Information Technology Reference
In-Depth Information
A distance vector router only knows
The direction or interface in which packets should be forwarded
■
The distance to the destination network
■
Operation of Distance Vector Routing Protocols
Some distance vector routing protocols call for the router to periodically
broadcast
the entire
routing
table
to each of its neighbors. This method is inefficient because the updates not only consume net-
work
bandwidth
but also consume router
CPU
resources to process the updates.
In reference to routing protocols, what is a neighbor?
Neighbors are routers that share a link and are configured to use the same routing protocol.
Broadcast updates are sent to
255.255.255.255
(IP address). Neighboring routers that are configured
with the same
routing protocol
will process the updates. All other devices will also process the update
up to Layer
3
before discarding it.
At the core of the distance vector routing protocol is the
algorithm
used to calculate the best paths and
then send that information to the neighbors.
Routing Protocols Characteristics Exercise
Briefly explain each of the following routing protocol characteristics.
Time to convergence
Time to convergence defines how quickly the routers in the network topology share routing informa-
tion and reach a state of consistent knowledge. The faster the convergence, the more preferable the
protocol. Routing loops can occur when inconsistent routing tables are not updated because of slow
convergence in a changing network.
Scalability
Scalability defines how large a network can become based on the routing protocol that is deployed.
The larger the network is, the more scalable the routing protocol needs to be.
Classless (use of VLSM) or classful
Classless routing protocols include the subnet mask in the updates. This feature supports the use of
variable-length subnet masking (VLSM) and better route summarization. Classful routing protocols do
not include the subnet mask and cannot support VLSM.
Resource usage
Resource usage includes the requirements of a routing protocol, such as memory space, CPU utiliza-
tion, and link bandwidth utilization. Higher resource requirements necessitate more powerful hard-
ware to support the routing protocol operation in addition to the packet-forwarding processes.
Implementation and maintenance
Implementation and maintenance describe the level of knowledge that is required for a network
administrator to implement and maintain the network based on the routing protocol deployed.
