DMVPN Phase 3 EIGRP Routing

(Rene Molenaar) #1

This topic is to discuss the following lesson:

(William L) #2

Hello René.

Great basic DMVPN lab but i have a request:

A DMVPN lab with 2 ISP’s (Multihoming) and load balancing using EIGRP Add-Path Support. I have had a hard time understanding the concept of that.

(Rene Molenaar) #3

Hi William,

I just published two examples for this:

DMVPN dual hub single cloud
DMVPN dual hub dual cloud

I haven’t included EIGRP Add-Path Support (yet) but this might be useful.

Rene

(shashi p) #4

Hi Rene,

If I want to migrate DMVPN phase 2 to phase 3 with EIGRP configured … what are the 3 changes that need to be done ??

(Rene Molenaar) #5

Hi Shashi,

For a detailed answer you can take a look here:

DMVPN Phase 3

DMVPN Phase 3 EIGRP

The short answer is this:

Hub(config)#interface tunnel 0
Hub(config-if)#ip nhrp redirect 
Spoke(config)#interface Tunnel 0
(config-if)#ip nhrp shortcut

And you need to advertise a summary route on the hub towards your spoke routers that covers the networks behind your spoke routers.

(Stephen M) #6

I’m using the IOS image you said you were but for some reason when i try show ip route nhrp it doesn’t recognize “nhrp”

R2#sho ip route nhrp
Translating "nhrp"
                ^
% Invalid input detected at '^' marker.

Also my dmvpn table looks a bit different but still says two entries only displays one line for them

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incompletea
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer

Tunnel0, Type:Spoke, NHRP Peers:2,
 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2   192.168.123.3    172.16.123.3    UP    never D
     1   192.168.123.1    172.16.123.1    UP 03:26:19 S

Last my route table doesn’t show the “%” and “H” indicators next to the routes when I configure as you did in your video.

Here is my image:
ROM: 3700 Software (C3725-ADVENTERPRISEK9-M), Version 12.4(15)T7, RELEASE SOFTWARE (fc3)

(Rene Molenaar) #7

Hi Stephen,

The 3725 router is quite old and there are some differences in the commands for IOS 12.4 or 15.x. I did all my DMVPN examples on a recent IOS 15 router:

R1#show version 
Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(1)T, RELEASE SOFTWARE (fc1)

Rene

(Andrew P) #8

Stephen,
If you happen to be using GNS3, my image of choice for DMVPN is the following:
c7200-adventerprisek9-mz.152-4.M6

(Stephen M) #9

Thanks Andrew I was able to get it to work with the 7200 image

Rene- I could not located the 3725 image you are using, what is the filename of it? as I would like to have it as well for sake of consistency.

(Rene Molenaar) #10

Hi Stephen,

The 3725 image I used for most GNS3Vault labs is c3725-adventerprisek9-mz.124-15.T7.bin. Any of the other T versions should be fine.

Rene

(Hany T) #11

Hi Rene,

I am a little bit confused here. When you advertise a default route with EIGRP, normally the spokes already have a default route (static maybe) because they are connected to the internet. in this case the EIGRP default route will not show in the routing table as it has a higher AD. and at the same time we cannot remove the default static route as we need it for the internet and also to reach the Hub router. To me, advertising a EIGRP default route here does not make sense because it will not be used. i was wondering if we can see a real summarization example at the Hub where the spokes still can directly communicate. thanks

(Rene Molenaar) #12

Hi @hsawiris,

In my example(s), I could get away with a default route in EIGRP since my NBMA network was all directly connected, I didn’t need a default route there.

In a production network, you probably use a default route for Internet access so you can’t get rid of it. I used loopbacks with 2.2.2.2/32 and 3.3.3.3/32 so for summarization, that’s a terrible example.

2.0.0.0/7 would work though…

On a real network, you would probably use subnets that are easy to summarize. For example, something like this:

* Spoke1: 10.10.0.0/24
* Spoke2: 10.10.1.0/24
* Spoke3: 10.10.2.0/24
* Spoke4: 10.10.3.0/24

You could then advertise 10.10.0.0/22 on the hub router.

Hope this helps!

Rene

(Lordly M) #13

I configured ip nhrp redirect on the hub, and ip nhrp shortcut on the spokes, I am also using 15.2(4)M6 but ip nhrp redirect doesn’t work

traceroute 3.3.3.3 source loopback 0 still hits the hub first
Tracing the route to 3.3.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 172.16.123.1 28 msec 16 msec 24 msec
  2 172.16.123.3 40 msec 16 msec *

Please advise

1 Like
(Rene Molenaar) #14

Hmm with the exact same config as I used? what if you clear NHRP, enable some debugs? does it tell you anything?