Cisconinja’s Blog

EIGRP SIA-Query and SIA-Reply

Posted by Andy on September 18, 2009

EIGRP SIA Query and Reply

R1:
interface Serial0/0
 ip address 10.0.12.1 255.255.255.0
 ip hold-time eigrp 1 500
 no keepalive
!
router eigrp 1
 network 10.0.0.0
 eigrp log-neighbor-changes

R2:
interface Loopback0
 ip address 10.2.2.2 255.255.255.0
!
interface Serial0/0
 ip address 10.0.12.2 255.255.255.0
 no keepalive
!
interface Serial0/1
 ip address 10.0.23.2 255.255.255.0
!
router eigrp 1
 timers active-time 1
 network 10.0.0.0
 eigrp log-neighbor-changes

R3:
interface Loopback0
 ip address 10.3.3.3 255.255.255.0
!
interface Serial0/0
 ip address 10.0.23.3 255.255.255.0
!
router eigrp 1
 timers active-time 1
 network 10.0.0.0
 eigrp log-neighbor-changes

This first example uses IOS version 12.0(5), which does not have support for SIA-query and SIA-reply messages.  The active timer has been lowered to 1 minute on R2 and R3 in order to see the results faster.  Keepalives have been disabled on the R1-R2 link and the hold timer increased on R1 to prevent R2 from discovering that R1 is down before the active timer expires.  We will shut down R1 S0/0 so that R1 stops receiving traffic from R2, and then shut down R3’s loopback:

R1:
interface Serial0/0
 shutdown

R3:
interface Loopback0
 shutdown

When R3’s loopback gets shutdown, R3 sends a query to R2 for 10.3.3.0/24.  R2 acknowledges the query and sends queries to both R1 and R3 for the route.  R3 acknowledges the query and sends a reply with it’s current metric (infinity).  R2 does not receive an ACK to the query that it sent to R1 so it continues to retransmit it.  R3 continues to wait on a reply from R2, but R2 can’t reply until it receives an ACK and a reply from R1:

1-R3-Topology-Table

1-R2-Topology-Table

R3#debug eigrp packets update ack query reply
Mar 1 00:14:26.075: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 serno 23-23
Mar 1 00:14:26.079: EIGRP: Enqueueing QUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 23-23
Mar 1 00:14:26.079: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.079: AS 1, Flags 0x0, Seq 21/28 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 23-23
Mar 1 00:14:26.159: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.159: AS 1, Flags 0x0, Seq 0/21 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:14:26.191: EIGRP: Received QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.191: AS 1, Flags 0x0, Seq 31/21 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:14:26.191: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.195: Ack seq 31 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:26.195: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.195: AS 1, Flags 0x0, Seq 0/31 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:26.207: EIGRP: Enqueueing REPLY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 24-24
Mar 1 00:14:26.211: EIGRP: Sending REPLY on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.211: AS 1, Flags 0x0, Seq 22/31 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 24-24
Mar 1 00:14:26.255: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:14:26.255: AS 1, Flags 0x0, Seq 0/22 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

 

