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Showing posts from November 16, 2019

EIGRP Interview Questions - Part 1

Something about EIGRP.. Enhanced Interior Gateway Routing protocol It is an enhanced distance vector routing protocol based on Diffused Update Algorithm (DUAL) to calculate shortest path. Classless routing protocol Support for VLSM, route-summarization Supports unequal cost load balancing, incremental updates What parameters should match for EIGRP formation? Primary address should be used for forming EIGRP neighborship Autonomous System number K-values In case a static neighborship is configured, it must be done on both the sides What is the multicast address of EIGRP? What are the packet types used by EIGRP? Hello Acknowledgement Update Query Reply What are the basic components of EIGRP? Diffused Update Algorithm - It is used for selecting the lowest cost loop-free path for a given destination Reliable Transport Protocol - RTP is used in EIGRP for detecting packet loss and to ensure ordered delivery of packets Protocol Independent Module - Support for IP, IPX, AppleTalk, IP

OSPF Interview Questions - Part 4

How would you speed up OSPF convergence? Configure lower hello and dead interval timers Configure ISPF - incremental SPF --> The principle of ISPF is to update the affected nodes only without rebuilding the whole tree, thereby, resulting in a faster convergence and saving CPU intensive activity of processing. Configure OSPF's SPF throttling - The SPF throttling feature makes it possible to configure SPF scheduling in millisecond intervals and to potentially delay SPF calculations during network instability. Command : "timers throttle spf [spf-start] [spf-hold] [spf-max-wait] How do you modify the cost of a default route propogated into an area? Use the command "default-information originate [always] [metric value] [metric-type value] [route-map name]" where: metric value = numerical cost metric-type value = Type 1 / Type 2 etc. route-map name = name of the route-map Command to create a stub area area xx stub Command to create a totally stub area area xx stub no

OSPF Interview Questions - Part 3

What are the tables maintained by OSPF? Neighbor Table : This table stores information about all the OSPF neighbors. Can be displayed using the command : show ip ospf neighbor Database / Topology Table : This table stores link state database of all the OSPF learned routes. Can be displayed using the command : show ip ospf database Routing table : After running the SPF algorithm on all the routes in the database table, the best route is selected and promoted to the Routing table. Can be displayed using the command : show ip route ospf What are the benefits of dividing an OSPF domain into multiple areas? Decrease routing overhead per router (this especially makes sense for internal non-backbone routers i.e. routers inside a single non-backbone area Ensure speedy convergence.. less routes implies faster processing Confine network instability into single area.. the inter-area summary routes and the routes from special areas such as stub, totally stub, NSSA, totally NSSA are usually &quo