When I'm connected to two networks with internet access, what exactly is happening as I use internet?

Question

I was just testing a little USB wifi dongle to see whether it's going to work with Raspberry PI. It seems ok on my windows machine. As we have two wifi networks at home, I used the dongle to connect to the second one which means now I'm connected to two internet providing networks.

This situation described above made me think and raise a question.

That question is: Does this have any effect on my internet speed? Does the computer switch over the networks or assign different connections different networks? My networks are both connected to same modem, sharing the actual maximum speed - but if I used completely different connection types, such as android bluetooth tethering and my home WiFi, would it speed up my connection?

Answer 1

By default, your computer will use one network path to reach destinations; which ever network connection has the lowest routing metric, which on a Microsoft Windows system you can see with the route print command.

You can modify that behavior by adding a specific route to a particular destination with the route add command. The syntax for the route add command can be viewed by issuing the command route /? at a command prompt on a Microsoft Windows system.

C:\>route /?

Manipulates network routing tables.

ROUTE [-f] [-p] [-4|-6] command [destination]
                  [MASK netmask]  [gateway] [METRIC metric]  [IF interface]

  -f           Clears the routing tables of all gateway entries.  If this is
               used in conjunction with one of the commands, the tables are
               cleared prior to running the command.

  -p           When used with the ADD command, makes a route persistent across
               boots of the system. By default, routes are not preserved
               when the system is restarted. Ignored for all other commands,
               which always affect the appropriate persistent routes.

  -4           Force using IPv4.

  -6           Force using IPv6.

  command      One of these:
                 PRINT     Prints  a route
                 ADD       Adds    a route
                 DELETE    Deletes a route
                 CHANGE    Modifies an existing route
  destination  Specifies the host.
  MASK         Specifies that the next parameter is the 'netmask' value.
  netmask      Specifies a subnet mask value for this route entry.
               If not specified, it defaults to 255.255.255.255.
  gateway      Specifies gateway.
  interface    the interface number for the specified route.
  METRIC       specifies the metric, ie. cost for the destination.

All symbolic names used for destination are looked up in the network database
file NETWORKS. The symbolic names for gateway are looked up in the host name
database file HOSTS.

If the command is PRINT or DELETE. Destination or gateway can be a wildcard,
(wildcard is specified as a star '*'), or the gateway argument may be omitted.

If Dest contains a * or ?, it is treated as a shell pattern, and only
matching destination routes are printed. The '*' matches any string,
and '?' matches any one char. Examples: 157.*.1, 157.*, 127.*, *224*.

Pattern match is only allowed in PRINT command.
Diagnostic Notes:
    Invalid MASK generates an error, that is when (DEST & MASK) != DEST.
    Example> route ADD 157.0.0.0 MASK 155.0.0.0 157.55.80.1 IF 1
             The route addition failed: The specified mask parameter is invalid.
 (Destination & Mask) != Destination.

Examples:

    > route PRINT
    > route PRINT -4
    > route PRINT -6
    > route PRINT 157*          .... Only prints those matching 157*

    > route ADD 157.0.0.0 MASK 255.0.0.0  157.55.80.1 METRIC 3 IF 2
             destination^      ^mask      ^gateway     metric^    ^
                                                         Interface^
      If IF is not given, it tries to find the best interface for a given
      gateway.
    > route ADD 3ffe::/32 3ffe::1

    > route CHANGE 157.0.0.0 MASK 255.0.0.0 157.55.80.5 METRIC 2 IF 2

      CHANGE is used to modify gateway and/or metric only.

    > route DELETE 157.0.0.0
    > route DELETE 3ffe::/32

E.g., you could choose the network path that isn't the default one to reach a particular website, etc. by using a route add command and specifying the gateway address for the other path. In your case there would be little difference in the overall network path, since both paths lead to the same network device that provides access to the Internet.