R2#debug eigrp packets update ack query reply
Mar 1 00:14:26.823: EIGRP: Received QUERY on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.823: AS 1, Flags 0x0, Seq 21/28 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:14:26.823: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.827: Ack seq 21 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:26.827: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.827: AS 1, Flags 0x0, Seq 0/21 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:26.839: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 serno 18-18
Mar 1 00:14:26.839: EIGRP: Enqueueing QUERY on Serial0/1 iidbQ un/rely 0/1 serno 18-18
Mar 1 00:14:26.843: EIGRP: Enqueueing QUERY on Serial0/0 nbr 10.0.12.1 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 18-18
Mar 1 00:14:26.843: EIGRP: Enqueueing QUERY on Serial0/1 nbr 10.0.23.3 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 18-18
Mar 1 00:14:26.843: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1
Mar 1 00:14:26.847: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:26.847: EIGRP: Sending QUERY on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.847: AS 1, Flags 0x0, Seq 31/21 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:26.911: EIGRP: Received ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.911: AS 1, Flags 0x0, Seq 0/31 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:14:26.935: EIGRP: Received REPLY on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.935: AS 1, Flags 0x0, Seq 22/31 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:14:26.935: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.935: Ack seq 22 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:26.935: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:14:26.935: AS 1, Flags 0x0, Seq 0/22 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:14:31.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 1, RTO 5000
Mar 1 00:14:31.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:36.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 2, RTO 5000
Mar 1 00:14:36.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:41.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 3, RTO 5000
Mar 1 00:14:41.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:46.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 4, RTO 5000
Mar 1 00:14:46.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:51.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 5, RTO 5000
Mar 1 00:14:51.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:14:56.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 6, RTO 5000
Mar 1 00:14:56.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:01.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 7, RTO 5000
Mar 1 00:15:01.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:06.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 8, RTO 5000
Mar 1 00:15:06.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:11.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 9, RTO 5000
Mar 1 00:15:11.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:16.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 10, RTO 5000
Mar 1 00:15:16.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:21.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 11, RTO 5000
Mar 1 00:15:21.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:26.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 12, RTO 5000
Mar 1 00:15:26.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:31.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 13, RTO 5000
Mar 1 00:15:31.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:36.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 14, RTO 5000
Mar 1 00:15:36.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:41.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 15, RTO 5000
Mar 1 00:15:41.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:46.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 16, RTO 5000
Mar 1 00:15:46.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:51.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 17, RTO 5000
Mar 1 00:15:51.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:15:56.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 18, RTO 5000
Mar 1 00:15:56.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:16:01.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 19, RTO 5000
Mar 1 00:16:01.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:16:06.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 20, RTO 5000
Mar 1 00:16:06.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18

The active timer expires first on R3, and R3 assumes R2 is the cause of the problem and clears the adjacency.  A couple seconds later, the adjacency is reestablished and all updates must be resent between R2 and R3.  The active timer expires on R2 a few seconds later and R2 clears the adjacency with R1.  It no longer needs to send a reply to R3 since R3 already reset the adjacency between R2 and R3:

R3#debug eigrp packets update ack query reply
Mar 1 00:16:05.295: %DUAL-3-SIA: Route 10.3.3.0/24 stuck-in-active state in IP-EIGRP 1. Cleaning up
Mar 1 00:16:05.295: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.23.2 (Serial0/0) is down: stuck in active
Mar 1 00:16:07.659: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.23.2 (Serial0/0) is up: new adjacency
Mar 1 00:16:07.659: EIGRP: Enqueueing UPDATE on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 1-1
Mar 1 00:16:07.663: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 00:16:07.663: AS 1, Flags 0x1, Seq 23/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 1-1
Mar 1 00:16:09.051: EIGRP: Received UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 00:16:09.051: AS 1, Flags 0x1, Seq 32/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:16:09.067: EIGRP: Enqueueing UPDATE on Serial0/0 iidbQ un/rely 0/1 serno 25-26
Mar 1 00:16:09.071: EIGRP: Enqueueing UPDATE on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 25-26
Mar 1 00:16:09.663: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2, retry 1, RTO 3000
Mar 1 00:16:09.663: AS 1, Flags 0x1, Seq 23/32 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 1-1
Mar 1 00:16:09.707: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:16:09.707: AS 1, Flags 0x0, Seq 0/23 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2
Mar 1 00:16:09.711: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 00:16:09.711: AS 1, Flags 0x0, Seq 24/32 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 25-26
Mar 1 00:16:09.739: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:16:09.739: AS 1, Flags 0x0, Seq 0/24 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

 

