• Creating a Public DNS Server and advertising an Authoritative Domain

    Hi All, so you’ve probably heard of goDaddy.com to register DNS names publicly. However have you ever done a dig or nslookup on your registered name? It probably returns the name you queryied and the IP address just as you expected, however this is because dig is by default recusive. This means that it will ask it’s known DNS server if it knows the DNS resolution for your query, if not, forward it on and on and on until it is found through the DNS hiearchy or it times out. See the diagram below.

    DNS Hierarchy

    Let’s walk through this.

    • TLD (Top-Level Domains) — These are the highest level on the DNS hierarchy. You can find a list here.
    • SLD (Secondary Level Domains) — These are they domain names you are most familary with, like google.com, slashdot.org, thejimmahknows.com. Notice each of there suffix’s
    • Sub Domains — Logically grouped resources, such as mail.google.com and linux.slashdot.org. Can have multiple prefix subdomains (i.e. a.b.c.d.google.com)
    • Resource Records — There are several different types. The most common are A reocrds, MX records, and CNAME records.

    [Read More…]

  • Cisco IOS Router as a DHCP/DNS Authoritative Server

    I was trying to set up a SOHO router for a small client the other day and was having difficulty getting the DNS server to function the way I wanted on the router. I could get the DNS server to run on the Cisco Router, but it would only work on external domains. Any static record I added would not be resolvable for clients.

    For starters, I will assume you have your own Cisco router running 12.4+ IOS firmware with ipservices.

    DHCP first…

    1. First, let’s set up DHCP on the Router
      R1(config)# interface fastEthernet 0/1
      R1(config)# ip address
      R1(config)# no shutdown
    2. Enable DHCP service on that interface
      R1(config)# ip dhcp-server
    3. Configure DHCP settings
      R1(config)# ip dhcp pool dhcp-pool
      R1(config-dhcp)# network
      R1(config-dhcp)# domain-name yourdomain.local
      R1(config-dhcp)# dns-server
      R1(config-dhcp)# default-router
      R1(config-dhcp)# lease 7

      [Read More…]