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OSPF-ISIS-BGP
OSPF & ISIS Fundamentals & BGP Overview
| Question | Answer |
|---|---|
| OSPF routers elect one special router and a backup one known as? | Designated Router (DR) Designated Backup Router (DBR) |
| What two Link State Advertisements are limited to flooding within the originating area? | LSA 1 - Router LSA LSA 2 - Network LSA Both limited to flooding within the origination area. |
| What two LSA's can flood to external areas? | LSA 3 - Network Summary LSA --Sent by Area Border Router to single attached area LSA 4 - ASBR Summary LSA --Sent by Autonomous System Border Router. Advertises exit point of the areas to external areas. Only sent between other ASBRs. |
| What LSA injects prefixes originated from other routing protocols into the OSPF domain? | LSA 5 - External LSA --Originated by ASBR. Flooded to all areas and all internal routers. Advertise a destination external to the OSPF. |
| What is IP Prefix Redistribution? | Process of inserting routing information into a protocol from outside? |
| How do ISIS routers routing information? | LSPs = Link State PDUs |
| When do routers move from Neighbors to being Adjacent? | Once both LSDs (Link State Databases) are synchronized and identical then the routers become adjacent. |
| What special address is used by ISIS systems? Two general divisions? | NSAP - Network Service Access Protocol 1) IDP = Initial Domain Part 2) DSP = Domain Specific Part |
| 3 Parts of simplified NSAP Address? | Area ID - Identifies area that IS belongs to SysID = Identifies IS System itself NSEL = NSAP Selector = Similar to TCP/UDP Port # |
| What is BGP? | An inter-Autonomous System routing protocol |
| When is i-BGP applicable? | When BGP is used to connect other BGP routers within the same autonomous system. If BGP routers are in different systems, e-BGP is used. |