What is BGP?

[lruberintwari]

Hi all,

Can someone tell me what's BGP? and why to use it? and in which circunstance to use it instead of others routing protocols like Eigrp,Rip or Ospf? What is his strenght and weakness? Help me to see clear with BGP. Thanks in advance

[Collin Clark]

A quick search on Cisco shows 1000's of results. Here is one of them

http://www.cisco.com/en/US/partner/docs/internetworking/technology/handbook/bgp.html

[lruberintwari]

Hi

The link was rich of infos but i am still wondering why do we use only BGP

as a routing protocol on internet? I saw that BGP has many features but i

also know that other routing protocols like Eigrp can do the same (e.g like

chosing the best path, load balancing for failover and ...). Another point

does BGP can be run on a LAN and WAN without another routing protocols on a

side? I usually see the mix of BGP with another routing protocol. thanks for

your help.

On Wed, Nov 3, 2010 at 6:07 PM, Collin_Clark <

[Collin Clark]

On LANs you want a protocol that can coverge fast. LAN's are usually smaller in size and and IGP can handle up/down links and convergence well. On the internet with thousands of routers, an IGP would be constantly reconverging making it very unstable. BGP addresses these issues and can scale.

lruberintwari wrote:
Hi
The link was rich of infos but  i am still wondering why do we use only BGP
as a routing protocol on internet? I saw that BGP has many features but i
also know that other routing protocols like Eigrp can do the same (e.g like
chosing the best path, load balancing for failover and ...). Another point
does BGP can be run on a  LAN and WAN without another routing protocols on a
side? I usually see the mix of BGP with another routing protocol. thanks for
your help.
On Wed, Nov 3, 2010 at 6:07 PM, Collin_Clark <

[Rick Morris]

BGP = Border Gateway Protocol

BGP is a dynamic routing protocol that will aid with redundancy, failover, and load sharing.

As with EIGRP there are neighbors.

You can control your route announcements incoming and outgoing.

You can have multiple peering sessions, but only one BGP process defined by an AS.

Some possible uses would be multiple carriers terminating ckt's into one device.  This is referred to as multihomed.

You can use this for multiple ckts from the same carrier.  You can have routemaps used for different reasons based on your traffic patterns needed.  BGP can be in two flavors, iBGP and eBGP.  iBGP is internal, same AS applied to both sessions and eBGP is external different AS applied for sessions.

BGP is typically a core routing and these routes are then redistributed into EIGRP, which is more LAN routing.

There is more details and as indicated by a previous post there are a lot of links on the subject.