BGP Explained in detail || BGP Overview, Message Types, States || CCNA & CCNP

This video contains the discussion about the BGP Routing protocol.

BGP : Border Gateway Protocol

BGP is a Exterior Gateway Protocol that is used to share the route information between different Autonomous sytem.

Open standard
EGP
Designed for huge inter-network like Internet.
Updates are incremental and trigger
Path Vector Protocol
It is application layer protocol uses port 179 TCP
It sends update to the manually defined neighbor as unicast
Metrics - Attributes (Many)
AD - 20External and 200 IBGP
Loop prevention mechanism
Slowest routing protocol in the world

Message Types
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Open
used to initiate a BGP session between 2 routers.
includes :
BGP version
Sender AS number
Hold Time (Cisco default 180 seconds)
BGP identifier
optional parameter
If want to reject the BGP open, then Notification message will be sent.

Keepalive
I am still alive, lets keep this BGP session open.
it will be sent one-third the "hold time", cisco default every 60 seconds.

update
If any new route added and existing route deleted.
Path Attributes

notification

Terminate or rejects a BGP connection.
Can include error message (" BGP version not supported")

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BGP States:
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Idle
BGP process just started up or BGP error just occurred

Connect
Initiated TCP socket to neighbor
Active
Repeatedly attempting TCP handshake to connect to neighbor
Open sent
TCP socket established, sent open message
Open Confirm
Received reply open back
Established
We have received a keepalive or update and are exchanging the data