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EIGRP Query propagation and distribute lists

EIGRP Scenario:

R1==R2==R3==R4

R1 advertises networks 1.1.1.1 and 2.2.2.2. R2 has distribute list out allowing only 1.1.1.1. R1-R2 link goes down. What queries do R3 and R4 receive?

6 REPLIES 6
Highlighted
Cisco Employee

EIGRP Query propagation and distribute lists

Hi Christiano,

The query will be sent out from R2 to R3 and the routes will be removed when it sends the EIGRP packets to the neighbor.

Captured the debug packets from the gns:

:   AS 10, Flags 0x0, Seq 21/45 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0

*Mar  1 00:17:18.803: EIGRP: Enqueueing ACK on Serial0/1 nbr 192.168.0.2

*Mar  1 00:17:18.803:   Ack seq 21 iidbQ un/rely 0/0 peerQ un/rely 1/0

*Mar  1 00:17:18.807: EIGRP: Sending ACK on Serial0/1 nbr 192.168.0.2

*Mar  1 00:17:18.807:   AS 10, Flags 0x0, Seq 0/21 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0

*Mar  1 00:17:18.819: EIGRP: Enqueueing REPLY on Serial0/0 nbr 20.0.0.1 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 39-39

*Mar  1 00:17:18.823: EIGRP: Requeued unicast on Serial0/0

*Mar  1 00:17:18.827: EIGRP: Sending REPLY on Serial0/0 nbr 20.0.0.1

*Mar  1 00:17:18.827:   AS 10, Flags 0x0, Seq 47/28 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 39-39

*Mar  1 00:17:18.959: EIGRP: Received ACK on Serial0/0 nbr 20.0.0.1

*Mar  1 00:17:18.963:   AS 10, Flags 0x0, Seq 0/47 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

*Mar  1 00:17:20.287: EIGRP: Sending HELLO on Loopback0

*Mar  1 00:17:20.287:   AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0

*Mar  1 00:17:20.291: EIGRP: Received HELLO on Loopback0 nbr 3.3.3.3

*Mar  1 00:17:20.295:   AS 10, Flags 0x0, Seq 0/0 idbQ 0/0

*Mar  1 00:17:20.295: EIGRP: Packet from ourselves ignored

*Mar  1 00:17:20.663: EIGRP: Sending HELLO on Serial0/1

*Mar  1 00:17:20.663:   AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0

*Mar  1 00:17:21.551: EIGRP: Received HELLO on Serial0/1 nbr 192.168.0.2

HTH

Regards

Inayath

Highlighted
Cisco Employee

EIGRP Query propagation and distribute lists

Hi Christiano

  • Eigrp Query process is triggered when successor goes down and doesn’t have any feasible successor available.
  • In your case when the link between R1 & R2 goes off. Router R2 will generate the query irrespective of distribute list applied for any route because R2 router has that route (i.e 2.2.2.2) in its topology and routing table but once the link between R1-R2 goes down R2 will not have the feasible successor so generate the query towards R3.
  • Now R3 router will receive the query and reply back to R2 as R3 doesn’t have any information about the feasible successor for route 2.2.2.2. so R3 router will not generate any query to R4.

Thanks & Regards

Sandeep

Highlighted

EIGRP Query propagation and distribute lists

Thanks for the answers.

"""

EIGRP Scenario:

R1==R2==R3==R4

R1 advertises networks 1.1.1.1 and 2.2.2.2. R2 has distribute list out allowing only 1.1.1.1. R1-R2 link goes down. What queries do R3 and R4 receive?

""""

OK so R2 sends out a query for 2.2.2.2 to R3 and R3 replies it doesn't know and doesn't pass query to R4. How about for 1.1.1.1? Since R3 had 1.1.1.1 in its topology table does it push the 1.1.1.1 query to R4?

Highlighted
Cisco Employee

EIGRP Query propagation and distribute lists

Yes R3 router will send the query to the R4: See the snip below on R4 router

*Mar  1 00:05:08.603: EIGRP: Sending HELLO on Ethernet0/0

*Mar  1 00:05:08.603:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0

*Mar  1 00:05:09.843: EIGRP: Received QUERY on Ethernet0/0 nbr 34.0.0.3

*Mar  1 00:05:09.847:   AS 1, Flags 0x0, Seq 8/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0

*Mar  1 00:05:09.847: EIGRP: Enqueueing ACK on Ethernet0/0 nbr 34.0.0.3

*Mar  1 00:05:09.851:   Ack seq 8 iidbQ un/rely 0/0 peerQ un/rely 1/0

*Mar  1 00:05:09.855: EIGRP: Sending ACK on Ethernet0/0 nbr 34.0.0.3

*Mar  1 00:05:09.859:   AS 1, Flags 0x0, Seq 0/8 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/0

*Mar  1 00:05:09.867: EIGRP: Enqueueing REPLY on Ethernet0/0 nbr 34.0.0.3 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 5-5

*Mar  1 00:05:09.871: EIGRP: Requeued unicast on Ethernet0/0

R4#

*Mar  1 00:05:09.875: EIGRP: Sending REPLY on Ethernet0/0 nbr 34.0.0.3

*Mar  1 00:05:09.875:   AS 1, Flags 0x0, Seq 5/8 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 5-5

Highlighted

EIGRP Query propagation and distribute lists

Thanks guys.

Highlighted
Cisco Employee

EIGRP Query propagation and distribute lists

Hi Christiano,

We are happy to help you.

Please mark the post as the answer, and rating the post will help others who may have the same question as you in the future.

Thank you

Regards

Inayath

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

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