R2#debug eigrp packets update ack query reply
Mar 1 00:16:08.363: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.23.3 (Serial0/1) is down: peer restarted
Mar 1 00:16:09.695: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.23.3 (Serial0/1) is up: new adjacency
Mar 1 00:16:09.695: EIGRP: Enqueueing UPDATE on Serial0/1 nbr 10.0.23.3 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 1-18
Mar 1 00:16:09.699: EIGRP: Sending UPDATE on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:09.699: AS 1, Flags 0x1, Seq 32/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 1-18
Mar 1 00:16:10.383: EIGRP: Received UPDATE on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.383: AS 1, Flags 0x1, Seq 23/32 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:16:10.383: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.387: Ack seq 23 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:16:10.387: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.387: AS 1, Flags 0x0, Seq 0/23 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:16:10.395: EIGRP: Received UPDATE on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.395: AS 1, Flags 0x0, Seq 24/32 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:16:10.395: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.399: Ack seq 24 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:16:10.399: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:16:10.399: AS 1, Flags 0x0, Seq 0/24 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:16:11.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 21, RTO 5000
Mar 1 00:16:11.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:16:16.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 22, RTO 5000
Mar 1 00:16:16.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:16:21.347: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 23, RTO 5000
Mar 1 00:16:21.347: AS 1, Flags 0x0, Seq 30/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 00:16:21.403: %DUAL-3-SIA: Route 10.3.3.0/24 stuck-in-active state in IP-EIGRP 1. Cleaning up
Mar 1 00:16:21.403: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.12.1 (Serial0/0) is down: stuck in active

Note: The active timer is not exact and seems to vary quite a bit from the actual configured time.  In my tests, it took as long as 1 minute over the configured active time for a route to be declared SIA, so the active time may end up expiring on R2 before R3.

The full exchange of non-hello EIGRP packets between R2 and R3 from the time 10.3.3.0/24 went down looks like this:

1-Wireshark

Resetting the adjacency between R2 and R3 obviously does not help the situation and wastes bandwidth and processing on both routers as the adjacency has to be reestablished and updates resent.  Let’s try the same scenario again on IOS version 12.4(15)T5, which supports SIA-query and SIA-reply messages:

R1:
interface Serial0/0
 shutdown

R3:
interface Loopback0
 shutdown

The first part of what happens is the same as before.  R3 sends a query to R2 for 10.3.3.0/24.  R2 acknowledges the query and sends queries to both R1 and R3 for the route.  R3 acknowledges the query and sends a reply with it’s current metric (infinity).  R2 does not receive an ACK to the query that it sent to R1 so it continues to retransmit it.  R3 continues to wait on a reply from R2, but R2 can’t reply until it receives an ACK and a reply from R1:

R3#debug eigrp packets update ack query reply siaquery siareply
Mar 1 00:06:33.299: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 serno 10-10
Mar 1 00:06:33.303: EIGRP: Enqueueing QUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 10-10
Mar 1 00:06:33.307: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.307: AS 1, Flags 0x0, Seq 9/7 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 10-10
Mar 1 00:06:33.531: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.531: AS 1, Flags 0x0, Seq 0/9 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:06:33.535: EIGRP: Received QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.535: AS 1, Flags 0x0, Seq 13/9 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:06:33.535: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.539: Ack seq 13 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:33.543: EIGRP: Sending ACK on Serial0/0 nbr
10.0.23.2
Mar 1 00:06:33.543: AS 1, Flags 0x0, Seq 0/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:33.551: EIGRP: Enqueueing REPLY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 11-11
Mar 1 00:06:33.559: EIGRP: Sending REPLY on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.559: AS 1, Flags 0x0, Seq 10/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 11-11
Mar 1 00:06:33.759: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:06:33.759: AS 1, Flags 0x0, Seq 0/10 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

 

