Tejas Jain

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? 224.0.0.10 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

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

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

What are types of OSPF packets? Hello Database Description (DBD) Link-State Requests (LSR) Link-State Updates (LSU) Link-State Acknowledgements (LSAck) What is OSPF finite state machine? What are the states in OSPF neighborship? DOWN - No OSPF packets have been received on the interface ATTEMPT - Applies only to non-broadcast multi-access networks (NBMA) where the neighbors must be configured manually using the "neighbor x.x.x.x" command INIT - Router has seen a Hello message from an OSPF router TWO-WAY - A Hello message has been sent to the neighbor and the neighbor has replied with its Hello message. In Broadcast networks, the DR/BDR election takes place after this state EXSTART - DR and BDR establish OSPF adjacencies with each of the routers in the network. Master / Slave election takes place at this stage. The Master sends its DBD (Database Descriptor) first EXCHANGE - Routing information may be exchanged via DBD, Link State Requests (LSR) and Link State Updates (LS

What is the protocol number of OSPF? 89 What is the multicast address of OSPF messages? 224.0.0.5 for OSPF All-routers multicast 224.0.0.6 for OSPF All-Designated routers multicast What are the OSPF hello packet timers? Hello packets are sent every 10 seconds with the Dead timer being 40 seconds Is it mandatory to have OSPF process ID the same on adjacent routers to form OSPF neighborship? No What is the impact of interface MTU mismatch on adjacent OSPF routers? MTU is not checked during the formation of neighbor adjacency. However, mismatched MTU values impede in the successful exchange of Database Description (DD) packets and thereby prevent the neighbors from reaching the "FULL" neighborship state. What are the types of OSPF LSAs? Type 1 - Router LSA Type 2 - Network LSA Type 3 - Summary LSA Type 4 - ASBR Summary LSA Type 5 - External LSA Type 6 - Multicast OSPF (MOSPF) LSA Type 7 - Not-So-Stubby-Area (NSSA)LSA Type 8 - External Attribute LSA for BGP Who generates Typ

Dynamic routing protocol Administrative distance - 120 Metric for best path selection - Hop count (Route with lowest hop count preferred) Maximum hop count allowed - 15 Route is considered unreachable for hop count - 16 RIP versions - RIP version 1, RIP version 2, RIP-NG RIP version 1 Classful routing protocol i.e. doesn't send subnet mask information in the update messages Sends periodic updates as broadcast Destination IP address for broadcast - 255.255.255.255 Doesn't support authentication of update messages RIP version 2 Classless routing protocol but does support classful Sends periodic updates as multicast Destination IP address for multicast - 224.0.0.9 Supports authentication of update messages RIP-NG Classless routing protocol (of course, this is IPv6 we are talking about) Sends periodic updates as multicast Destination IPv6 address for multicast - FF02::9

The AD values of the protocols are generally different across different vendors and care must be taken to take this fact into account in case of multi-vendor environments. Cisco Directly Connected Interface = 0 Static route = 1 EIGRP summary route = 5 External Border Gateway Protocol (eBGP) = 20 Enhanced Interior Gateway Routing Protocol (EIGRP) - Internal = 90 Open Shortest Path First (OSPF) = 110 Intermediate System to Intermediate System = 115 Routing Information Protocol (RIP) = 120 Enhanced Interior Gateway Routing Protocol (EIGRP) - External = 170 Internal Border Gateway Protocol (iBGP) = 200 Juniper Directly Connected Interface = 0 Static route = 5 Intermediate System to Intermediate System - Level-1 Internal = 15 Intermediate System to Intermediate System - Level-2 Internal = 18 Routing Information Protocol (RIP) = 100 Summary Route (Aggregate route) = 130 Open Shortest Path First (OSPF) = 150 Intermediate System to Intermediate System - Level-1 External = 160 Intermediate Syst