Solved: Re: EIGRP Neighbor Not On Common Subnet why? - Page 2

lowfell · ‎03-06-2019

I have two switches running EIGRP but get the following error messages

*Mar 6 16:06:19.511: %DUAL-6-NBRINFO: EIGRP-IPv4 100: Neighbor 172.18.8.1 (Vlan3) is blocked: not on common subnet (10.32.253.17/28)
*Mar 6 16:06:33.266: %DUAL-6-NBRINFO: EIGRP-IPv4 100: Neighbor 172.18.8.1 (Vlan3) is blocked: not on common subnet (10.32.253.17/28)
*Mar 6 16:06:47.191: %DUAL-6-NBRINFO: EIGRP-IPv4 100: Neighbor 172.18.4.1 (Vlan2) is blocked: not on common subnet (10.32.253.1/28)
*Mar 6 16:06:57.299: %DUAL-6-NBRINFO: EIGRP-IPv4 100: Neighbor 172.18.8.1 (Vlan3) is blocked: not on common subnet (10.32.253.17/28)
*Mar 6 16:07:10.092: %DUAL-6-NBRINFO: EIGRP-IPv4 100: Neighbor 172.18.4.1 (Vlan2) is blocked: not on common subnet (10.32.253.1/28)

Here is my config switch one.

FIRSTLY THE PORT CHANNEL

sw1#sho run int port-channel 1
Building configuration...

Current configuration : 171 bytes
!
interface Port-channel1
description *** Etherchannel FROM TenG3/0/1-4/0/1***
switchport trunk allowed vlan 2,3,267
switchport mode trunk

!

interface TenGigabitEthernet3/0/1
description *** MCR N5K Eth */* - ***
switchport trunk allowed vlan 2,3,267
switchport mode trunk
channel-group 1 mode on
!

!
interface TenGigabitEthernet4/0/1
description ***desc MCR N5K Eth */* - ***
switchport trunk allowed vlan 2,3,267
switchport mode trunk
channel-group 1 mode on
!!
interface Vlan2
description ***TEST_FCC_vlan2***
ip address 10.32.253.1 255.255.255.240
end

!

interface Vlan3
description ***TEST Voice Vlan FCC***
ip address 10.32.253.17 255.255.255.240

!

interface Vlan267
description ***New_Core_Routin_/30***
ip address 10.1.1.1 255.255.255.252
end

!

here is my EIGRP setup

router eigrp 100
network 10.1.1.0 0.0.0.3
network 10.32.253.0 0.0.0.15
network 10.32.253.16 0.0.0.15
!

#sho ip eigrp nei
EIGRP-IPv4 Neighbors for AS(100)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.1.1.2 Vl267 14 00:43:13 179 1074 0 1

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Now switch 2

!
interface Port-channel1
description ***LACP Etherchannel ***
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 2,3,267
switchport mode trunk
end

!
!
interface GigabitEthernet0/25
description *** UPLINK TRUNK to ***
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 2,3,267
switchport mode trunk
channel-group 1 mode on
!
interface GigabitEthernet0/26
description *** UPLINK TRUNK ***
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 2,3,267
switchport mode trunk
channel-group 1 mode on
!
!
!
interface Vlan2
description ***TEST_***
ip address 172.18.4.1 255.255.252.0
!
interface Vlan3
description ***TEST Vlan***
ip address 172.18.8.1 255.255.252.0
!

interface Vlan267
description *** Transit svi ***
ip address 10.1.1.2 255.255.255.252
!

!
!
router eigrp 100
network 10.1.1.0 0.0.0.3
network 172.18.4.0 0.0.3.255
network 172.18.8.0 0.0.3.255
no auto-summary
!
#sho ip eigrp nei
IP-EIGRP neighbors for process 100
H Address Interface Hold Uptime SRTT RTO Q Seq Type
(sec) (ms) Cnt Num
0 10.1.1.1 Vl267 15 00:52:36 1 4500 0 3

ON SWITCH TWO I GET OBVIOUSLY THE OPPOSITE MESSAGES. lIKE THIS

IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.17 not on common subnet for Vlan3
00:58:57: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.1 not on common subnet for Vlan2
00:59:10: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.17 not on common subnet for Vlan3
00:59:24: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.17 not on common subnet for Vlan3
00:59:38: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.1 not on common subnet for Vlan2
00:59:52: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.17 not on common subnet for Vlan3
01:00:02: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.1 not on common subnet for Vlan2
01:00:14: IP-EIGRP(Default-IP-Routing-Table:100): Neighbor 10.32.253.17 not on common subnet for Vlan3

so, i think what you will say is "they need to be on the same subnet" ?

1. Whilst my vlans might have the same vlan numbers their subnet their ip ranges are different so why should this make a difference ?

2. what do I need to do to make this work?

3. I suspect it's something to do with Layer2 & layer3 mixup ?

Richard Burts · ‎03-07-2019

The point of EIGRP is to advertise to the switches subnets that are found only on the other switch. If switch 1 has some subnet (perhaps 192.168.5.0) and that subnet is not also physically present on switch 2 then switch 2 has no way to route to the hosts in that subnet. Advertising that subnet using EIGRP provides routing information so that switch 2 would be able to forward packets to that subnet.

HTH

Rick

HTH

Rick

lowfell · ‎03-08-2019

Brilliant. I've got it now. Thank you very much.

Richard Burts · ‎03-08-2019

You are welcome. I am glad that our suggestions have been helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions that have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.

HTH

Rick

HTH

Rick