provide sub-second network convergence.
1.11.2008


Designing Site-to-Site IPsec VPNs - Part 2

Crypto maps - used as one of the oldest Cisco IOS implementation options for IPsec – have a downside - they do not provide for a routable logical interface. When migrating from a traditional WAN or upgrading an existing WAN to use cryptography, it may be beneficial to reuse the existing knowledge of the routing protocols to implement dynamic routing and provide for high availability. With crypto maps, unfortunately, several additional mechanisms are needed to introduce the dynamic nature. In this IP Corner article, Boštjan Šuštar, the Internetworking Expert at NIL Data Communications, describes another solution - to run the point-to-point Generic Routing Encapsulation (GRE) tunnel over IPsec. This solution does not only add the ability to run a routing protocol between remote sites, but also supports IP multicast and non-IP protocols.
This is the second in a series of articles describing various methods of implementing IPsec in Cisco IOS.
1.10.2008


Secure Time Management

The April IP Corner article It’s good to be on time describes how you can use Network Time Protocol (NTP) to synchronize the real-time clock of your network devices with external time references. As soon as you start relying on your routers having pretty exact time, NTP becomes part of your mission-critical network infrastructure and has to be protected protected against intruders or impostors. Default NTP settings on Cisco IOS allow intruders to change the router’s time or even current year as soon as the router is not synchronized directly with a primary (stratum 1) NTP server. In this IP Corner article, Ivan Pepelnjak describes you how to execute a successful NTP attack on an unprotected network and the safeguards you can put in place to prevent similar attacks.
1.9.2008


Designing Site-to-Site IPsec VPNs

When designing a network solution, we often are faced with a myriad of parameters that influence the design process and the selection of the final solution. A network designer ideally would want to control as many parameters as possible apart from the business requirements, which is the basic set of requirements that guide us to the right solution. In this IP Corner article, Boštjan Šuštar describes how to design a network solution for an IPsec-based site-to-site virtual private network (VPN) by using crypto maps. This is the first in a series of articles describing various methods of implementing IPsec in Cisco IOS.
1.8.2008



The OSPF Default Mysteries

Default routing should be a simple concept, but becomes surprisingly complex in routing protocols that have multiple layers of default routes. In this IP Corner article, Ivan Pepelnjak describes how the Open Shortest Path First (OSPF) protocol uses default routes and how various OSPF-generated default routes interact in typical network scenarios.
1.7.2008


Servers in Small Site Multi-Homing

If you want to deploy high-availability public servers within your network, you should implement proper multi-homing solution including BGP routing with the Service Providers. But even if you use alternative solutions, like the ones presented in the previous IP corner article Small Site Multi-Homing, there are ways to deploy public servers within your site. In this IP Corner article, Ivan Pepelnjak describes the challenges you’ll face and give you several design and deployment guidelines.
1.6.2008



Scalable Policy Routing

Network designers and implementers try to avoid policy routing, as its common implementation in Cisco IOS requires a complex mix of access-lists and route-maps that have to be deployed on a hop-by-hop basis. In most cases, distance vector routing protocols can be used to implement policy routing requirements in large networks. In this IP Corner article, Ivan Pepelnjak describes how you can use BGP to implement an architecture where a set of applications should prefer a different subset of links than other applications.
1.5.2008



It's Good to be on Time

The importance of having accurate time on distributed servers and even personal workstations has been recognized long time ago by the IT managers, but it hasn’t been applied consistently to the networking devices. In this IP Corner article, Ivan Pepelnjak, describes the importance of time synchronization for networking devices, the basics of Network Time Protocol (NTP) that is commonly used to synchronize IP hosts and routers, how to use it on Cisco routers and IOS-based switches and how to implement it in a highly scalable way.
1.4.2008