R2#debug eigrp packets update ack query reply siaquery siareply
Mar 1 00:06:33.787: EIGRP: Received QUERY on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.787: AS 1, Flags 0x0, Seq 9/7 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:06:33.791: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.791: Ack seq 9 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:33.795: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.799: AS 1, Flags 0x0, Seq 0/9 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:33.803: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 serno 6-6
Mar 1 00:06:33.803: EIGRP: Enqueueing QUERY on Serial0/1 iidbQ un/rely 0/1 serno 6-6
Mar 1 00:06:33.807: EIGRP: Enqueueing QUERY on Serial0/0 nbr 10.0.12.1 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 6-6
Mar 1 00:06:33.807: EIGRP: Enqueueing QUERY on Serial0/1 nbr 10.0.23.3 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 6-6
Mar 1 00:06:33.811: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1
Mar 1 00:06:33.815: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:33.815: EIGRP: Sending QUERY on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.819: AS 1, Flags 0x0, Seq 13/9 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:33.887: EIGRP: Received ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.887: AS 1, Flags 0x0, Seq 0/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:06:33.979: EIGRP: Received REPLY on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.979: AS 1, Flags 0x0, Seq 10/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:06:33.979: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.979: Ack seq 10 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:33.983: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:06:33.983: AS 1, Flags 0x0, Seq 0/10 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:06:38.815: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 1, RTO 5000
Mar 1 00:06:38.819: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:43.819: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 2, RTO 5000
Mar 1 00:06:43.823: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:48.823: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 3, RTO 5000
Mar 1 00:06:48.827: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:53.827: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 4, RTO 5000
Mar 1 00:06:53.831: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:06:58.831: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 5, RTO 5000
Mar 1 00:06:58.835: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6
Mar 1 00:07:03.835: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 6, RTO 5000
Mar 1 00:07:03.839: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 6-6

After approximately half of the configured active timer, R2 and R3 both send an SIA-query to the neighbor that hasn’t replied yet.  (R2’s SIA-query never actually gets sent to R1 since RTP uses a window size of 1 packet and it is still waiting for an ACK to the original query).  R2 ACKs R3’s SIA-query and sends an SIA-reply.  R3 resets the active timer when it receives the SIA-reply.  Since R2 does not receive an SIA-reply from R1, it does not reset the active timer, and once the active timer expires it declares the route stuck in active and resets the adjacency with R1.  R2 is then able to finally reply to R3’s query, and the R2-R3 adjacency does not have to be reestablished:

R3#debug eigrp packets update ack query reply siaquery siareply
Mar 1 00:07:06.087: EIGRP: Enqueueing SIAQUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 12-12
Mar 1 00:07:06.095: EIGRP: Sending SIAQUERY on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:06.095: AS 1, Flags 0x0, Seq 11/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 12-12
Mar 1 00:07:06.131: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:06.131: AS 1, Flags 0x0, Seq 0/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:07:06.135: EIGRP: Received SIAREPLY on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:06.135: AS 1, Flags 0x0, Seq 15/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:07:06.135: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:06.139: Ack seq 15 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:07:06.139: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:06.143: AS 1, Flags 0x0, Seq 0/15 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:07:33.655: EIGRP: Received REPLY on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:33.659: AS 1, Flags 0x0, Seq 16/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:07:33.659: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:33.659: Ack seq 16 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:07:33.663: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 00:07:33.667: AS 1, Flags 0x0, Seq 0/16 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0

 

