Home > CCNA, Cisco, ICND2 > Access List, NAT and VPN connections, oh my!

Access List, NAT and VPN connections, oh my!

Another set of terms and concepts that almost every IT professional tosses around but does not necessarily understand the whole story and configuration behind them. For the couple of weeks this is what I’ve been covering in the prep for the ICND2 exam, and let me tell you, they are awesome. All three of these have their own purpose but are typically combined to offer a form of basic network security on your router/end point.

Access lists at their core are used to permit or deny access from one section of a network to another section of the network but, are also used in configuring NAT.

NAT is used to allow internal private IP addresses to access external resources by translating them to public addresses. There are multiple versions of NAT, the most popular being PAT which allows the use of one external IP address to represent multiple internal private network addresses. This is done by assigning a unique source port to the end of your public IP address for example internal source IP address and port 192.168.1.20:25222 which would translate to 67.112.2.5:25222 on your endpoint router.

VPN, or Virtual Private Network, connections allow hosts or networks to connect to other networks over the internet via an encrypted connection. This allows employees of your organization to work from anywhere in the world and still securely access resources at the main office as well as connecting branch offices back to the main office without the need of expensive dedicated connections.

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