How to find your IP address
Do lookups online

Network tools

Network utilities. Some may be disabled on your setup.

Linux / UNIX

To see IP address:
1. ifconfig (older tool) (not on DCU server)
2. ip (newer).
3. Usage: How to find your IP address
To query who owns domain, does host exist
1. dig (domain or host)
2. host (like dig but returns less info)
3. nslookup (hostname)
4. netstat
5. whois (domain)
  - whois dcu.ie reveals DCU nameservers (for external users):
```
Name Server: ns-105.awsdns-13.com
Name Server: ns-1250.awsdns-28.org
Name Server: ns-2005.awsdns-58.co.uk
Name Server: ns-870.awsdns-44.net
```
    We use Amazon Web Services DNS service.
Other tools:
1. ping (send packet to see if host is up) (think only works locally at DCU)
  - To just ping once:
```
 ping -c 1 hostname 
```
2. traceroute (query route to host)
  Think not working since DCU changed to Amazon services.

Exercise

Look up who owns yahoo.com
Look up who owns the "typo" yahooo.com
What is the smallest number of o's before someone outside Yahoo owns the domain?
What is the smallest number of o's before no one owns the domain?
See Typosquatting

Windows

Windows command line
- Reference
To see your IP address:
1. ipconfig
  - ipconfig /all shows DNS servers.
  - How to find your IP address
Tools:

Traceroute

It used to be easy to use traceroute to see routes to distant servers.
Seems to be getting harder to use it. Traceroute blocked by firewalls / never returns.
Search for traceroute online lookup.
Comms from DCU to UCD go through HEAnet.

Here is an old traceroute from DCU to UCD, before Amazon was contracted:

$ traceroute www.ucd.ie
traceroute to www.ucd.ie (193.1.172.140), 30 hops max, 40 byte packets
 1  router-11.computing.dcu.ie (136.206.11.254)  0.383 ms  0.247 ms  0.330 ms
 2  136.206.13.254 (136.206.13.254)  0.369 ms  0.303 ms  0.344 ms
 3  cisdcu.dcu.ie (136.206.3.1)  0.813 ms  0.670 ms  0.362 ms
 4  kuiper-gige2-1.dcu.access.hea.net (193.1.196.189)  1.356 ms  1.098 ms  1.508 ms
 5  hyperion-gige4-2.cwt.core.hea.net (193.1.194.68)  1.558 ms  1.602 ms  0.990 ms
 6  ar1-cwt-gige6-1.hea.net (193.1.195.177)  1.824 ms  1.466 ms  1.918 ms
 7  * * *
 8  nore-r2-vlan-13.ucd.ie (193.1.145.10)  2.667 ms  2.737 ms  2.647 ms
 9  clarion.ucd.ie (193.1.172.140)  2.299 ms  2.573 ms  2.339 ms

Visual TraceRoute used to work.
Here is an old trace from US server outwards.
Transatlantic link may be ocean floor cable or may be satellite.