Obihai OBi110 Administration Manual page 15

IP Routing and LAN Switching Features (OBi202 Only)
OBi202 has two Ethernet ports labelled as the Internet port and the LAN port. The OBi works as a router by default. All the
native voice services and features use the WAN port only when the OBi202 is in router mode. The OBi can also be set to
work as a 3-port switch (a.k.a. Bridge mode), by changing its OperationMode parameter from Router to Bridge. Note: One
of the switch ports is for OBi202 internal use only.
IP Routing Features
In router mode we refer to the network connected to the OBi Internet Port as the WAN side of the OBi202, and the network
connected to the OBi LAN Port the LAN side of the OBi. The WAN side may be connected to another Ethernet switch or
directly to an access device such as a cable or DSL modem for Internet access. The OBi202 routes traffic between the LAN
side and the WAN side, thus allowing the devices (such as PCs) attached to the LAN side to share Internet access. The
OBi202 supports subnet masks as big as 255.255.255.0 to accommodate up to 253 IP addresses on its LAN side subnet.
In addition to being a NAT (Network Address Translation) router, the OBi202 includes a DHCP server, a DNS forwarder and a
basic firewall. It supports port forwarding, DMZ, QoS, and VLAN (802.1q). The maximum routing throughput between the
WAN and the LAN side is approximately 30 Mbps. This speed can be achieved when there are no active calls in the system.
Otherwise the throughput will be limited to a slower speed to accommodate the load for voice processing. Note that if the
WAN side is connected to an Internet access device directly, then the throughout could be further limited by the speed of
the Internet uplink and downlink.
The OBi202 will acquire its WAN side IP address using one of the following methods: Static Address Assignment, DHCP, or
PPPoE. By default, the OBi202 acquires its WAN side IP address using DHCP. Also by default, the OBi202's own DHCP server
is enabled to support LAN side clients, e.g. PCs. The default LAN side IP address of the router is 192.168.10.1.
Incoming packets receiving from the WAN side are forwarded by the router according to the following flow:

If firewall is enabled, discard the packet if it is rejected by any one of the active firewall components

If the sending host address matches a valid entry in an internal host binding table, queue the packet for local
processing. This binding table is updated by the router with an internal algorithm.

If the sending host address matches a valid entry in an internal NAT binding table, forward the packet to the
corresponding LAN IP address. The NAT binding table is updated by the router with an internal algorithm.

If the receiving port and protocol matches a reserved pair to support an internal process (e.g. TCP Port 80 for the
OBi202 web server process), queue the packet for local processing.

If the receiving port and protocol matches a port forwarding rule, forward the packet to the LAN IP address
according to that rule.

If a DMZ host is configured, forward the packet to that LAN IP address.

Queue the packet for internal processing.
DHCP Server
By default, the built-in DHCP server is enabled on the OBi202. It assigns IP address, network mask, DNS server and default
gateway address to the DHCP clients on the LAN side. The default gateway and DNS server have the same IP address as the
LAN side IP address of the router. In the DHCP server configuration, you may select the range of client IP addresses to give
out the Lease Time and the Local Domain Name. Furthermore, by using the DHCP reservation feature, you may reserve
specific IP addresses for some devices with specific MAC addresses. With this, those devices can always be assigned the
same IP addresses reserved for them each time they make a request to the DHCP server. See the LAN Settings and DHCP
Reservation sections for more details.
Copyright 2010-2012 Obihai Technology, Inc. 15