Lets start from first... I m gonna explain each attributes
one by one -
Well known attributes are must be recognized by
each compliant of BGP implementations. Well known attributes
are propagated to other neighbors also.
Optional attributes are recognized by some
implementation of BGP & expected that not recognized by
everyone. Optional attributes are propagated to their
neighbors based on the meanings.
Mandatory is BGP well known attributes. Mandatory
attributes are must be present in all update message passed
between BGP peers. It is present in route description.
Discretionary is BGP well known attributes.
Discretionary attributes are may be present on update message.
AS path is BGP well known mandatory attributes. AS
path defines the list of Autonomous System that a route has
passed through. AS path attributes are used in path
selection process & lowest path attributes will be preferred
over highest one.
Next hop is BGP well known mandatory attributes. In
BGP, next hop is the IP address which is used to reach the
advertising BGP router.
For EBGP, next hop is the ip address of the connection
between the peers.
For IBGP, EBGP next hop address is carried into local
Origin is BGP well known mandatory attributes.
Origion attributes define how BGP router learned about the
particular route. Origin attribute have three possible
values i.e. internal (i), External (e) & Incomplete (?).
BGP learned about the route from Interior
BGP learned about the router from External BGP.
The origin of the route is unknown or learned by
some other way. The origin of incomplete occurs when routes
are redistributed into BGP.
1. Due to lack of time, rest of attributes I'll discuss on
2. Its little bit difficult to draw diagram here & explain
each & every attributes.
3. If anyone need more about this, mail me on
Thanks & enjoys the weekend party tonight.... hehehe
What is the purpose and default value of the CDP timer command?
A.) 90 seconds; interval before an entry expires
B.) 60 seconds; interval between updates
C.) 60 seconds; interval before an entry expires
D.) 90 seconds; interval between updates