07-16-2010 07:01 AM - edited 03-06-2019 12:03 PM
Hi all
Can anyone please explain to me what this is and how it would happen, and what to do to rectify it. I believe it is when a router does not get a response from a query, if so what is the impact on the querying router etc ?
cheers
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07-16-2010 11:43 AM
Hi all
Can anyone please explain to me what this is and how it would happen, and what to do to rectify it. I believe it is when a router does not get a response from a query, if so what is the impact on the querying router etc ?
cheers
Hi,
If the successor path is lost & there is no feasible successor path is available, router sends out query messages on all EIGRP enable interfaces & tries to find out an alternative path to the network. It is active state for that route.Now Router is waiting for reply from its neighbors. If reply is missing for 3 min, dat means router didn't get any reply from neighbors, then it becomes stuck in active. In this case, router reset the neighbor relationship with
the router who didn't replied back the query messages sent by the router.
To solve this problem, two method is used -
a) Router summarization
b) EIGRP Stub.
To disbale the stuck in active timer, the following command is used -
Router(config-router)# timers active-time disable.
Hope to Help !!
Ganesh.H
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07-16-2010 07:13 AM
Hello,
A route is said to be in stuck-in-active state when it has lost its
successor and has set a query to all its neighbors (no feasible successor)
and is yet to get a response. This happens when you have a flat topology and
you have lot of routers on one end and few on the other end and the route in
question belongs to one of those few routers.
Hope this helps.
Regards,
NT
07-16-2010 07:22 AM
furthermore, you can limit the query either byusing router summarization or using stub router.
07-16-2010 07:40 AM
Hi,
for an exam, one of the neighbor is down and there is no feasible successor in the topology table,
the roter set a query to all its neighbors.
if the router is having the 5 neighbors it is going to send the multicast message to query it's all the neighbors to know the backup path.
and waiting for the replay from all it is neighbors. once the rotuer recived the replay from all it is neighbors (5) after that once with the updates
it is going to update the routing table.
if any one of the neighbors failed to replay for the query the router will send the unicast to that neighbor up to 16 times and waiting for the replay.
this is also going to take long time depends up on your topology.
think about if that 5 neighbors having each 3 neibhbors the and they to also quering there neighbors to know the feasible successor that will take a long time.
this process is called struck-in-active.
there are four main reasons a route becomes SIA:
The link is unidirectional, so the query can´t possibly be answered.
The queried router´s resources are unavailable, generally due to high CPU utilization.
The queried router´s memory is corrupt or otherwise unable to allow the router to answer the query.
The link between the two routers is of low quality, allowing just enough packets through to keep the neighbor relationship intact, but not good enough to allow the replies through.
To sum it up, routes generally become SIA when a neighbor either doesn´t answer a query, or either the query or reply took a wrong turn somewhere. I told you it wasn´t the easiest thing to troubleshoot!
Stubbed route and router summarizations is the solution for this.
Regards,
Thinakaraj.M
07-16-2010 11:43 AM
Hi all
Can anyone please explain to me what this is and how it would happen, and what to do to rectify it. I believe it is when a router does not get a response from a query, if so what is the impact on the querying router etc ?
cheers
Hi,
If the successor path is lost & there is no feasible successor path is available, router sends out query messages on all EIGRP enable interfaces & tries to find out an alternative path to the network. It is active state for that route.Now Router is waiting for reply from its neighbors. If reply is missing for 3 min, dat means router didn't get any reply from neighbors, then it becomes stuck in active. In this case, router reset the neighbor relationship with
the router who didn't replied back the query messages sent by the router.
To solve this problem, two method is used -
a) Router summarization
b) EIGRP Stub.
To disbale the stuck in active timer, the following command is used -
Router(config-router)# timers active-time disable.
Hope to Help !!
Ganesh.H
Remember to rate the helpful post
07-16-2010 01:19 PM
hi there
thanks for this,
one more question, how does route summarization alleviate this problem ?
cheers
07-17-2010 01:03 AM
hi there
thanks for this,
one more question, how does route summarization alleviate this problem ?
cheers
Hi,
Route summarization helps to limit queries, as does configuration of EIGRP stub routers.
* Summarization minimizes the size of routing tables which means less CPU and memory usage and less bandwidth to transmit.
* Summarization reduces the chance of networks becoming stuck-in-active, because it reduces the number of routers the see each query. Therefore the chances of a query encountering issues is reduced.
NOTE: A router extends the query about a network only if it has an exact match in the routing table.
While EIGRP does not have the stub area options that OSPF does, EIGRP does allow a router to be configured as stub. This is commonly done with a hub-and-spoke configuration where the spoke routers do not have the resources to keep a full routing table. Since the spoke's next hop will always be the hub, all the spoke really needs is a default route. For this reason, the only neighbor an EIGRP stub router can have is the hub router
Hope to Help !!
Ganesh.H
Remember to rate the helpful post
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