Henry's Points

The detailed EIGRP Stub Routing is introduced in here. I couldn’t describe this better than that.

However, I do have my thinking for this feature and will present in here.

EIGRP Stub routing is basic idea to slove EIGRP stuck in active problem. It’s easy to illustrate in hub-and-spoke network that hub connects to WAN and all spokes have to go pass through hub to the outside world. So, the hub router doesn’t need to send QUERY to all spoke when WAN network changed. To enable “eigrp stub” on EIGRP process, hub router will not send QUERY to spokes.

We can do a simple testing for this feature. As we can see from diagram, R2 is a distribution router as hub and R3 is a access router as a spoke. R1 will be some router outside.

R1 <——–VLAN432—————-> R2 (Hub)<—————VLAN450——————-> R3 (Spoke)

When eigrp stub disabled on R3, we can do “debug eigrp package query“. We can see that R2 send QUERY to both VLAN432 and VLAN450.

23:02:06: EIGRP: Received QUERY on Vlan432 nbr 10.2.106.81
23:02:06:   AS 10, Flags 0×0, Seq 21/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely0
23:02:06: EIGRP: Enqueueing QUERY on Vlan450 iidbQ un/rely 0/1 serno 33-48
23:02:06: EIGRP: Enqueueing QUERY on Vlan432 iidbQ un/rely 0/1 serno 33-48
23:02:06: EIGRP: Sending QUERY on Vlan450
23:02:06:   AS 10, Flags 0×0, Seq 33/0 idbQ 0/0 iidbQ un/rely 0/0 serno 33-48
23:02:06: EIGRP: Sending QUERY on Vlan432
23:02:06:   AS 10, Flags 0×0, Seq 34/0 idbQ 0/0 iidbQ un/rely 0/0 serno 33-48

When eigrp stub is enabled, we can see that R2 will NOT send QUERY to vlan450 anymore. But it still send QUERY to VLAN432.

23:03:07: EIGRP: Received QUERY on Vlan432 nbr 10.2.106.81
23:03:07:   AS 10, Flags 0×0, Seq 24/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely0
23:03:07: EIGRP: Enqueueing QUERY on Vlan450 iidbQ un/rely 0/1 serno 81-96
23:03:07: EIGRP: Enqueueing QUERY on Vlan432 iidbQ un/rely 0/1 serno 81-96
23:03:07: EIGRP: Sending QUERY on Vlan432
23:03:07:   AS 10, Flags 0×0, Seq 40/0 idbQ 0/0 iidbQ un/rely 0/0 serno 81-96
23:03:10: EIGRP: Received QUERY on Vlan450 nbr 192.168.50.92
23:03:10:   AS 10, Flags 0×0, Seq 20/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely0

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