When to use BGP |why use Border Gateway Protocol?

Why we use BGP?

GBP (Border Gateway Protocol) is mostly used by ISPs (internet service providers). BGP is replaced with the older protocol that is EGP and latest version of BGP is Version 4. BGP v4 is defined in RFC 1771 you can read that for more detail. BGP suppose to be a distance vector protocol, it metric is hop count but hop count in BGP case is a autonomous system therefore BGP is also know as path vector protocol.

GBP Border Gateway Protocol

As a routing protocol BGP is best choice in following environment:

  • BGP is normally use for connecting different AS’s, in an environment where your autonomous system have multiple links to other AS’s.
  • BGP is better option in transit AS, it mean that you can allow your packets packet to move through from one AS to other AS, for Example LAN to an ISP.
  • BGP is build for controlling the large networks, it will work great if you have a large amount of traffic and traffic needs high degree of control.
  • The multiprotocol version of BGP is used to carry MPLS VPN information between all provider edge (PE) routers within a VPN community. MP-BGP is defined in RFC 2858. It introduces a new BGP capabilities advertisement to determine whether a BGP peer supports MP-BGP.
  • You can handle the Policy-based routing with BGP among different AS. There two types of BGP that are IBGP and EBGP, you can use the IBGP in internal or in single AS, while EBGP is used among different AS.


When to use OSPF | why use Open shortest path first?

Why we use OSPF as a Routing Protocol?

OSPF works great in different WAN environments like  point to point, non broad cost multi-access, point to multipoint, frame-relay and in LAN environment. OSPF is also a great routing protocol for dialup scenarios and in heterogeneous organization which use to own different companies or business having with different vendors’ devices. In such environments OSPF is better choice because of it flexibility and following great features.

OSPF Open shortest path first

  •  Open shortest path first is design for replacement of RIP and support large and most complex networks. The most recent version of OSPF is version 3 that is defined is RFC 2740, which also have the IPv6 support. OSPF is open standard protocol, you can run OSPF among any vender.
  • OSPF has fast convergence and also have the option for tuning more metric values. OSPF support VLSM and is a better protocol for dialup.
  • In OSPF you can divide your network into different OSPF areas. The central or core area is known as backbone area and all other area must be connect to this backbone area. The idea behind the OSPF areas is to lower the amount of routing traffic and lower the processing of your core routers. Different areas are connected with each other through Area Border Router (ABR).
  • OSPF is link state routing protocol and you can tune a link state routing protocol to converge fast. Link state routing protocols send the periodic update via LSAs you can learn more about OSPF LSAs.
  • Metric is “OSPF cost” (based on interface bandwidth by default).
  • Default administrative distance for OSPF is 110.
  • With Cisco routers, OSPF also supports equal-cost multipath load balancing and neighbor authentication.
  • OSPF find the shortest path among the different areas using the dijkstra algorithm, ABR of each router calculate the roadmap/shortest path to each destination and send the only summary route to backbone.
  •  OSPF also offer the special area types like stub area, totally stub area and not so stubby area (NSSA). Using these area types you can minimize the LSAs in an area and also decide that which routing information should be injected into backbone or which are not.

Learn How to configure OSPF in packet tracer.

When to use EIGRP why use Enhance interior Gateway routing protocol?

why we use EIGRP?

Enhance interior Gateway routing protocol was a Cisco proprietary protocol, but this premise that EIGRP is a Cisco proprietary protocol does not hold true anymore. EIGRP is suitable to use in medium to large networks. Following are some key features for help you to choosing EIGRP as your routing protocol.


  •  EIGRP is an advanced distance-vector protocol that but some Cisco documentation refers to EIGRP as a hybrid protocol. Because EIGRP advertises its routing table to its neighbors as distance-vector protocols do, but it uses hellos and forms neighbor relationships as link-state protocols do.
  • VLSM is support by EIGRP.
  • EIGRP provide the fast convergence using the DUAL algorithm and easy to configure as compare to OSPF and ISIS.
  • EIGRP sends partial updates when a metric or the topology changes on the network. It does not send full routing-table updates in periodic fashion as do distance-vector protocols.
  • EIGRP has an administrative distance of 90 which is lower than RIP and higher than OSPF.
  • You can configure EIGRP for 255 Hops count that means you can use the EIGRP for large network.
  • EIGRP metric is EIGRP cost and normally depends on bandwidth on delay but you can tune EIGRP for other metric values as well.
  • In EIGRP route updates send every 90 seconds
  • EIGRP can send 104 routes per routing updates
  • EIGRP support authentications using this you enable the EIGRP among authorize routers.
  •  Equal cost load balancing is one of good feature of EIGRP but you can also enable the unequal cost load balancing.
  • EIGRP send routing updates to it multicast address on

EIGRP is suitable for almost all enterprise environments, included LANs and WANs and is simple to design. The only caveat is that it is a Cisco proprietary routing protocol which cannot be used with other vendors. The use of EIGRP is preferred over RIP in all environments.

Features of EIGRP Protocol & EIGRP Job Interview Questions

Test your knowlegde about routing protocols by taking Quiz: OSPF QuizIPv6 QuizRIP QuizEIGRP QuizNetworking Quiz

When to use RIP why use Routing information protocol?

RIP Features..!

Routing information protocol is most commonly deployed routing protocols, most of the operating windows, Linux and novel system use RIP. Routing information protocol is normally suitable for small office, medium office, branch office environment and flat networks. RIP is an interior routing protocol and used in inter-domain environment.  RIP have following three versions:

1.       RIPv1 (version 1)

2.       RIPv2 (version 2, VLMS and authentication support)

3.       RIP NG (new generation, support IPV6)


This article is related RIP design and we will study the features of RIP. Following are the important features of RIP those can be consider while choosing RIP for your network.

  •  RIP is distance vector routing protocol.
  • Administrative distance for RIP is 120 that is most highest among other dynamic routing protocols. Administrative distance represents how much a route is trusted, routing protocols with higher administrative distance are less trust among others. Support if a router has multiple paths to same destination, then router will prefer route with lowest administrative distance.       
  • Supports classless routing but RIPv2 also support VLSM’s
  • Subnet mask is included in route entry.
  • RIP use the Hop count for metric or choosing best path, path will less hop to a destination will be preferred in RIP.
  •  RIP is suitable for small network and it support only 15 hop count and a route at 16 hops will be unreachable and inaccessible.
  •  RIP send its routing updates every 30 seconds to multicast address
  •  RIP supports authentication
  • RIP carry 25 routes in its routing updates and if you use authentication then 24 routes per RIP message.
  • RIP Uses UDP port 520.
  • RIP provides different mechanism  for avoiding loops in networks, these methods are split horizon, poison reverse and

So if you have a small network then you can use the RIP, it’s easy to configure and easy to manage. RIPv2 also appears at the edge of larger inter-networks.