Routing

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(When private internet IPv4 addresses are used on the LAN (normally) - more)
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(When private internet IPv4 addresses are used on the LAN (normally) - chg)
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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.
 +
 +==A small bit about link-local addresses==
The link-local addresses ([http://tools.ietf.org/html/rfc5735 rfc5735]) ought not to be used as private addresses: The link-local addresses ([http://tools.ietf.org/html/rfc5735 rfc5735]) ought not to be used as private addresses:
* 169.254.0.0/16 * 169.254.0.0/16
Line 43: Line 46:
IPv6 also has link-local addresses ([http://tools.ietf.org/html/rfc4193#section-3 rfc4193]): IPv6 also has link-local addresses ([http://tools.ietf.org/html/rfc4193#section-3 rfc4193]):
* FC00::/7 * FC00::/7
- 
-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. 
[[Category:Routing| ]] [[Category:Routing| ]]

Revision as of 19:13, 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) 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 (sNAT) is a necessary because of to few public internet IPv4 addresses.

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 (=nonprivate) 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:

  • 169.254.0.0/16

IPv6 also has link-local addresses (rfc4193):

  • FC00::/7