Asad Ijaz
Lead Networking Architect and Editor at NetworkUstad. CCNP and CCNA certified, with 10+ years of experience in enterprise network design, implementation, and troubleshooting. Writes practical tutorials on routing, IPv4 management, network automation, and security fundamentals.
Network Address Translation (NAT) & RFC 1918 Private IPv4 Addresses – Exclusive Introduction
All public IPv4 addresses must be registered with a Regional Internet Registry (RIR). The registered holder of a public Internet address can assign these addresses to a network device. There is a maximum of 4.3 billion IPv4 addresses available. Still, with the increase of personal computing and the beginning of the World Wide Web, it...
Master Stateless DHCPv6 Server Configuration – A Complete Cisco Guide
Before a stateless DHCPv6 server is configured on the Cisco router, it is important to enable IPv6 unicast routing. The unicast routing is not necessary for stateless DHCPv6 servers, but it is required for RA messages due to the use of ICMPv6. In global configuration mode, we can enable the IPv6 unicast routing using the...
DHCPv6 Operation: Avoid Costly IPv6 Configuration Mistakes
Both of the stateless and stateful DHCPv6 operations are started with an ICMPv6 RA message from the router. The RA message may have been periodic or solicited by the device using an RS message. The devices start client and server communication when stateless or stateful DHCPv6 is indicated in the RA message. The DHCPv6 operation...
Configure Router as DHCPv4 Client: Instantly Get Dynamic IP (Updated 2025)
In some cases, we need a router to be configured as DHCPv4 clients just like a client computer. But this method is not recommended for routers in an internal network. The dynamic addressing is extremely useful for routers that connect to the Internet through an ISP. We can simply connect a router using just the...
Master DHCPv4 Server Configuration (Updated 2025)
A Cisco router can be configured as a DHCPv4 server. The DHCPv4 server assigns and manages IPv4 addresses from specified address pools within the router to DHCPv4 clients. The steps for configuring the DHCPv4 server on Cisco routers are the following: Excluding IPv4 Addresses The router configured as the DHCPv4 server assigns all IPv4 addresses...
Understanding DHCPv4 Message Format
Dynamic Host Configuration Protocol version 4 (DHCPv4) is a cornerstone of IP address management in IPv4 networks, automating the assignment of IP addresses, subnet masks, default gateways, and other network parameters. Based on the Bootstrap Protocol (BOOTP), DHCPv4 uses UDP ports 67 (server) and 68 (client) to exchange messages between clients and servers. This article...
Understanding DHCPv4: A Comprehensive Guide
In modern networking, every device requires a unique IP address to communicate effectively. Understanding IP address management is crucial for network management. Static IP addresses are manually assigned to devices like routers, servers, and printers with fixed locations, enabling easy remote management. However, managing IP addresses for mobile or frequently changing devices is challenging, which...
Understanding IPv6 ACLs Configuration: Step-by-Step Guide
Access Control Lists (ACLs) are a fundamental component of network security, and understanding IPv6 ACLs is essential for CCNA and CCNP certification candidates. As networks transition from IPv4 to IPv6 to accommodate the growing number of devices, mastering IPv6 ACL configuration is critical for securing modern networks. This comprehensive guide explains IPv6 ACLs, compares them...
Inbound and Outbound ACL Logic
Access Control Lists (ACLs) are a fundamental component of Cisco networking, used to filter traffic based on predefined rules. For CCNA and CCNP students, mastering ACLs is critical for securing networks and passing certification exams. ACLs allow network engineers to permit or deny packets based on criteria like source and destination IP addresses, protocols, and...
How to Configure Standard ACLs to Secure VTY Ports
All Cisco routers and switches do not allow remote access by default via terminal programs like PuTTY or Tera Term. Remote connectivity options include Telnet (VTY Port) or SSH. SSH provides encrypted sessions and is strongly recommended by Cisco for remote administration due to Telnet’s vulnerabilities. Prerequisites for CCNA/CCNP Students However, if your router’s Cisco...