Question about EIGRP SIA

e24ohm

Folks:
I have a simulation question, but I am unsure what it is asking for, or what it means.

"you notice a large number of EIGRP SIA messages" What are SIA messages and where would I view these messages?

captobvious

Stuck In Active Routes

miller811

Keep reading the material it is in there......

R3# show ip eigrp topology
IP-EIGRP Topology Table for AS(200)/ID(10.1.2.
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status

Passive is good in EIGRP
Active is bad.

When the router loses a route and has no feasible succesor, it attempt to find another route. It then sends an inquiry to all other non stub routers to determine if they have an alternate route to the destination. The problem is, it cannot proceed until every inquiry sent, is responded to, (whether it has a valid alternate route or not) every query must by answered. If any router fails to respond in three minutes, (default timer) the route goes into stuck in active SIA. The neighbor relationship is bounced on the router that did not not respond, and then the process continues, because the original router who intiated the inquiry now has to try to replace all of the routes on the router that was just bounced.

Cyclades

Hey Miller,

Nice explanation but I have doubt in this.

From the time any particular route goes down and there is no feasible successor the local router send a query and make the route active. If there is no reply from neighbor router with in 3 mins then that route goes to SIA correct?

And how long will it be in SIA before resetting the relation with that particular neighbor ?

miller811

If the router does not receive a reply to all the outstanding queries within 3 minutes (the default time), the route goes to the stuck-in-active (SIA) state. When a route goes to SIA state, the router resets the neighbor relationships for the neighbors that failed to reply. This causes the router to recompute all routes known through that neighbor and to re-advertise all the routes it knows about to that neighbor.

e24ohm

miller811 wrote: »

Keep reading the material it is in there......

R3# show ip eigrp topology
IP-EIGRP Topology Table for AS(200)/ID(10.1.2.
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status

Passive is good in EIGRP
Active is bad.

When the router loses a route and has no feasible succesor, it attempt to find another route. It then sends an inquiry to all other non stub routers to determine if they have an alternate route to the destination. The problem is, it cannot proceed until every inquiry sent, is responded to, (whether it has a valid alternate route or not) every query must by answered. If any router fails to respond in three minutes, (default timer) the route goes into stuck in active SIA. The neighbor relationship is bounced on the router that did not not respond, and then the process continues, because the original router who intiated the inquiry now has to try to replace all of the routes on the router that was just bounced.

Hey, thanks for so much detail. This really did help....cheers!!!

Cyclades

miller811 wrote: »

If the router does not receive a reply to all the outstanding queries within 3 minutes (the default time), the route goes to the stuck-in-active (SIA) state. When a route goes to SIA state, the router resets the neighbor relationships for the neighbors that failed to reply. This causes the router to recompute all routes known through that neighbor and to re-advertise all the routes it knows about to that neighbor.

Ya Miller I know that when a router SIA for a destination it resets the neighbor relationship but how long will it be in SIA before the neighbor reset ? Will reset happen immediately or for how long will it wait in SIA ?

miller811

Cyclades wrote: »

Ya Miller I know that when a router SIA for a destination it resets the neighbor relationship but how long will it be in SIA before the neighbor reset ? Will reset happen immediately or for how long will it wait in SIA ?

It is my understanding that the router is actively searching for a successor route for up to 3 minutes which is the default timer. If all queries are not responded to in the three minutes the route is then considered stuck in active, and the neighbor relationship is bounced at that time.

When a route goes active and queries are sent to neighbors, the route will remain active until a reply is received for every query. But what happens if a neighbor is dead or otherwise incapacitated and cannot reply? The route would stay permanently active. The active timer is designed to prevent this situation. The timer is set when a query is sent. If the timer expires before a reply to the query is received, the route is declared stuck-in-active, the neighbor is presumed dead, and it is flushed from the neighbor table. The SIA route and any other routes via that neighbor are eliminated from the route table. DUAL will be satisfied by considering the neighbor to have replied with an infinite metric.

Cyclades

So it immediately resets the neighbor relationship after coming to SIA, right ?

luke_bibby

It was my understanding that the neighbor relationship was not bounced if you have an IOS that supports Active Process Enhancement? - the Queried neighbor replies with an SIA-Reply packet after a minute and a half to the the requesting neighbor to inform it of the status in finding an alternate route

networker050184

Cyclades wrote: »

So it immediately resets the neighbor relationship after coming to SIA, right ?

Yes it will bounce the neighbor immediately except in the case luke_bibby described above. If the neighbor misses three SIA-Queries the neighbor is bounced.

Cyclades

networker050184 wrote: »

Yes it will bounce the neighbor immediately except in the case luke_bibby described above. If the neighbor misses three SIA-Queries the neighbor is bounced.

Thanks Luke and Networker You guys RoK! .