NRS2 - BGP
1. What was BGP originally designed for?: Exterior Routing Protocol - exchang- ing IP network reachability
2. Does BGP have a discovery mechanism?: No - its explicitly configures
3. What are message types?: Open, Keep Alice, Update, Notification
4. What are the connection states?: Connect (attempting outbound) Active (Awaiting inbound)
Open sent (awaiting open receive)
Open Confirm (Open received, awaiting KA) Established (KA received - ready)
5. What is the split horizon rule?: iBGP speakers cannot receive routes from iBGP peers
6. Must BGP peers be IP reachable?: Yes
7. Do iBGP peers have to be adjacent?: No - they can be, but not always
8. Do eBGP peers have to be adjacent?: Although typically adjacent, if multihop is configured to a higher TTL, they
dont have to be
9. What does RCV/ACT/SENT mean?: Indicates nmber of routes received, active and have been sent/.
10.What is NRLI?: Network Layer Reachability Info - an IP prefix and length
11.What is the purpose of path attributes?: Help determine preference given to NRLI advertised by BGP router
over other advertised routes
12.What are the types of path attributes?: Well known (mandatory or discre- tionary)
Optional (transitive and non-transitive)
13.What are the well known mandatory path attributes?: AS_PATH (list of AS that route update has visited)
NEXT_HOP (IP address of router that can receive and forward packets towards advertised prefix)
ORIGIN (Type of routing protocol that originally advertised prefix)
14.What are the well known discretionary path attributes?: LOCAL_PREFER- ENCE (degree of preference
assigned to route within local AS) ATOMIC_AGGREGATE (Whether AS_PATH info has been lost due to prefix aggre-
gation)
15.What are the optional transitive path attributes?: AS4_PATH (AS Path but with 4-Byte AS Number)
COMMUNITY (tag assigned to prefix indicating commonality with other routes with same prefix)
AGGREGATOR and AS4_AGGREGATOR (AS Number (2/4 byte) and ID of router that caused aggregated route)
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1. What was BGP originally designed for?: Exterior Routing Protocol - exchang- ing IP network reachability
2. Does BGP have a discovery mechanism?: No - its explicitly configures
3. What are message types?: Open, Keep Alice, Update, Notification
4. What are the connection states?: Connect (attempting outbound) Active (Awaiting inbound)
Open sent (awaiting open receive)
Open Confirm (Open received, awaiting KA) Established (KA received - ready)
5. What is the split horizon rule?: iBGP speakers cannot receive routes from iBGP peers
6. Must BGP peers be IP reachable?: Yes
7. Do iBGP peers have to be adjacent?: No - they can be, but not always
8. Do eBGP peers have to be adjacent?: Although typically adjacent, if multihop is configured to a higher TTL, they
dont have to be
9. What does RCV/ACT/SENT mean?: Indicates nmber of routes received, active and have been sent/.
10.What is NRLI?: Network Layer Reachability Info - an IP prefix and length
11.What is the purpose of path attributes?: Help determine preference given to NRLI advertised by BGP router
over other advertised routes
12.What are the types of path attributes?: Well known (mandatory or discre- tionary)
Optional (transitive and non-transitive)
13.What are the well known mandatory path attributes?: AS_PATH (list of AS that route update has visited)
NEXT_HOP (IP address of router that can receive and forward packets towards advertised prefix)
ORIGIN (Type of routing protocol that originally advertised prefix)
14.What are the well known discretionary path attributes?: LOCAL_PREFER- ENCE (degree of preference
assigned to route within local AS) ATOMIC_AGGREGATE (Whether AS_PATH info has been lost due to prefix aggre-
gation)
15.What are the optional transitive path attributes?: AS4_PATH (AS Path but with 4-Byte AS Number)
COMMUNITY (tag assigned to prefix indicating commonality with other routes with same prefix)
AGGREGATOR and AS4_AGGREGATOR (AS Number (2/4 byte) and ID of router that caused aggregated route)
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