Routing

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Revision as of 19:29, 28 June 2012 (edit)
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That's it! 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 ([[wikipedia:Network_address_translation|Network address translation]]). 
- 
-The NAPT is normally done by a router or firewall with NAPT functionalty. 
- 
-The allowed private addresses are specified in [http://tools.ietf.org/html/rfc1918 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 ([[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==

Revision as of 19:35, 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!


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