Preface:
In this document, I will explain many different routing protocols and give some
basic details and features about them. This document should in no way be considered
a source of complete details on any of the listed protocols. for detailed
information on routing protocols, I’d suggest looking at Request for
Comments (RFCs) for that protocol, watching them with open eyes, or perhaps visiting different
websites of providers such as Cisco, Juniper or Bay Networks. The website of most sellers
the sites have detailed explanations about all the protocols that there are teams
support features. Before you can understand the routing protocol, you will need to
have basic knowledge of IP networks, Variable Length Subnet Masks (VLSM),
Network topologies (bus, star, hub, etc.), and the OSI model. If you’re not
familiar with any of the above topics, you may want to read and learn about
before moving on to the routing protocols. Routing protocols are what make the
The Internet works by moving traffic from one network to another. no routing
Internet protocols could not work because the networks would simply be separated
LAN without connection to other LANs. Internet in basic terms is just a
many LANs connected together to form one huge WAN.
Protocol Types:
Distance vector: Distance vector routing is a type of
routing protocol that discovers routes in interconnected networks. Distance
The vector routing algorithm is based on the Bellman-Ford algorithm. Examples of
Distance vector routing protocols include Routing Information Protocol (RIP),
Cisco IGRP (Internet Gateway Routing Protocol) try Google to see all the
different protocols in the family of distance vectors. The distance vector protocols are
suitable for smaller networks as many of the protocols in this family are not
scalable in more complex networks since they are limited. The main limit of
In distance vector protocols there is a method that requires each router to simply
inform your neighbors of your routing table. This routing table is updated to other
members are bandwidth intensive for larger networks.
RIP (Routing Information Protocol):
Routing Information Protocol (RIP) is one of the first protocols used in
networks and is classified as a distance vector routing protocol. RIP-uses
transmit User Datagram Protocol (UDP) data packets to exchange routing
information. There are two RIP versions V1 and V2. RIP Version 1 is the original
version and has many limitations. The metric that RIP uses to qualify the value of
different paths is the hop count. The hop count metric works by assigning static
routes with a value of 0 and all other router values are set by the number of
hops (up to 15) that data must travel to reach an end point. RIP
Version 2 supports plain text and MD5 authentication, route summary,
Classless Inter-Domain Routing (CIDR), Variable Length Subnet Masks (VLSM),
Multicast support. Some vendors support other non-standard features for RIP purposes
be careful as many vendor centric features are not supported in a mixed vendor
the net.
IGRP (Intergateway Routing Protocol):
Interior Gateway Routing Protocol (IGRP) is a distance vector routing protocol
which is proprietary and invented by Cisco. Routers use it to exchange
data routing within an autonomous system (AS). IGRP supports multiple metrics
for paths, including bandwidth, load, delay, and MTU. This improves reliability
over RIP because IGRP uses advanced metrics to compare two routes in one
combined path. The two paths together are combined into a single metric, using
a formula that can be adjusted via the command line. The maximum number of IGRP hops
is 255, which is an improvement over 15-hop maximum RIPs. Note that IGRP is a
Cisco proprietary protocol and cannot be used in a mixed vendor network.
Link Status: The Link State routing protocol requires that each
router (peer) to maintain at least a partial map of the network. When a network
link changes state (from up to down, or vice versa), a notification, called link
The state advertisement (LSA) is flooded throughout the network. all routers
Please note the change and recalculate your routes accordingly. This method is more
reliable, easier to debug, and requires less bandwidth than distance vector. It’s
it is also more complex and requires more computation and memory. link state routing
The protocols are found in many larger networks and provide scalable solutions for
more complex networks.
OSPF (Open Shortest Path First):
Open Shortest Path First (OSPF) is a link-state routing protocol that requires
sending link-state advertisements (LSAs) to all other routers within the
same hierarchical area or autonomous system (AS). An AS can be divided into a
number of areas, which are groups of contiguous networks and attached hosts.
Information about attached interfaces, metrics used, and other variables are
included in OSPF LSA. As OSPF routers accumulate link-state information,
use the SPF algorithm to compute the shortest path to each node.
(IS-IS) Intermediate System to Intermediate System:
Intermediate System to Intermediate System (IS-IS) is a routing protocol
developed by the ISO and is natively an ISO connectionless network service or
CLNS protocol so it does not use IP to carry routing information messages. It’s
uses OSI protocols to deliver its packets and establish its adjacencies. EN-EN
has been enhanced to carry IP (Internet Protocol) and this is called Integrated
IS-IS. Integrated IS-IS supports VLSM and converges quickly. It is also scalable
to support very large networks and is the key protocol at many larger ISPs.
Hybrid: Hybrid routing protocols are a combination or
the distance vector and link state protocols and only one protocol fits into
this field. EIGRP is a Cisco Systems proprietary protocol based on its original
IGRP. For more information on hybrid protocols, see the “EIGRP” section below.
EIGRP (Enhanced Gateway Routing Protocol):
Enhanced Inter-Gateway Routing Protocol (EIGRP) is proprietary to Cisco Systems.
protocol based on its original IGRP. EIGRP is balanced hybrid IP routing.
protocol, with optimizations to minimize both the routing instability incurred
after topology changes, as well as the use of bandwidth and processing power in
the EIGRP router has protocol-dependent modules that can handle AppleTalk
and IPX in addition to IP. The advantage of this is that only one routing process
you need to run instead a routing process for each of the protocols. EIGRP provides
loop-free operation and near-instantaneous simultaneous synchronization of routers.
Inter-autonomous System: The routing protocols of the Inter-autonomous System are designed
to connect larger networks or Autonomous Systems (AS) with each other and allow
Multiple Autonomous Systems to the network. An example of the need for a
The protocol of the inter-autonomous system is to connect two or more Internet services.
Providers (ISPs) together so that customers can connect with each other. Without
going into too much detail, both “Link State and Distance Vector” protocols are
considered protocols of intra-autonomous systems, since they are designed to route
traffic in a single AS. The main objective of the protocols of the Inter-autonomous System is
distribute the information of the intra-autonomous system between different
systems
BGP4 (Border Gateway Protocol version 4):
Border Gateway Protocol is the primary routing protocol for most
Internet and allows the connection of peer networks and operators. BGP is
explained as a route vector protocol. With BGP, the policy or attributes for
make the actual route selections between the interconnected autonomous systems
is based on weight, local preference, multiple output discriminator, origin, AS route,
Next jump and community. BGP information is propagated through the network using
BGP message exchanges (4 types: Open, Update, Notification and Keep Alive)
Among partners. Another key feature of BGP is that it supports Classless Inter
Domain routing (CIDR) with BGP CIDR support can reduce the size of the
Internet routing tables. BGP neighbors exchange complete routing information when
first the TCP connection (port 179) between neighbors is established. When
augmented routing table changes, BGP routers send to their neighbors
only those routes that have changed. BGP routers do not send periodic routing
updates and advertises only the optimal routes to a destination.