Differences Between an Ethernet Hub or
Switch and a Broadband Router
Last updated: 8/23/01
What are the differences between an Ethernet hub or switch and a broadband
A. For an introduction to Ethernet hubs and
switches and their differences, see “What is the difference between an Ethernet
hub and switch?” at http://duxcw.com/faq/network/hubsw.htm.
Most broadband routers (“routers” for short) are a combination
Ethernet switch (or hub) and Network Address Translator (NAT; see below). They
usually include a Dynamic Host Configuration Protocol (DHCP)
server, Domain Name Service (DNS) proxy server (see below), and a hardware
firewall to protect the Local Area Network (LAN) from malicious intrusion
from the Internet.
All routers have a Wide Area Network (WAN) Port. This
port connects to the to a DSL or cable MODEM for broadband service (e.g.,
the Internet) and is usually a 10 MHz 10BASET Ethernet port. A 10 MHz
WAN port is sufficient for cable and DSL MODEMs as these devices transfer
data at rate that is a fraction of 10 MHz. I have seen no broadband
routers with a USB WAN port to connect to a USB cable or DSL MODEM.
Many recent broadband routers are combination routers/Ethernet
switch (or hub) that have multiple Ethernet ports to connect more than one
PC to form a LAN. These ports allow the PCs to share the WAN port/broadband
Internet connection and perform LAN functions, such as Windows file and printer
sharing. The LAN ports are usually 100 MHz 100 BASE-TX Ethernet.
Some routers have a single WAN port and a single LAN port
and are designed to connect to an existing LAN hub or switch to a WAN.
Ethernet switches and hubs can be connected to router with
multiple PC ports to expand a LAN. Depending on the capabilities (kinds
of available ports) of the router and the switches or hubs, the connection
between the router and switches/hubs may require straight-thru or crossover
cables (http://duxcw.com/digest/Howto/network/cable/cable1.htm). See
“What is an uplink port and what are the ways to connect two hubs/switches
together?” at http://duxcw.com/faq/network/uplink.htm for
Some routers have ports for USB connections to computers
on a LAN. Some have wireless LAN capabilities.
In addition to a WAN port, broadband routers, such as the
SMC Barricade routers (http://duxcw.com/digest/Reviews/Network/smc/smc7004br/smc7004br.htm),
may have a serial port that can be connected to an external dial-up MODEM
(useful as a backup for the cable of DSL service) and a built in LAN printer
server and printer port.
A router DHCP server provides local Internet Protocol (IP)
e.g., 192.168.02, 192.168,.0.2,…) to PC’s, etc. on the LAN set to obtain
their IP addresses automatically. These DHCP servers can usually be
configured to allow assignment of static IP addresses to PCs and other devices
on the LAN. A router-borne DNS proxy handles Internet name resolution
requests form PCs on the LAN to the ISPs DNS servers to translate names of
computers on the Internet to IP addresses (e.g., duxcw.com to 220.127.116.11). The
NAT function in the broadband router allows sharing a single IP address provided
by the Internet Service Provider with PCs connected directly to the router/switch
or to hub or switch connected to the router by mapping local LAN IP addresses
(assigned by the DHCP server or static IPs on the same TCP/IP subnet) to
Internet IP addresses and vice versa and translating the address information
in the TCP/IP protocol packets.
Besides the inherent protection features provided by the
NAT, many routers have a built-in, configurable, hardware-based firewall. Firewall
capabilities can range from the very basic to quite sophisticated. Among
the capabilities found on leading routers are those that permit configuring
TCP/UDP ports (http://www.iana.org/assignments/port-numbers)
for games, chat services, and the like, and installing web servers, etc.
on the LAN behind the firewall.
In short, a hub glues together an Ethernet network segment,
a switch can connect multiple Ethernet segments, and a router can do those
functions plus route TCP/IP packets between multiple PCs on LAN and a WAN,
and much more.