EIGRP neighbor states.

[sudhakara.py]

Hi 

I know in OSPF there are many states, DOWN, Attempt,INit, 2way, exstart, exchange, load, full,

what about eigrp , is there any states like that ?

I am looking to know that, is there any states EIGRP router goes through before it forms the neighbor relationship. if there are no states in Eigrp, then what would be the neighbor states on EIGRP router, while establishing neighbor relationship or while sending HELLO(to create neighbor relationship),UPDATE,ACK packets ?  

Thanks in advance.

[InayathUlla Sharieff]

EIGRP has Active and passive states:-

A destination in the topology table can be marked either as passive or active. A passive state is a state when the router has identified the successor(s) for the destination. The destination changes to active state when the current successor no longer satisfies thefeasibility condition and there are no feasible successors identified for that destination (i.e. no backup routes are available). The destination changes back from active to passive when the router received replies to all queries it has sent to its neighbors. Notice that if a successor stops satisfying the feasibility condition but there is at least one feasible successor available, the router will promote a feasible successor with the lowest total distance (the distance as reported by the feasible successor plus the cost of the link to this neighbor) to a new successor and the destination will remains in the passive state.

2-

EIGRP uses hello packets to form adjacency between each other. 

When they want to become neighbor the following sequence will occur:

Hello

Update

Query

Reply

Acknowledge.

Please check below link how the neighbors between the two routers will form in eigrp :--

https://networklessons.com/eigrp/detailed-look-of-eigrp-neighbor-adjacency/

HT

[Richard Burts]

It seems to me that this question is asking about whether there are various "states" that EIGRP routers go through as they establish adjacency. And the answer to that is that no there are not various states that the routers go through. As the article from networklessons shows there is a process that EIGRP routers go through (hello, update, ack) but no series of neighbor states.

The previous responses have discussed the state of entries in the EIGRP table (active or passive) but this is different from the state of the neighbor.

HTH

Rick

[sudhakara.py]

Hi Richard

Thank you very much.

I was looking to know that, is there any states EIGRP router goes through before it forms the neighbor relationship. You are saying there are no states, then what would be the neighbor states on EIGRP router, while establishing neighbor relationship or while sending HELLO(to create neighbor relationship),UPDATE,ACK packets ?  

Thanks in advance.

[Richard Burts]

Some routing protocols like OSPF do define a series of states that the router will be in as it forms its neighbor relationship. Other routing protocols like EIGRP do not define a series of states that the router will be in as it forms its neighbor relationship. Since EIGRP does not define states then the question of what state the router will be in while it forms its neighbor relationship does not have any valid answer.

HTH

Rick

[Simrid123]

Once established, EIGRP has two main states; active and passive.   

When a EIGRP connection is in the 'active' state it means the adjacency is not formed and it is currently calculating best paths etc.  There is such thing as stuck in active, whereby the router has no received the relevant responses in time.  More information can be found at this thread:

https://supportforums.cisco.com/discussion/12034081/what-does-eigrp-stuck-inactive-state-mean

The 'passive' state is what every engineer wants.  It means that DUAL has successfully done its job and the relevant adjacency's and calculations have been met.