Transcript Routers - Ethernet Direct

Ethernet Basics – 8
Routers
Routers and Routing
• Definition of a router- A device which provides a path from a node on
one network or subnet to a node on another network
• Definition of routing- the process of determining and end-to-end path
between the sender and the receiver of a packet. There are 2 types:
– Source routing- the source node determines the route and
includes it in special fields in the data frame. Source route
bridging in Token Ring uses source.
– Hop-by-hop- The route between source and destination is
determined along the way, hop by hop. Most routing protocols
are hop-by-hop based.
• The routing protocols most used are RIP, RIPII and OSPF for
standard protocols. They will be discussed in greater detail during
the Routing/Layer 3 presentation
Routers
• A router has 2 main functions:
– Connect networks together
– Block broadcasts
• All the other functions that we have seen routers do are add-ons and
are not part of the root functionality
• For routers to learn where the different networks are located within
an area, a routing protocol is used to tell routers what network is off
what router. There are 2 ways to do this…
– Static- you manually script on each router where all the networks
are. This is very time and maintenance intensive
– Dynamic- the routing protocol itself learns the attached networks
and sends this information automatically between all the routers.
• Routing Table- This table holds all the IP/Network layer information
for the router much like the forwarding database on a switch holds
the layer 2 location information for end devices. It also called an
ARP cache for end device information.
Router- Network Layer
Broadcast Domain
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192.168.2.x
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192.168.1.x
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Broadcast Domain
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Broadcast Domain
Routers divide broadcast
domains
And
connect networks
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192.168.3.x
255.255.255.0
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Thank You
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