Presentation on BGP protocol

1. Presentation
(Topic: Loop Prevention Mechanism in BGP)
Presented By
Arafat Ashrafi Talha
Student ID: BWU/MNC/22/006
Course Name: Routing Professional
Course Code: MNCS301
Department of Cyber Science & Technology

2. Introduction:
BGP (Border Gateway Protocol) is a path vector
routing protocol used to exchange routing
information between Autonomous Systems
(ASes). BGP does not maintain a complete
topology of the network, but instead relies on
the AS_PATH attribute to track the path that
a route has taken to reach it. This attribute
contains a list of all AS numbers that the route
has traversed.

3. WHAT IS LOOP PREVENTION?
Loop prevention in networking is a feature that
prevents loops from forming. Loops can cause
network instability, congestion, and performance
degradation

4. BGP loop prevention mechanisms:
 AS_PATH attribute
 Split horizon rule
cloud

5. AS_PATHAttribute:
The AS_PATH attribute is a mandatory attribute in BGP
updates. It contains a list of all AS numbers that the
route has traversed to reach the advertising router.
When a BGP router receives an update, it compares the
AS_PATH attribute of the update to its own AS number.
If the BGP router sees its own AS number in the
AS_PATH attribute, it discards the update. This
prevents loops from forming in the BGP network.

6. Split Horizon Rule:
The split horizon rule states that a BGP router
should not advertise a route to a neighbor from
which it learned the route. This prevents loops
from forming in the BGP network, even if the
AS_PATH attribute is not properly configured.

7. Loop Prevention in IBGP andEBGP:
The loop prevention mechanisms described above
apply to both IBGP (Interior BGP) and EBGP
(Exterior BGP). IBGP is used to exchange routing
information between routers within the same AS.
EBGP is used to exchange routing information
between routers in different ASes.

8. Loop Prevention in IBGP:
In IBGP, the split horizon rule is the primary
loop prevention mechanism. This is because all
IBGP peers have the same AS number, so the
AS_PATH attribute cannot be used to prevent
loops.

9. Loop Prevention in EBGP:
In EBGP, the AS_PATH attribute is the primary
loop prevention mechanism. This is because each
EBGP peer has a unique AS number, so the
AS_PATH attribute can be used to track the
path that a route has taken to reach the
advertising router.

10. Conclusion:
BGP loop prevention mechanisms are essential for
preventing routing loops from forming in the BGP
network. Without loop prevention, routing loops
can cause network congestion, outages, and other
problems.

11. THANK YOU