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Showing posts with the label EIGRP

EIGRP K-values

The ultimate variables that decide whether a particular metric component should contribute towards EIGRP metric calculation or not are the EIGRP K-values. There are 5 in all, K1 to K5 with K1 (in conjunction with Bandwidth) and K3 (in conjunction with Delay) used primarily for EIGRP metric calculation. The K-values are not interface specific but router specific, meaning, the same set of K-values would be applicable to all the interfaces of a particular EIGRP router. Of course, changes can be done under "router eigrp ASN" command and not under interface. The command "show ip protocols" would display the current K-values. show ip protocols (EIGRP K-values) Let us now modify the K-values.. EIGRP metric weights The excerpt shows that the moment K values are modified, the EIGRP adjacency goes down due to the mismatch of K-values with the neighboring router. The changes are reflected again by using the command : show ip protocols

EIGRP Adjacency

When your neighbor's router is on fire, your internet is not at stake! Wish the same were true in the EIGRP universe as well (unless you have a well designed redundant network, which unfortunately is not very often the case!) EIGRP works if and only if your router establishes an 'amicable' EIGRP neighborship with the adjacent EIGRP router. Well, this is not an issue in most cases. Of importance, here, is how do you quantify the 'amicability' of the EIGRP adjacency. Let's inspect various fields in the "show ip eigrp neighbor" output show ip eigrp neighbor Autonomous System (AS) number - Here, visible as "Process 100" - EIGRP uses the concept of  autonomous systems . An autonomous system is simply a group of EIGRP-enabled routers that should become EIGRP neighbors and exchange routes. Address: IP address of the EIGRP neighbor Interface : Which interface is this EIGRP adjacency is formed upon Hold timer: Hold down timer is the number of secon

EIGRP Interview Questions - Part 2

What is Advertised Distance in EIGRP? The Advertised Distance (AD) is the distance from a given neighbor to the destination router. Advertised distance is also called Reported Distance What is Feasible Distance? The Feasible Distance (FD) is the distance from the current router to the destination router. What is a Successor route? The EIGRP learned and computed best route that is eligible to be entered into routing table. By default, this is the route with the lowest metric and which meets the feasibility condition. What is Feasible Successor? If there is an alternate route and if it meets the feasibility condition, then it can be considered as a feasible successor. Do you use subnet mask or a wildcard mask in EIGRP "network" router command? EIGRP "network" command, by default, uses a classful network to advertise the connected networks. In order to be more specific in advertising the particular subnet, a wildcard mask is used.

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