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
IPv4 only has about 4.3 billion addresses total — a number that looked enormous in the early 1980s and nowhere near enough once personal computing and the web took off. Network Address Translation, alongside RFC 1918 private addressing, is the pairing that kept IPv4 usable for decades past when it otherwise would have run out....
Configuring a Stateless DHCPv6 Server on a Cisco Router
Stateless DHCPv6 does one job and one job only: it hands out supplementary configuration — DNS servers, a domain name — to clients that have already generated their own IPv6 address through SLAAC entirely on their own. It never assigns an address itself, under any circumstances. That distinction shapes every command in this setup, and...
How DHCPv6 Operation Works
DHCPv6 doesn’t start the way DHCPv4 does. There’s no equivalent of a client blindly broadcasting into the dark hoping something answers — in IPv6, the very first thing that happens is an ICMPv6 Router Advertisement, and that message is what tells a client whether it should even bother starting a DHCPv6 conversation at all in...
Configuring a Router as a DHCPv4 Client
A router can learn its own IP address the same way an ordinary client computer does — by asking a DHCP server for one, instead of having an address typed in manually on the device itself. This isn’t the normal setup for a router’s internal, LAN-facing interfaces, where a stable, known address matters. But it’s...
Configuring a Basic DHCPv4 Server on a Cisco Router
A Cisco router doesn’t need a dedicated server to hand out IP addresses — IOS can run the DHCP server role itself, assigning and managing addresses from a defined pool to clients on the LAN without any separate hardware or software required. This is the “Easy IP” setup common in small offices and labs, and...
Understanding the DHCPv4 Message Format
Every DHCPv4 exchange — Discover, Offer, Request, Acknowledge — rides inside the same fixed DHCPv4 message format, inherited from BOOTP. Once you know what the message format is, what each field actually holds, and why, reading a DHCP packet capture stops being guesswork and starts being straightforward: the fields tell you exactly what stage of...
Understanding DHCPv4: A Complete Guide
Every device on a network needs a unique IP address to communicate. Static addressing — manually typing an IP into a router, server, or printer — works fine for devices that never move and never change. It falls apart fast for laptops, phones, and anything else that joins and leaves the network constantly. That’s the...
Understanding IPv6 ACLs Configuration: Step-by-Step Guide
Access Control Lists are a fundamental component of network security, and understanding IPv6 ACLs matters more every year as networks transition from IPv4 to accommodate the growing number of connected devices. IPv6 ACLs share the same core purpose as their IPv4 counterparts — filtering traffic based on permit and deny statements — but differ enough...
Inbound and Outbound ACL Logic
Access Control Lists are a fundamental component of Cisco networking, filtering traffic based on predefined rules. For CCNA and CCNP students, understanding the exact order in which a router processes packets against an ACL — not just how to write one — is what separates a memorized configuration from a genuine understanding of why a...
How to Configure Standard ACLs to Secure VTY Ports
Cisco routers and switches don’t allow meaningful remote access out of the box — VTY lines need at least a password configured before any Telnet or SSH session succeeds at all. Remote connectivity options are Telnet, over the VTY port, or SSH. SSH provides encrypted sessions and is strongly recommended by Cisco for remote administration,...