R2#debug eigrp packets update ack query reply siaquery siareply
Mar 1 00:07:03.847: EIGRP: Enqueueing SIAQUERY on Serial0/0 nbr 10.0.12.1 iidbQ un/rely 0/1 peerQ un/rely 0/1 serno 7-7
Mar 1 00:07:06.367: EIGRP: Received SIAQUERY on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:06.367: AS 1, Flags 0x0, Seq 11/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 00:07:06.371: EIGRP: Enqueueing ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:06.371: Ack seq 11 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:07:06.375: EIGRP: Sending ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:06.375: AS 1, Flags 0x0, Seq 0/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 00:07:06.387: EIGRP: Enqueueing SIAREPLY on Serial0/1 nbr 10.0.23.3 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 8-8
Mar 1 00:07:06.395: EIGRP: Sending SIAREPLY on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:06.395: AS 1, Flags 0x0, Seq 15/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 8-8
Mar 1 00:07:06.535: EIGRP: Received ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:06.539: AS 1, Flags 0x0, Seq 0/15 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 00:07:08.839: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 7, RTO 5000
Mar 1 00:07:08.843: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 6-6
Mar 1 00:07:13.843: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 8, RTO 5000
Mar 1 00:07:13.847: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 6-6
Mar 1 00:07:18.847: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 9, RTO 5000
Mar 1 00:07:18.851: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 6-6
Mar 1 00:07:23.851: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 10, RTO 5000
Mar 1 00:07:23.855: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 6-6
Mar 1 00:07:28.855: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.12.1, retry 11, RTO 5000
Mar 1 00:07:28.859: AS 1, Flags 0x0, Seq 12/3 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 6-6
Mar 1 00:07:33.859: %DUAL-3-SIA: Route 10.3.3.0/24 stuck-in-active state in IP-EIGRP(0) 1. Cleaning up
Mar 1 00:07:33.863: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.12.1 (Serial0/0) is down: stuck in active
Mar 1 00:07:33.875: EIGRP: Enqueueing REPLY on Serial0/1 nbr 10.0.23.3 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 9-9
Mar 1 00:07:33.887: EIGRP: Sending REPLY on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:33.891: AS 1, Flags 0x0, Seq 16/11 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 9-9
Mar 1 00:07:34.039: EIGRP: Received ACK on Serial0/1 nbr 10.0.23.3
Mar 1 00:07:34.043: AS 1, Flags 0x0, Seq 0/16 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

The full exchange of EIGRP packets between R2 and R3 from the time 10.3.3.0/24 went down excluding hellos looks like this:

2-Wireshark

The two packets that show up as ‘unknown’ in wireshark are the SIA-query (OpCode 10) and the SIA-reply (OpCode 11).  No updates needed to be resent.

EIGRP attempts to send up to 3 SIA-queries to a neighbor about an active route.  Each SIA-query is sent at an interval of 1/2 of the active timer, and each SIA-reply causes the active timer to be reset.  After 3, the router stops sending SIA-queries even if an SIA-reply has been successfully received for each one and allows the active timer to expire if the reply to the original query still hasn’t been received.  To demonstrate this, we will set the active time back to the default of 3 minutes on R2.

