Network PC World

When it comes to securing communication over the internet, Virtual Private Networks (VPNs) are a cornerstone of modern networking. Two popular types of VPNs are SSL VPN and IPSec VPN . While both serve to encrypt and secure data, they differ significantly in terms of technology, use cases, and implementation. This blog post will help you understand these differences and choose the right solution for your needs. What is SSL VPN? An SSL VPN uses the Secure Sockets Layer (SSL) or its successor, Transport Layer Security (TLS) , to create a secure connection. It operates at the Application Layer (Layer 7) of the OSI model and is designed to provide secure access to specific resources over the internet. Key Features of SSL VPN: Ease of Use: Accessible via a standard web browser without the need for dedicated client software. Granular Access Control: Allows users to access specific applications or resources rather than the entire network. Port Usage: Uses TCP port 443, which is rarely...

The Complete Public Key Infrastructure (PKI) Process: From Key Generation to Certificate Verification Public Key Infrastructure (PKI) is the backbone of secure communication on the internet. It ensures that sensitive data exchanged between clients and servers remains private and authentic. This blog post will guide you through the entire PKI process, from generating keys to verifying certificates and ensuring they haven't been revoked. 1. Key Pair Generation The first step in PKI is generating a public-private key pair using an asymmetric cryptographic algorithm, such as RSA or ECDSA: The private key is securely stored on the server and never shared. The public key is included in the certificate and shared with the Certificate Authority (CA) during the certificate request process. This key pair enables encryption and decryption, which are essential for secure communication. 2. Creating a Certificate Signing Request (CSR) The server creates a Certificate Signing Request (CSR) to...

In BGP (Border Gateway Protocol), managing route updates and reapplying new policies can sometimes be challenging, especially if you want to avoid resetting the BGP session. Two methods allow you to update routing policies without tearing down the session: BGP Soft Reconfiguration and BGP Route Refresh . While both methods serve the same purpose, they work differently and have distinct impacts on your router's resources. This post explains the key differences between Soft Reconfiguration and Route Refresh , when to use each, and why Route Refresh is preferred in most modern networks. 1. What is BGP Soft Reconfiguration? BGP Soft Reconfiguration is an older method of applying new policies (like route maps, filters, or prefix lists) without resetting the BGP session. It works by storing a local copy of all the routes received from a BGP neighbor before applying inbound policies. This local route copy allows the router to reprocess the routes when a policy change occurs. How So...

AS Path Prepending is a BGP feature used to make a specific path appear less preferred by artificially lengthening the AS path. This is done by adding your AS number multiple times to the AS path. It is a common method to influence inbound traffic from external networks. Longer AS Path = Less preferred route . Example Scenario : You have two ISPs: ISP1 (through CE1) and ISP2 (through CE2). You want inbound traffic from the internet to prefer ISP1 over ISP2. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP2): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE2 (AS Path Prepending to Make ISP2 Less Preferred) : Create a route map to prepend your AS path multiple times for CE2: route-map PREPEND_AS permit 10 set as-path prepend 65001 65001 65001 Apply this route map to the neighbor in the BGP configuration for CE2: router bgp 65001 neighbor 10.0.2.1 remote-as 65002 neighbor 10.0.2.1 ro...

The Multi-Exit Discriminator (MED) is used in BGP to control inbound traffic into your AS. It tells a neighboring AS which entry point into your network it should prefer when there are multiple links between your AS and the neighboring AS. The lower the MED value , the more preferred the path. MED is only honored between the same neighboring AS . Example Scenario : You are connected to ISP1 via two routers, CE1 and CE2 , and want to control which router ISP1 uses to send traffic into your AS. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP1): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE1 (Lower MED, More Preferred) : Create a route map to set the MED to 50 for CE1: route-map SET_MED permit 10 set metric 50 Apply this route map to the neighbor in the BGP configuration for CE1: router bgp 65001 neighbor 10.0.1.1 remote-as 65000 neighbor 10.0.1.1 route-map SET_MED out Configuratio...

In BGP, Local Preference is used to control the outbound traffic path. It helps you decide which egress point (exit point) should be used when you have multiple connections to external networks, such as ISPs. Local Preference is an attribute that is local to your AS and is shared with all iBGP peers but not with eBGP neighbors. Higher Local Preference = More preferred outbound path. Example Scenario : You have two external links: ISP1 (via CE1) and ISP2 (via CE2). You want traffic to prefer ISP1 for all outbound traffic. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP2): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE1 (Higher Local Preference) : Create a route map to set the local preference to 200 for routes learned from CE1: route-map SET_LOCAL_PREF permit 10 set local-preference 200 In the BGP configuration for CE1, apply this route map to the neighbor: router bgp 65001 ne...

DNS (Domain Name System) plays a critical role in how users and systems find resources on the internet or within internal networks. Whether it's managing an internal domain in an enterprise or delegating parts of a domain for traffic distribution, DNS setups vary widely depending on needs. In this blog post, we’ll break down the different types of DNS setups, including authoritative DNS servers, DNS delegation, and how internal DNS functions within organizations. 1. Authoritative DNS Server An Authoritative DNS server is the final source of truth for a specific domain. When someone queries a domain (e.g., example.com ), the authoritative DNS server for that domain holds the DNS records (A records, CNAME, MX, etc.) and responds with the corresponding IP address. Key Points: Who can host it? Authoritative DNS servers are often hosted by domain registrars (e.g., GoDaddy, Namecheap) or cloud DNS providers (e.g., AWS Route 53, Cloudflare). However, organizations can also host their ...