Handout 6 Flashcards
These routes are manually configured by network administrators, have low system requirements, and apply to simple, stable, and small networks. The disadvantage of static routes is that they cannot automatically adapt to network topology changes and so require manual intervention
static routes
are used only when packets to be forwarded do not match any routing entry in an IP routing table.
default routes
On the Internet, routers need to exchange routing information in the interconnection of networks called
autonomous systems (AS or domains)
The autonomous systems are connected together in the form of a network called
core network (backbone)
meant to dynamically route data across a network that you fully control and maintain. Basically, interior protocols are meant to dynamically route data across a network that you fully control and maintain
interior gateway protocol (IGP)
used to exchange routes between distinctly separate networks that you have no administrative control over. BGP is the routing protocol used on the Internet; therefore, the most common enterprise use is to run BGP on your internet edge when connecting to your ISP
exterior gateway protocol (EGP)
determine good paths (routes) from senders to receivers through the network of routers
routing algorithms
finds a path between the source and destination with the least cost
least-cost path
path with the smallest number of links between the source and the destination
shortest path
In this type of routing, all the routers send their neighboring routers
distance-vector routing protocol
a commonly used distance vector routing that uses its routing metric to determine the best route or shortest path a packet has to traverse from the source to a destination over a network. RIP is a distance-vector IGP and has a preference of 100
routing information protocol (RIP)
number of routers through which a packet passes to reach its destination
hop count
In this type of routing, each of the routers sends the state of its own interfaces to all other routers only when there is a change to report. Each router uses the received information to recalculate the best path to each network and then saves this information in its routing table
link-state routing protocol
description of the router interface
link-state (LS)
the cost of sending data packets on the interface, expressed in the link state metric.
output cost
these are other routers that are attached through the link-state
list of neighboring routers
an OSPF data packet containing link-state and routing information that is shared with the other routers
link-state advertisement (LSA)
a unit of data describing the local state of router’s interfaces and adjacencies. The collected LS advertisements of all routers and networks form the LSDB
link-state PDU
a collection of all LS PDUs originated from the area’s routers. Each router advertises directly connected networks via LS POU.
link-state datebase (LSDB)
a link-state routing protocol develope by the IETF in 1988 that is capable of quickly detecting topological changes within the autonomous system and establishing loop-free routes in a short period of time, with minimum additional communication overhead for negotiating topology changes between peering routers
open shortest path first (OSPF)
a special data packet (message) that is sent out periodically from a router to establish and confirm network adjacency relationships to other routers in the OSPF
HELLO packet
contains information, such as the destination IP address, cost, and next-hop IP address, which guides packet forwarding
OSPF routing table
is the ISO name for a router, it is the communication between intermediate systems or routers
intermediate system (IS)
a device on the network, such as a server or workstation (hosts)
end system (ES)
a network service in the OSI stack
connection-less network service (CLNS)
a layer-3 address for CLNS packets, this is like an IP address in the TCP/IP stack. IS-IS uses this to address for communication not IP addresses
network service access point (NSAP)
a router in a normal area that does not connect to another area (red)
level 1
a backbone router that does not connect to other areas (green)
level 2
a router in a normal or backbone area that connects different areas (blue)
level 1-2
