Routing tables

From wikinotes

routing tables are used whenever you try to communicate with a network.
they store a default route, and gateways to access known networks.

Basics

Generally store at least this info:

destination network:   192.168.1.0/24   # network you want to reach

next hop:              10.0.0.0/24      # to reach dest network, communicate with this netwk

total hops:                             # number of networks to communicate to reach network. 
                                        # updated periodicaly to ensure we take quickest route

interface:             em0              # which network interface should be used for next hop?

example FreeBSD routing table


netstat -r
Routing tables

Internet:
Destination        Gateway            Flags     Netif Expire
default            unifi.localdomain  UGS         em0
10.0.0.0/24        link#5             U       wg-salt
10.0.0.1           link#5             UHS     wg-salt
10.0.0.8           link#5             UHS         lo0
localhost          link#3             UH          lo0
192.168.1.0/24     link#1             U           em0
192.168.1.201      link#1             UHS         lo0

Internet6:
Destination        Gateway            Flags     Netif Expire
::/96              localhost          UGRS        lo0
localhost          link#3             UHS         lo0
::ffff:0.0.0.0/96  localhost          UGRS        lo0
fe80::/10          localhost          UGRS        lo0
fe80::%lo0/64      link#3             U           lo0
fe80::1%lo0        link#3             UHS         lo0
ff02::/16          localhost          UGRS        lo0


example Linux routing table


netstat -r
iKernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
default         _gateway        0.0.0.0         UG        0 0          0 wlp3s0
10.0.0.0        0.0.0.0         255.255.255.0   U         0 0          0 wg-salt
172.17.0.0      0.0.0.0         255.255.0.0     U         0 0          0 docker0
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlp3s0

Tools

FreeBSD route
net-tools route