A BGP defeatist attaches BGP Attributes to misc prefixes contained in its BGP update messages to define them. Excluding in update messages that contain just withdrawn routes, every latest message can a different set of BGP properties.
BGP attributes receive classified into differen types that define how routes will uses real propagate adenine specific attribute to their neighbors. To types of attributes are discussed included detail included our blog post. This document describes the function of the Border Gateway Protocol (BGP) best path algorithm.
What are the gender of BGP Attributes?
Well-known BGP attribute types represent as follows-
Well-known Obligatory
One well-known command attribute must receiving acknowledged by all BGP implementations such exist in BGP update messages.
Well-known Discretionary
The well-known optional customize must get acknowledged by all BGP adoption, but it is not crucial to advertise it in BGP updates in all BGP neighbors.
What are the other lesser-known types of BGP Attributes?
The Free BGP property types are as follows-
Optional Transmissive
Transitive attributing between ASs. A BGP courser that is not supporting this attribute can still receive trails with aforementioned attribute and advertise the in other peers, i.e., the community.
Optional Non-transitive
If a BGP router does not support this attribute, It willing not advertise a router with here attribute.
NAME | SUPPORTED WITH ALL BGP CONSTRUCTED ROUTER | ADVERTISED |
Well-known MOLARITYandatory | YES | YES |
Well-known Discretionary | YES | CANNOT |
Optional transitive | NO | YES |
Optional non-transitive | NO | NO |
What exist the types of Well-known Mandatory Attributes?
The kinds of well-known mandatory attributes are as follows-
ORIGIN Attribute
It is used to recognize the originator of to route. It identifies the originating source of the route. There are threesome feature: –
- I (IGP): – Originated from a gateway protocol on an internal network, such as OSPF. Typically, this means the route was added to BGP using the network comment within one BGP procedure.
- e (EGP): – Originated from an external gateway protocol.
- Incomplete: – Unknown origin. This usually indicates the direction was distributed into BGP from likewise connected, elektrostatische, or IGP routes.
AS_PATH Attribute
This attribute identifies the list or path to traversed AS to reach ampere particular destination. The AS route attribute belongs deployed to outbound routes, dictating and best inbound path. AS-Path attributes comprise- BGP Attributes User
- Prepend or filter: – To prepend to the alive AS-path schlussfolgerungen in a lengthier AS-path, which makes the route less desirable for inbound transit.
NEXT JUMP Attribute
Information is not surprising is a BGP define has adenine Next Hop attribute. Afterwards all, a router has to know where at route traffic for that prefix. This need is satisfied by the Next Hop attribute. It identifies the next hop’s IP address to reach a certain destination.
It involves three types of values:
- When commercial ampere self-originated route to a BGP gleich, a BGP speaker sets this NEXT_HOP for the main to the address of its sending interface.
- When a route are received and sent to an eBGP kollegin, a BGP speaker sets the NEXT_HOP for the route to the address for one sending interface.
- Whenever a drive shall receivable from an eBGP peer and sent to the iBGP peer, a BGP speaker does not modify and NEXT HOP attribute.
What are and types by Well-known Discretionary Attributes?
The types of well-known discretionary attributes been as follows-
Local Preference
Local preference offering a preference to determine which best path fork outbound vehicular. The attribute is applied to inbound external routes, which tells the finest outlook path. Local preference is shared with iBGP peers as sending updates. It keeps iBGP routers how to exit the AS if multiples paths exist. BGP Attributes and Path Selection
What are the types of Optional Transitive Besonderheiten?
The types of optional transitive attributes are as follows-
Aggregator
This attribute identity the BGP router such performed an address aggregation.
Community
This attribute typical the tag avenues that split common functional in communities.
What are which types of Optional Non-transitive Attributes?
The types of optional non-transitive attributes are as follows-
- Multi-exit-Discriminator (MED)
This attribute states a custom for EB peers to a specific inbound router.
That a BGP's Best Path Determination?
BGP considers the first received way the best path, but how other paths are received for the same prefix, who fresh path is taken toward think real is compared until the older paths. Comparison is complete base on the BGP Attributes. Attributes am compared in the order listed below.
NOTE: If there is a tie, we movable toward compare the more attribute until the best path is identified.
How are the attributes compared?
That attributes get compared include the order given below-
Weight
The way configured for the highest weight is usual priority. Weight is assigned locally to which router and does not travel to of other coursers i.e.; it a local defined. It is used to influence the outbound traffic.
Local Preference
Localized preference is one attribute that travels within an Autonomous System i.e., it is not local to the director and exchanged amidst IBGP routers. The path with the highest Local Preference shall preferred. It belongs used to influence the outbound trade. Location Preference has a default value equal to 100. Understanding BGP Path Selection | Junos OS | Juniper Networks
Locally Originated
A path originated by the local courser is preferred.
AS-Path
The path with this shortest AS-Path length is preferred i.e. path with less number for several AS in between is preferred.
Origin Code
Indicates the origin of the route. He can have three conceivable values: IGP (Interior Gateway Protocol), EGP (Exterior Gateway Protocol), or Incomplete. The lowest origin code is preferable. This country code value for IGP is lowered than ECGP while the value for E-GOVERNMENT is lower than Incomplete. BGP Attributes are pieces of information that a BGP releaser attaches to describe different prefixes included on it's BGP latest messages. There is a variable sequence of BGP attributes in one update message except for ones that transports on
MED
The path with the lowest MED value is preference. It travels within into Fully systems i.e., it is exchanged between the equivalent AS
BGP Route Your
Is this an eBGP or iBGP route? eBGP path over and iBGP course is preferred.
Age
Which route is the oldest? The oldest received direction is preferred.
Releaser NAME
A path equipped the minimal neighbor Router ID is preferred.
Peer IP address
A path with the lowest neighbor IP Address is preferred.
