APPLICATION OF BGP

[sarahr202]

Hi everybody.

I was reading about  bgp  and igp( ospf,eigrp).    Based on  what I had  read could be summed as "It was sheer  number of routes that necessitated the use of bgp rather than  igp".

I am just thinking   what possible applications there might be where  we don't have tons of routes to be exchanged, but bgp can still be used.

Let say we have a customer named  abc inc,

Abc inc is connected to an ISP1  via two  links, link1 link2.

abc-----------link1- isp

     -----------link2  

In my scenario,  what conditions require the use of bgp?

thanks and have a good weekend

.

[Marwan ALshawi · Accepted solution]

Hi sarah,

BGP is also called path victor protocol, BGP diffrent from other routing protocols because it Handel routing and routing policies a bit difrent

BGP provide many inbound and outbound filtering and path selections capabilities by using BGP attributes such as AS path, local preference, Weight ( cisco Only ), routing origin, ..etc

and it is useful in the case yo motioned for easier, and better loadbalcing or redundancy of two links to two differnt ISPs

also it is good option becuase even if there are few routes but BGP fit very well between to routing domains such as the case above customer to ISP

or company A to company B where each side has its own routing/IGP and peer with other domain using bgp with controlled routing exchange

IGP is limited in this area because IGP lack to the attributes that BGP has such as the ones mentioned above and it can only uses limited metrecs and filtering capabilities which will  make it not the best options to be used but it is still an option could be used if must !

hope this help

[Craig_Baum_2 · Accepted solution]

BGP is an exterior gateway protocol. As such it's prime role was to exchange routing information between different administrative areas.

The idea being that a set of routes are only available within an autonomous system so a neighbouring system doesnt need to bother about if or when routes within the neighbours IGP changes only if they no longer become available..

BGP is thus slower to converge and doesn't need frequent updates making it easier to handle more routes.

Sent from Cisco Technical Support iPad App

[Kishore Chennupati · Accepted solution]

Hi Sarah,

I am just thinking   what possible applications there might be where  we don't have tons of routes to be exchanged, but bgp can still be used.

BGP is also used in IP VPN's as PE-CE protocol . In IP VPN's it can be used even for smaller set of routes. BGP can also be used within medium scale businesses when 2 seperate businesses need to talk to each other. you can simply use BGP to peer with AS's

The power of BGP is its ability to influence routing using heaps of BGP atributes like local-pref, med, as_path prepend etc...and so on

Let say we have a customer named  abc inc,
Abc inc is connected to an ISP1  via two  links, link1 link2.
abc-----------link1- isp
     -----------link2   
In my scenario,  what conditions require the use of bgp?

In your case, you can use BGP to have  primary /backup link scenario or you can use both links to load share even with small number of routes depending if you are multihomed to single ISP or Dual ISP's

HTH

Kishore