Hi,
A Bridge is a layer2 Device and is only concerned with Ethernet Frames.
Your every-day switch, such as Cat2960 is a bridging device.
Basically, when a frame enters a bridge (or a port on a switch) the destination MAC address is looked up in the CAM or MAC-Address table, to see where that MAC address has been seen.
If an entry is found, then the frame is forwarded ONLY out the port that the MAC was seen on.
If no entry has been found in the CAM table, then the frame is forwarded out of every port.
A router is a Layer 3 device and routes packets. When a packet enters a router, the destination IP address is looked up in the routing table, and forwarded out of the relevant port. Most small office or home routers have only one route (0.0.0.0/0) which is called the default route, and this will usually point out to the internet. If there is no entry in the routing table that matches the destination IP address, and there is no default route, then the packet is dropped.
A gateway is just another word (Kind of) for a router. e.g. your PC will have a default gateway setting. That IP address will most likely be a router address.
Bridging a VLAN is the action of creating a layer 2 link between 2 VLANs. i.e. A frame sent on one VLAN would be recieved on the other.
--NOTE--
It is highly unlikely that you would ever need to do this. The reasons for doing so are very specific, and don't crop up very often.
--NOTE--
Routing a VLAN is the action of routing packets between two VLANs.
e.g.
VLAN1 has subnet 10.10.10.0/24
VLAN2 has subnet 10.20.20.0/24
A properly configured router will route packets between these vlans.
Please rate useful posts.
Nick
