Notes about Your Router Features

In addition to the features described below, your router includes an integrated print server, allowing you to share your USB printer with other computers on your network and a 4-Port Ethernet switch for connecting Ethernet devices.

Firewall - Stateful Inspection

The U.S. Robotics ADSL 4-Port Router provides firewall stateful inspection for intrusion detection. The router tracks all packets originating from the LAN and records each connection's address pair and the TCP/UDP port pairs. When receiving TCP/UDP packets from the Internet, the IP addresses and port numbers must match the tracking records. Otherwise, the router drops the packet.

For ICMP packets, only outgoing ICMP request packets originating from the LAN are forwarded to the Internet, and its related incoming ICMP reply packets from the WAN side are allowed to come into the LAN. For example, you can ping any device on the Internet from a computer on the LAN, but you cannot ping the router or any LAN device from the Internet.

Also, the router does not let ICMP redirect packets in, since they could be used to reroute traffic through attacking machines. The only exception to the above firewall rules occurs when remote technical support access is explicitly allowed by the local user. The router then responds to ping request packets and allows remote access to the router's Web User Interface (WUI). The router firewall also prevents LAND attacks and SYN floods:

• SYN floods: the router firewall drops all unsolicited TCP SYN requests received from the Internet.
• Land attacks: this type of attack forces a victim machine into an unending loop. The router firewall can prevent such attacks by disallowing any packets with the same source and destination address.

Security - Remote and Local Access Accounts

• The U.S. Robotics ADSL 4-Port Router WUI provides a local admin account, a local non-administrative user account, and a remote technical support account, all with password protection. The support account allows the local administrative user to explicitly let a remote technician access the router's WUI.
• The user account can view the configuration parameters but not change them.
• The support account does not work in bridge mode since there is no public IP address assigned to the router.
• The remote technical support user can read/write the configuration but cannot change security settings. When remote access security is enabled by a local administrator, the remote user can access the modem via telnet or a browser from the Internet, but not from the LAN.
• The maximum length for passwords is 15 characters.

DHCP Server

The router provides DHCP server service over the LAN interface when the network operating mode is set to PPPoE, PPPoA, MER or IPoA mode. When enabled, the DHCP server responds to DHCP request packets from LAN devices and assigns:

• An unused IP address within the start-end IP address range configured by the user to the LAN device.

• The router's LAN interface IP address as the primary DNS server address to the LAN device. The ADSL router performs DNS relay between the LAN device and the real DNS server at the remote service provider site.

• The router's LAN interface IP address as the default gateway to the LAN device.

DHCP Client

The router provides DHCP client service for each Internet interface operating in the MER network operating mode. If enabled, the DHCP client requests the WAN interface IP address, primary and secondary DNS server addresses, and default gateway from the DHCP server at the service provider site. If the DHCP client function is disabled, the user must manually configure the WAN IP address, DNS server addresses and default gateway.

DNS Relay

The router provides DNS Relay service only when the NAPT function is enabled. It forwards the DNS inquiry packets received from the LAN devices to the primary DNS server at the remote site and vice versa. The DNS response packets received from the remote DNS server are relayed back to the LAN device. (Click here for more information about NAPT.)