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Wael Osama

Routers’ Operating systems

The router operating system is a piece of software responsible for managing the router resources by controlling and allocating memory, prioritizing system requests and processes, controlling I/O devices and managing file systems. The most two famous router operating systems are Cisco IOS and Juniper JUNOS. Cisco IOS is a monolithic OS which means it runs as a single operation with all processes sharing the same memory space. This means a bug in o­ne process can impact or corrupt other processes also means that adding new features to the OS requires upgrading the full IOS image itself. JUNOS is a modular …

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Native VLAN

Native VLAN is a dot1Q concept that was created for backward compatibility with old devices that don’t support VLANs. Full story detailed below.. How Native VLAN works? Frames belonging to the native VLAN are not tagged when sent out o­n the trunk links so older devices can simply understand. Frames received untagged o­n the trunk links are set to the native VLAN. Note: this default behavior can be changed by configuring the switch to tag native VLAN frames using the global command vlan dot1q tag native In the below diagram two switches are connected with a trunk link; each switch …

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PBR as a QOS tool

In order to apply QOS policies in your network, traffic should be classified first. There are many techniques available for packet classification. PBR is one of these techniques as discussed below. PBR can be used to match a specific flow and then apply QOS policies on it, like marking this traffic or routing the traffic to special optimized or dedicated connections to handle this traffic type. For example you may have two internet connections, one for normal internet traffic [FTP, HTTP, downloads] and another one for critical applications or to be dedicated only for use by the managers or critical …

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Routers’ Memory types

The memory come in many forms for several storage purposes such as to store the operating system , the configuration, the bootstrap, packets, and so forth. Below is a detailed description of all memory types used in routers and the purpose of each. BootROM BootROM is used for permanently the storage of the startup diagnostic code (ROM Monitor). The main task for the BootROM is to perform some hardware diagnostics during bootup on the router, Power On Self Test (POST), and to load the Cisco IOS software from the Flash to the Memory. Flash Flash memory is a non-volatile memory …

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