Network Devices

Hub Hubs operate at layer 1 of the OSI model. A hub sees a signal come in and broadcasts that signal out every port except the one it came in on. Hubs are really obsolete at this point in time, and I would personally never pay for/use one, but I wouldn’t imagine a hub costing more than $50.

Ethernet hub

Switch A switch operates at layer 2 of the OSI model traditionally. This being the case, each port on the switch is it’s on collision domain. The price of a switch varies greatly based on port density, speed, etc. Switches can go anywhere from $40 up to Tens of thousands of dollars like the switches I manage.

Cisco Nexus 7010

Router A router operates at layer 3 of the OSI model, and forwards IP packets based on destination IP address. A router separates broadcast domains. Routers range in price from $50 for a consumer router all the way up in to the millions like the routers I manage.

Cisco CRS 3 router and RLCs

Bridge A bridge allows the aggregation of multiple networks. I have not personally used a Network Bridge, and would assume that few do anymore, as bridging seems obsolete since the introduction of the .1q header/VLAN tagging which allows link aggregation/the security of segregation of broadcast domains at layer 2, even when utilizing the same physical link. Bridges operate at layer 1 & 2 of the OSI model.

Bridge

Gateway A gateway is a device that separates networks. The Most common example of a gateway would be a router. A computers default gateway would be the first layer 3 hop (first router) that IP packets destined for a different IP subnet must traverse.

Gateway: Cisco CRS 3 Router

Firewall Modern day firewalls operate at layer 3 and 4 of the OSI model and are considered stateful; that is, they maintain a session state table, so that once the TCP three way handshake occurs (syn, syn ack, ack) bidirectional traffic flow is permitted unless the TCP session times out. Firewalls perform packet inspection based on Source/dest IP and port typically. Firewalls range greatly in price; from free (included in your router) to Hundreds of thousands like the ones I manage.

Juniper SRX 5800

Wireless access point A wireless access point allows a wifi enabled client access to a network or the internet. In an enterprise environment, WAPs are typically plugged in to a switch or controller. A controller is a means of managing a large number of WAPs, seamlessly. In an enterprise environment, a WAP is normally not responsible for the assignment of an IP address to the client. Rather, the router or DHCP server in the same network segment is typically responsible for assignment of IP address.

Cisco 1252AG