Lectures 11-14 - BGP

BGP TCP port

Only protocol that uses TCP on port 179

iBGP

When BGP is running between routers in the same AS

eBGP

BGP is running between routers in different AS 

BGP Speaker

Router running BGP is a BGP speaker. BGP peers can be located within one or different AS.

Weight

Path with the highest weight is used to leave 

Local pref 

Higher preference value is preferred

Well-known Mandatory

AS_PATH, NEXT_HOP, ORIGIN 

Well-known Discretionary

 LOCAL_PREF, ATOMIC_AGGREGATE

Optional Transitive

AGGREGATOR, COMMUNITY

Optional NonTransitive

 MULTI-EXIT-DISC, ORIGINATOR_ID, Cluster List

BGP Path Attributes

WM,WD,OT,ONT

Loop Prevention Mechanism

There is AS-Path attribute which states that router will drop BGP advertisement when it sees it own AS number in AS path attribute

Loop Prevention Mechanism 

There is AS-Path attribute which states that router will drop BGP advertisement when it sees it own AS number in AS path attribute

Route-maps 

Used when redistributing routes into an OSPF, RIP, EIGRP or BGP routing process.

Regex (Regular Expressions)

Defines the AS-path filter

Single Homed

1 link per ISP, 1 ISP

Dual Homed

2+ links per ISP, 1 ISP

Single Multi-homed

1 link per ISP, 2+ ISPs

Dual multihomed

2+ links per ISP, 2+ ISPs