Designing Fast Converging BGP Networks

Border Gateway Protocol (BGP) was always considered a mastodonic routing protocol: huge, complex, hard to understand and configure, and very slow to converge. When Cisco decided to use it to implement layer-3 Virtual Private Networks (VPNs) due to its enormous route carrying capabilities, the slow convergence of BGP became a liability. The Cisco engineers decided to fix the BGP code, resulting in a routing protocol with decent convergence times. In this IP Corner article, Ivan Pepelnjak illustrates how you can optimize BGP convergence in your network without overloading the routers running it.
1.3.2008



When OSPF Becomes a Distance Vector Protocol

Contrary to common wisdom, OSPF is not a pure link-state protocol. It uses link state algorithms within an area, but behaves almost like a distance vector protocol between the areas. This distinction introduces temporary routing instabilities into multi-area OSPF network that does not use inter-area summarization. In today's IP Corner article, Ivan Pepelnjak illustrates how this unexpected behavior can affect the convergence of your network and how you can use proprietary extensions of Cisco IOS to alleviate the undesired side effects of OSPF.
1.2.2008



The Never-Ending Story of IP Fragmentation

After years of struggles, the IP fragmentation remains one of the challenges in IP network deployment, particularly if you have to implement extra layers in the protocol stack (like PPP over Ethernet) or if you use any IP-over-IP encapsulation or IP encryption techniques. In this IP Corner article, Ivan Pepelnjak describes the reasons behind IP fragmentation, how the Path MTU Discovery works and how the various mechanisms can be used on Cisco routers to alleviate the IP fragmentation-related problems.
1.1.2008



Bring your Network Closer to Five Nines with Graceful Shutdown

The five nines (99.999% availability of a service) is the holy grail of many Chief Information Officers (CIO). To reach this goal, the average monthly downtime should be less than 25 seconds, which is extremely hard to achieve even in a fully redundant architecture. The scheduled router outages (upgrades, hardware maintenance), while being necessary, can also impact the safety margin you have. In this IP Corner article, Ivan Pepelnjak describes how you can reduce the network downtime caused by scheduled router outages if your network uses OSPF (Open Shortest Path First) routing protocol.
1.12.2007

Load Balancing in BGP Networks

A few years ago, the traditional wisdom was that you could not do load balancing in networks using Border Gateway Protocol (BGP) as their core routing protocol. The technology, actually its implementation in Cisco IOS, has evolved since then, resulting in a number of load balancing options for BGP-based networks. However, even though it is possible to load-balance in BGP networks, it is still not as easy as Interior Gateway Protocol (IGP; for example OSPF or EIGRP)-based load balancing, which happens automatically. In this IP Corner article, Ivan Pepelnjak describes load-balancing options available with BGP.
1.11.2007

Changing the Routing Protocol in Your Network

Selecting the right IP routing protocol is one of the most important decisions in the network design phase. But even after careful consideration of all facts known to you at that time, you might get it wrong and have to change the routing protocol after the network has already been in production for some time. In this IP Corner article, Ivan Pepelnjak will give you some suggestions on how to migrate from one routing protocol to another in a moderately complex network.
1.10.2007

Increase the Stability of your Network

The introduction of real-time mission-critical applications (like voice-over-IP) into data networks has prompted many network designers to tune their routing protocols for faster convergence. The resulting network usually becomes highly susceptible to repetitive failures (e.g. a flapping interface), which can cause recurring instabilities in large parts of the network and significant data loss. In this IP Corner article, Ivan Pepelnjak describes how the IP Event Dampening, introduced in Cisco IOS release 12.3, can be used to increase the stability of your network, as well as how you can cope with scenarios that are beyond the scope of this feature.
1.9.2007

Redundant Small Site Multi-Homing

The February IP Corner article Small Site Multi-Homing described how to implement the small site multi-homing with existing Cisco technologies in the existing ISP environment. That article has generated lots of responses, most of them being questions about redundant implementation of the same principles. Therefore Ivan Pepelnjak decided to describe how to extend the small site multi-homing design with a set of redundant routers. The final design still retains the administrative simplicity of the original solution – with no need to own public IP address space, autonomous system number or to run Border Gateway Protocol (BGP).
1.7.2007

