BGP - Understanding BGP Session Types and Behaviors
7 important questions on BGP - Understanding BGP Session Types and Behaviors
What are the Administrative Distances for the routes from the two BGP session types?
- An iBGP session route has an AD of 200
- An eBGP session route has an AD of 20
What is important to note about multiple iBGP routers in a single AS?
- There is a Full Mesh Requirement for iBGP within an AS.
- This is because Loop Detection using the AS_Path attribute doesn't work so NLRI's received from an iBGP peer can't be forwarded to another iBGP peer
- iBGP routers might need to set up multi-hop sessions.
In iBGP, why is it more preferable to use Loopback addresses to establish neighbor adjacencies?
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What are the 3 rules of Route Reflectors?
- If a Route Reflector (RR) receives an NLRI from a non-RR client, the RR advertises the NLRI only to an RR-Client.
- If a RR receives an NLRI from an RR client it advertises the NLRI to RR-clients and non-RR-clients.
- If a RR receives an NLRI from an eBGP peer, it advertises the route to RR-clients and non-RR-clients.
How is a Route Reflector configured?
On the Route Reflector the following command is used:
Neighbor ip-address Route-Reflector-Client
What is the RFC1966 BGP Route Reflector idea used for?
When configured the Route Reflector reflects a route learned to other iBGP peers. To which peers is based on it's 3 basic rules.
How are Routing Loops prevented when using BGP Route Reflectors?
- ORIGINATOR_ID - Optional non-transitive
First RR sets the value to the RID of the router that injects the route into the AS. - CLUSTER_LIST - Optional non-transitive
Attribute is appended by the Route Reflector with its cluster ID. By default, this is the BGP Identifier or RID.
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