Routing

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Revision as of 19:22, 28 June 2012 (edit)
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(A small bit about link-local addresses - more)
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clientB clientA clientB clientA
-Set the ([http://en.wikipedia.org/wiki/Private_network private]) [http://en.wikipedia.org/wiki/Subnetwork ip (sub)networks] to e.g.:+Set the ([[wikipedia:Private_network private|Private_network private]]) [[wikipedia:Subnetwork|Subnetwork ip (sub)networks]] to e.g.:
* apA 10.0.0.1/24 Short for: ( address 10.0.0.1 subnet 10.0.0.0 mask 255.255.255.0 = 24 left-to-right binary ones ) * apA 10.0.0.1/24 Short for: ( address 10.0.0.1 subnet 10.0.0.0 mask 255.255.255.0 = 24 left-to-right binary ones )
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==When private internet IPv4 addresses are used on the LAN (normally)== ==When private internet IPv4 addresses are used on the LAN (normally)==
-The following (NAPT; network address and port translation) is a necessary because of to few public internet IPv4 addresses. NAPT is commonly referred to as NAT ([http://en.wikipedia.org/wiki/Network_address_translation Network address translation]).+The following (NAPT; network address and port translation) is a necessary because of to few public internet IPv4 addresses. NAPT is commonly referred to as NAT ([[wikipedia:Network_address_translation|Network address translation]]).
The NAPT is normally done by a router or firewall with NAPT functionalty. The NAPT is normally done by a router or firewall with NAPT functionalty.
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* 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) * 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
-Note: Private ip addresses must be (source) translated ([http://en.wikipedia.org/wiki/Network_address_translation NAT]ted, tcp, udp: [http://en.wikipedia.org/wiki/Port_address_translation PAT]) to a public (=nonprivate) ip address (tcp: [http://en.wikipedia.org/wiki/Internet_socket socket]) before its payload can be send into the (public) internet.+Note: Private ip addresses must be (source) translated ([[wikipedia:Network_address_translation|NAT]]ted, tcp, udp: [[wikipedia:Port_address_translation|PAT]]) to a public (=non-private) ip address (tcp: [[wikipedia:Internet_socket|socket]]) before its payload can be send into the (public) internet.
==A small bit about link-local addresses== ==A small bit about link-local addresses==
-The [http://en.wikipedia.org/wiki/Link-local_address link-local addresses] ([http://tools.ietf.org/html/rfc5735 rfc5735]) ought not to be used as private addresses - but it can be used as private addresses and be NATted:+The [[wikipedia:Link-local_address|link-local addresses]] ([http://tools.ietf.org/html/rfc5735 rfc5735]) ought not to be used as private addresses - but it can be used as private addresses and be NATted:
* 169.254.0.0/16 * 169.254.0.0/16

Revision as of 19:29, 28 June 2012

Contents


start

This is the WIP page for routing with ddwrt. Just to have something to start.


In general router works like this:

  apB--------apA-----Internet (WAN) connection
    |              |
clientB      clientA

Set the (Private_network private) Subnetwork ip (sub)networks to e.g.:

  • apA 10.0.0.1/24 Short for: ( address 10.0.0.1 subnet 10.0.0.0 mask 255.255.255.0 = 24 left-to-right binary ones )
  • clientA 10.0.0.12/24 Short for: ( address 10.0.0.12 subnet 10.0.0.0 mask 255.255.255.0 )
  • apB 192.168.168.1/24 Short for: ( address 192.168.168.1 subnet 192.168.168.0 mask 255.255.255.0 )
  • clientB 192.168.168.15/24 Short for: ( address 192.168.168.15 subnet 192.168.168.0 mask 255.255.255.0 )

Routing (static) configurations:

  • tell clientA that apA is his default gateway (normally done through dhcp)
  • tell clientB that apB is his default gateway (normally done through dhcp)
  • tell apB that apA is his default gateway
  • tell apA that "WAN"-router is his default gateway
  • set the apB device to router mode
  • tell apA that requests to 192.168.168.0/24 will be routed through (apB) 192.168.168.1/24 (static route)

That's it!

When private internet IPv4 addresses are used on the LAN (normally)

The following (NAPT; network address and port translation) is a necessary because of to few public internet IPv4 addresses. NAPT is commonly referred to as NAT (Network address translation).

The NAPT is normally done by a router or firewall with NAPT functionalty.

The allowed private addresses are specified in rfc1918:

  • 10.0.0.0 - 10.255.255.255 (10/8 prefix)
  • 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
  • 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

Note: Private ip addresses must be (source) translated (NATted, tcp, udp: PAT) to a public (=non-private) ip address (tcp: socket) before its payload can be send into the (public) internet.

A small bit about link-local addresses

The link-local addresses (rfc5735) ought not to be used as private addresses - but it can be used as private addresses and be NATted:

  • 169.254.0.0/16

IPv6 also has link-local addresses (rfc4193):

  • FC00::/7