Networking Grymoire

Networking Grymoire

Random tidbits that I need to reference every now and then. Everything is assumed linux

DNS

Dig

A lookup, going from name to ipv4 address

dig A @<dns server, preferably 8.8.8.8> <name>

Reverse lookup, going from ip address to name

# both are valid
dig -x 1.2.3.4
dig 4.3.2.1.in-addr.arpa

The key to look at the header sections for a better idea of what to do. For this header, we see ‘ANSWER: 1’. This is good! This tells us that there is an answer

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 260
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

If we shoot a dig request to a non-existent dns name, we get the following. The status is ‘NXDOMAIN’.

;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 14234
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

To find the authoritative servers, shoot an SOA request (start of authority) instead of a regular A request.

nslookup

if you want all the records for a dns name

nslookup -type=any www.yahoo.com

for a certain type of record

nslookup -query=ns www.yahoo.com

traceroute things

mtr

mtr <ip address>

firewall

ufw

// allowing a new rule ufw allow 8080/tcp

// where are those dang rules? sudo find / -type f -iname ‘userrules’ -ipath ‘ufw*’

// defaults ufw allow ssh ufw default deny incoming ufw default allow outgoing ufw enable

ip things

ip route

// List all routes ip route list // Set a new default route ip route add default via 192.168.1.1 dev eth1 // Check what interface we use for a given destination ip route get 8.8.8.8