R2:
router eigrp 1
 timers active-time 3

R1:
interface Serial0/0
 shutdown

R3:
interface Loopback0
 shutdown

R3#debug eigrp packets update ack query reply siaquery siareply
Mar 1 01:56:43.315: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 serno 14-14
Mar 1 01:56:43.319: EIGRP: Enqueueing QUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/0 serno 14-14
Mar 1 01:56:43.323: EIGRP: Sending QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.323: AS 1, Flags 0x0, Seq 13/16 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 14-14
Mar 1 01:56:43.547: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.551: AS 1, Flags 0x0, Seq 0/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:56:43.551: EIGRP: Received QUERY on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.555: AS 1, Flags 0x0, Seq 22/13 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 01:56:43.555: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.555: Ack seq 22 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:56:43.559: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.563: AS 1, Flags 0x0, Seq 0/22 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:56:43.579: EIGRP: Enqueueing REPLY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 15-15
Mar 1 01:56:43.583: EIGRP: Sending REPLY on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.583: AS 1, Flags 0x0, Seq 14/22 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 15-15
Mar 1 01:56:43.735: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:56:43.739: AS 1, Flags 0x0, Seq 0/14 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:57:13.963: EIGRP: Enqueueing SIAQUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 16-16
Mar 1 01:57:13.971: EIGRP: Sending SIAQUERY on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:13.971: AS 1, Flags 0x0, Seq 15/22 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 16-16
Mar 1 01:57:14.099: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:14.103: AS 1, Flags 0x0, Seq 0/15 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:57:14.107: EIGRP: Received SIAREPLY on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:14.111: AS 1, Flags 0x0, Seq 23/15 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 01:57:14.111: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:14.111: Ack seq 23 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:57:14.115: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:14.119: AS 1, Flags 0x0, Seq 0/23 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:57:45.863: EIGRP: Enqueueing SIAQUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 17-17
Mar 1 01:57:45.871: EIGRP: Sending SIAQUERY on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:45.871: AS 1, Flags 0x0, Seq 16/23 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 17-17
Mar 1 01:57:45.979: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:45.979: AS 1, Flags 0x0, Seq 0/16 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:57:46.003: EIGRP: Received SIAREPLY on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:46.003: AS 1, Flags 0x0, Seq 24/16 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 01:57:46.003: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:46.007: Ack seq 24 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:57:46.011: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:57:46.011: AS 1, Flags 0x0, Seq 0/24 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:58:18.447: EIGRP: Enqueueing SIAQUERY on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 18-18
Mar 1 01:58:18.455: EIGRP: Sending SIAQUERY on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:18.455: AS 1, Flags 0x0, Seq 17/24 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 18-18
Mar 1 01:58:18.575: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:18.579: AS 1, Flags 0x0, Seq 0/17 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:58:18.583: EIGRP: Received SIAREPLY on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:18.587: AS 1, Flags 0x0, Seq 26/17 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
Mar 1 01:58:18.587: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:18.587: Ack seq 26 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:58:18.591: EIGRP: Sending ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:18.595: AS 1, Flags 0x0, Seq 0/26 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0
Mar 1 01:58:51.695: %DUAL-3-SIA: Route 10.3.3.0/24 stuck-in-active state in IP-EIGRP(0) 1. Cleaning up
Mar 1 01:58:51.699: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.23.2 (Serial0/0) is down: stuck in active
Mar 1 01:58:56.391: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.23.2 (Serial0/0) is up: new adjacency
Mar 1 01:58:56.391: EIGRP: Enqueueing UPDATE on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/1 peerQ un/rely 0/0
Mar 1 01:58:56.403: EIGRP: Received UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.403: AS 1, Flags 0x1, Seq 27/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:58:56.407: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.407: AS 1, Flags 0x1, Seq 18/27 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
Mar 1 01:58:56.411: EIGRP: Enqueueing UPDATE on Serial0/0 iidbQ un/rely 0/1 serno 7-7
Mar 1 01:58:56.415: EIGRP: Enqueueing UPDATE on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 7-7
Mar 1 01:58:56.523: EIGRP: Received UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.527: AS 1, Flags 0x8, Seq 28/18 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2
Mar 1 01:58:56.527: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.531: Ack seq 28 iidbQ un/rely 0/1 peerQ un/rely 1/1
Mar 1 01:58:56.535: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.539: AS 1, Flags 0x8, Seq 19/28 idbQ 0/0 iidbQ un/rely 0/1 peerQ un/rely 0/1 serno 7-7
Mar 1 01:58:56.695: EIGRP: Received UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.695: AS 1, Flags 0x8, Seq 29/19 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2
Mar 1 01:58:56.695: EIGRP: Enqueueing UPDATE on Serial0/0 iidbQ un/rely 0/1 serno 19-20
Mar 1 01:58:56.699: EIGRP: Enqueueing ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.699: Ack seq 29 iidbQ un/rely 0/1 peerQ un/rely 1/1
Mar 1 01:58:56.703: EIGRP: Sending UPDATE on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.707: AS 1, Flags 0x8, Seq 20/29 idbQ 0/0 iidbQ un/rely 0/1 peerQ un/rely 0/1 serno 7-7
Mar 1 01:58:56.711: EIGRP: Enqueueing UPDATE on Serial0/0 nbr 10.0.23.2 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 19-20
Mar 1 01:58:56.827: EIGRP: Received ACK on Serial0/0 nbr 10.0.23.2
Mar 1 01:58:56.831: AS 1, Flags 0x0, Seq 0/20 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2

The route remains active for a little over 2 minutes (twice the active time and four times the SIA retransmit interval).  When the original reply still hasn’t been received from R2 and the active time expires after 3 SIA-queries/replies, R3 resets the adjacency and updates are resent.

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