# EIGRP neighbors blocked using DMVPN dual tunnels?
**URL:** https://forum.networklessons.com/t/eigrp-neighbors-blocked-using-dmvpn-dual-tunnels/15290
**Category:** EIGRP
**Created:** [September 4, 2021, 12:21am UTC](https://forum.networklessons.com/t/eigrp-neighbors-blocked-using-dmvpn-dual-tunnels/15290 "2021-09-04T00:21:06Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@rvandyke85](https://forum.networklessons.com/u/rvandyke85)
#### Post date: [September 4, 2021, 12:21am UTC](https://forum.networklessons.com/t/eigrp-neighbors-blocked-using-dmvpn-dual-tunnels/15290/1 "2021-09-04T00:21:06Z")
My setup is like my work. I have 1 NHS router
I have tunnel5 50.50.10.0 /24 dmpvn peer addresses
I have tunnel6 50.50.100.0 /24 dmpvn peer addresses
If I shut either off the tunnels work fine seperate on their own, and establish eigrp neighbor ships
but If I have both tunnels up same time I get message:
```auto
*Sep 4 01:23:30.312: %DUAL-6-NBRINFO: EIGRP-IPv4 2010: Neighbor 50.50.10.1 (Tunnel6) is blocked: not on common subnet (50.50.100.2/24)
A-DR-R1#
*Sep 4 01:23:57.875: %DUAL-6-NBRINFO: EIGRP-IPv4 2010: Neighbor 50.50.10.1 (Tunnel6) is blocked: not on common subnet (50.50.100.3/24)
B-INET-R2
```
at my work I dont have this issue. why am i forming neighborship with wrong ip subnets?
I have 2 NHS servers routers
1 is for tunnel 5 50.50.10.1/24- -this is dmvpn subnet peer address
1 is for tunnel 6 50.50.100.1/24 -this is dmvpn subnet peer address
I get why conflict with eigrp neighbors not same subnet.but my work below has 2 different dmvpn subnets 10.166.43 and 10.166.143 different subnet and neighbors formed fine?
What am I doing wrong ? thank you.
I dont understand eigrp message. I get that neighbors have to be on same subnet.
but at my work (10.166.0.0/24) . we have dmvpn tunnels on routers like this
tunnel5 is 10.166.43.0/24-this is dmvpn subnet peer address
tunnel6 is 10.166.143.0/24-this is dmvpn subnet peer address
and no error messages at my work?
this is message I am getting.
```auto
*Sep 4 00:16:45.459: %DUAL-6-NBRINFO: EIGRP-IPv4 2010: Neighbor 50.50.10.1 (Tunnel6) is blocked: not on common subnet (50.50.100.3/24)
B-INET-R2#
```
Thanks
Robert
---
### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [September 6, 2021, 5:35am UTC](https://forum.networklessons.com/t/eigrp-neighbors-blocked-using-dmvpn-dual-tunnels/15290/2 "2021-09-06T05:35:34Z")
Hello Robert
I have a suspicion about what is happening, but without knowing more about your topology at home and your topology at work I can’t be sure. Let me share what I’m thinking and it may be able to help you…
It looks like you’re configuring DMVPN with a dual hub. The way in which you implement this will also **depend upon your underlying physical and layer 2 infrastructure**. If your infrastructure is a single layer 2 infrastructure, such as a single ISP connecting to both hubs, then you have a single cloud topology. If you have separate ISPs, or at least separate networks for each hub, then you would have a dual cloud topology.
The difference is that in a single cloud scenario, both hubs are on the same broadcast domain, while in the second case, each hub is in its own broadcast domain.
My suspicion is that at work, you have a dual cloud scenario while at home you are configuring a single cloud scenario. In this case, even if you have exactly the same configuration as the devices at work, you will encounter these EIGRP error messages, if the underlying network infrastructure is single cloud. This is because the interface of one hub will receive EIGRP multicast packets destined for a different subnet.
Take a look at the following two lessons which depect the two scenarios. These lessons use OSFP, but you can still understand the difference in their topologies, and the reasons behind the “not on common subnet” error.
> **[DMVPN Dual Hub Single Cloud](https://networklessons.com/cisco/ccie-enterprise-infrastructure/dmvpn-dual-hub-single-cloud)**
>
> This lesson explains the configuration of adding a secondary hub to your DMVPN network using a single cloud on Cisco IOS routers.
> **[DMVPN Dual Hub Dual Cloud](https://networklessons.com/cisco/ccie-enterprise-infrastructure/dmvpn-dual-hub-dual-cloud)**
>
> This lesson explains how to add redundancy to your DMVPN network by adding a second hub and second cloud network.
Take a look at these and reexamine your topology. If you have further questions, let us know!
I hope this has been helpful!
Laz
---
### Author:  [@rvandyke85](https://forum.networklessons.com/u/rvandyke85)
#### Post date: [September 6, 2021, 3:56pm UTC](https://forum.networklessons.com/t/eigrp-neighbors-blocked-using-dmvpn-dual-tunnels/15290/3 "2021-09-06T15:56:10Z")
thank you so much for your deep reply. wow I hope to know as much as you some day. hahah
thanks for the articles these are just what I need. I could not find them .but you found them for me
Thanks man!
Robert