The Scenario is this…Company A has purchased Company B. One is an enterprise of thousands of users, the other a mid size company in the multiple hundres. However, as would happen to be the case, both companies utilize an overlapping subnet. To further complicate the issue it has been decided that both companies need to terminate at Company A’s core and utilize a single unified instance of EIGRP. As part of this scenario, both companies need to be abble to access each others networks but luckily it has been determined that neither need to be able to access each others overlapped networks. Additionally both companies advertise different bit masks on their overlapping networks. This is something that we can work with.
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The scenario looks like this. You’ve got a branch office with a single router connecting to your corporate office over the WAN. In your branch office you have a single layer 2 switch and a desire to separate traffic into multiple broadcast domains. Maybe you want an easy way to allow only HR computers to connect to a very specific branch office server and the only place for any restriction of traffic is on that branch office router. Here is where your router on a stick comes into play.
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Cisco routers are capable of doing many more things than simply routing packets. In fact, it can operate as a small DHCP server when needed. By no means is it a replacement for your enterprise, centrally managed DHCP server but it does have its applicable scenarios. Lets say you have a branch office that has its own server for any particular reason. Maybe it is a local file share for an engineering departments CAD program and rather than having all file traffic from opens and saves traverse the WAN during the day, you simply run backs of that server across the WAN at night. Continue reading
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Routing is at the core of the network infrastructure. Routing is what ultimately lets you get from point A to point B not only in your own network, but also across the entirety of the world wide web. Routing in its simplest form tells your network devices the path to get to another network device located on another network. This was originally handled by creating static routes to the required destinations.
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Todays enterprise network is heavily focused on providing as near to 100% uptime as possible. Newer technologies such as virtualization and server clusters have been a focal point in achieving this level of service for some time now. However, an often missed opportunity to provide that level of service exists in the core of your infrastructure. Many medium size organizations will implement a server monitoring resource to measure and track the uptime on their core applications and infrastructure servers such as DHCP, DNS, SharePoint, Active Directory, and so on. Often times this monitoring server is located within the data center, and likely on the same subnets as the servers themselves. This can quickly skew your uptime numbers in the sense of “can my users reach the servers?”. While true, the uptime of the servers may be near 100% from the standpoint of the monitoring system, that does not indicate the ability for your users to reach the servers, or in the same concept, your servers to reach your users. Enter default gateway redundancy.
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In my chase for CCNP I came across virtual links while studying for the CCNP ROUTE exam. When I first read through the concept I was slightly lost during the description. However, upon a couple of runs through a lab it became clear on how easy the were. Before I list the condensed two step (or focus points if you will) to look at let’s look at what a virtual link is and why we would use it.
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