Cisco Router: the Swiss Army Knife of Network Services

The cost optimization in the IT industry is affecting all segments of network design and implementation. For example, some IP services like DHCP and DNS, which were previously distributed throughout the network, are now concentrated on central servers. As these services are vital for the proper operation of IP networks, your remote sites might lose even intra-site connectivity if their link to the core site fails. Fortunately Cisco routers can provide most network services locally, including DNS and DHCP. In this IP Corner article, Ivan Pepelnjak describes how you can use a Cisco router as a local DNS server.
1.6.2007

Enhance the IOS User Interface

Have you ever wanted to fine-tune the IOS show commands to provide you with the exact information you need instead of having to dig through long screens full of data you are not interested in to find what you need? In this IP Corner article, Ivan Pepelnjak describes how to use the simple filters provided by Cisco IOS to pick only the information you need from the printouts, as well as how to generate tailored printouts (even combining outputs from multiple show commands) with Tcl shell introduced in IOS release 12.3(2)T.
1.5.2007

Scaling EIGRP Networks with Stub Routers

Enhanced Interior Gateway Routing Protocol (EIGRP), Cisco’s proprietary yet hugely successful and widely deployed routing protocol is known to behave disappointingly in inadequately designed networks. Cisco has improved EIGRP’s behavior dramatically with the introduction of stub routers in Cisco IOS release 12.0(7)T. However, this feature has remained a well-hidden mystery. In this IP Corner article, Ivan Pepelnjak explores the typical problems that the EIGRP stub routers help to solve, describes how the introduction of stub routers improves network stability and implements a fully redundant remote location (stub site); yet another very common design requirement that is not documented anywhere.
1.4.2007



Replacing Configuration on a Working Router

Have you ever faced a situation where you have badly misconfigured your router and had to roll back the configuration to a previous known state? Assuming that the working configuration was still saved in the NVRAM, you only had two options - to manually work out the configuration commands to bring the router back to the previous state or to reload the router. In both cases the time was running too fast - both for the users who were facing the network downtime and especially for you. In this month`s IP Corner Ivan Pepelnjak describes how to use the Cisco IOS Configuration Replacement and Configuration Rollback feature to replace the current running configuration with any saved Cisco IOS configuration file.
1.3.2007

Small Site Multi-Homing

High-availability seems a de-facto requirement of enterprise networks, even more so today as the network managers have to migrate from traditional highly robust technologies to MPLS/VPN- or Internet-based transport networks. Usually these migrations result in multi-homed central sites, while the small remote sites end up having a single best-effort upstream connection. In this month's IP Corner article Ivan Pepelnjak describes how to implement the small site multi-homing with existing Cisco technologies in the existing ISP environment.
1.2.2007



Keep Track of Router Configurations with Configuration Archive

Can you answer these questions when faced with a network-down situation:

  • Do we have a backup of a working configuration?
  • What was the router configuration before the last mistake was committed to the startup configuration?
  • Do we have a copy of the configuration that was used a week (or a month) ago?

If not, maybe it's time you deploy Configuration Archive feature described in this article.
1.1.2007

Router Configuration Management ... Too Good to be True?

In Cisco IOS release 12.4, Cisco finally gave us fundamental router configuration management tools that we've been sorely missing in the last 20 years. In this month's IP corner Ivan Pepelnjak describes how he tested them and uncovered a few unpleasant surprises along the way.
1.12.2006

Perfect load-balancing: How close can you get?

Multi-protocol Label Switching (MPLS) is usually regarded as a Service Provider technology, but in this month's article, Ivan Pepelnjak shows you how you can deploy MPLS Traffic Engineering (MPLS-TE) in your enterprise network to achieve optimal load-balancing in a highly redundant setup.
1.11.2006

Using a Web Server to Manage Your Router Configurations

Starting with IOS release 12.3(2)T, you can download and upload software and configuration of your Cisco router to a web server, greatly simplifying router management and enabling the network managers to use the same infrastructure as the rest of their IT department. In this article, you’ll find the description of the required configuration steps for both the Cisco routers and the web server on which you want to store the router configurations.
1.10.2006