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DTUS065 rev A.7 – June 27, 2014
V.1.3.2
Routers (a.k.a. gateways)
Each network device communicating through routers MUST know the IP
address of the gateway nearest to it. It will use this gateway to forward data
to farther LANs. If a device does not know its gateway, it may receive data
but may not return an answer. For example this can forbid answering a
PING even if the PING request makes its way to the device.
When several routers are available on a single LAN to access various remote
LANs, the network devices on the LAN should know about each router’s
own address and the remote network addresses they lead to. Usually one of
the routers is designated as “default”, the other ones are treated as
exceptions to this default route.
Network devices often use the DHCP protocol to get their IP address. The
DHCP server may provide the address of the local router at the same time.
V.1.3.3
Zones
In a router, you may need to selectively block or allow traffic between
network interfaces. A zone is an administrative concept which groups
several IP interfaces in order to specify common extra processing:
•
Firewall rules
•
IP address conversion rules (to implement NATs).
10.1.2.30
Default
gateway
10.1.2.1
Subsidiary
gateway
Subsidiary’s LAN
192.168.1.x/8
Public IP
10.1.2.25
192.168.1.25
192.168.1.26
Internet
Main LAN (Wi-Fi)
10.x.x.x/24
Device #2 must know about
address 192.168.1.25, to
send to device #1
Device #2
192.168.1.12
Device #1 must know about
address 10.1.2.1 to send to
device #2
Device #1
10.1.2.30
Internet
Gateway
#1
10.1.2.1
Gateway
#2
192.168.1.25
LAN1:10.x.x.x
LAN2:192.168.1.x
