EIGRP TABLES AND TERMINOLOGY
A Router running EIGRP maintains three tables-
1. Neighbor Table-
By sending hello message EIGRP and OSPF create neighbor relationship and keep their information in Neighbor Table. If you talk about RIP then it doesn't create neighbor relationship it just send a multicast message and receive multicast messages of others.
2.Topology Table-
OSPF contain all possible path in Topology Table but EIGRP contain only Successor and Feasible Successor in Topology Table.
3.Routing Table-
Like other routing protocol EIGRP also have Routing Table which contain best path.
In this topology I have 3 routers R0, R1 and R2 as you can see. R1 is connected to R0 with 100 Kb link and R0 is connected to R2 with 50 Kb link.I sitting om switch 0 with blink eye.:P
Now EIGRP will choose 100 Lb link as primary.And 50 Kb link as a Backup.
1.Feasible Distance (FD)-
How far router from you. Lets cost from S0 to R1 and R2 is same that is 500. But Cost from R1 to R0 and R2 to R0 will be different because they both are connected with different speed link.Let cost for R1- R0 link is 1000 so cost for R2-R0 will we 2000.
So FD for primary link is -500 + 1000 = 1500
And FD for second link is -1000 + 1000 = 2000
2.Advertise Distance (AD)-
How far router is from your neighbor.
So AD for primary and secondary is same - 1000
3.Successor - Primary link is called successor.
4.Feasible Successor - Backup link is called Feasible.
Note- "To be considered a Feasible Successor AD must be less then FD of successor.
Here AD is 1000 and FD of successor is 1500 so it'll become FS."
Note- " SO if EIGRP doesn't has FS in topology table and in case of link failure it send Query Message to it's neighbor. And if it's neighbor found that path from another neighbor or itself it'll reply with AD and if it doesn't found any path it'll reply with AD with infinity value (router will not choose this one)."
5.Active Router -
Router which actively looking for backup.(not a good thing.)
6.Passive Router -
Router have at least one FS and everything is fine.
A Router running EIGRP maintains three tables-
1. Neighbor Table-
By sending hello message EIGRP and OSPF create neighbor relationship and keep their information in Neighbor Table. If you talk about RIP then it doesn't create neighbor relationship it just send a multicast message and receive multicast messages of others.
2.Topology Table-
OSPF contain all possible path in Topology Table but EIGRP contain only Successor and Feasible Successor in Topology Table.
3.Routing Table-
Like other routing protocol EIGRP also have Routing Table which contain best path.
Terminology-
In this topology I have 3 routers R0, R1 and R2 as you can see. R1 is connected to R0 with 100 Kb link and R0 is connected to R2 with 50 Kb link.I sitting om switch 0 with blink eye.:P
Now EIGRP will choose 100 Lb link as primary.And 50 Kb link as a Backup.
1.Feasible Distance (FD)-
How far router from you. Lets cost from S0 to R1 and R2 is same that is 500. But Cost from R1 to R0 and R2 to R0 will be different because they both are connected with different speed link.Let cost for R1- R0 link is 1000 so cost for R2-R0 will we 2000.
So FD for primary link is -500 + 1000 = 1500
And FD for second link is -1000 + 1000 = 2000
2.Advertise Distance (AD)-
How far router is from your neighbor.
So AD for primary and secondary is same - 1000
3.Successor - Primary link is called successor.
4.Feasible Successor - Backup link is called Feasible.
Note- "To be considered a Feasible Successor AD must be less then FD of successor.
Here AD is 1000 and FD of successor is 1500 so it'll become FS."
Note- " SO if EIGRP doesn't has FS in topology table and in case of link failure it send Query Message to it's neighbor. And if it's neighbor found that path from another neighbor or itself it'll reply with AD and if it doesn't found any path it'll reply with AD with infinity value (router will not choose this one)."
5.Active Router -
Router which actively looking for backup.(not a good thing.)
6.Passive Router -
Router have at least one FS and everything is fine.
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