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NHPR behaves unexpectedly

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mathias...@gmx.de

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Oct 10, 2008, 8:16:11 AM10/10/08
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I set up a DMVPN with NHRP between two networks connected to the UMTS
net (my spokes) and one connected via DSL (my hub).

Everything seems to be fine, but when I traceroute from one spoke to
the other, I find that they communicate via the hub, and not - as I
expect - directly with each other.

The "show ip nhrp" output tells me, that the spokes learned the other
spoke´s outside IP address so they ought to be able to connect
directly to each other without the hub in between.

I attach the "show ip nhrp" output from one of my spokes, the
"traceroute" output of the same spoke an my configurations.

I use eigrp for routing.

Maybe someone has an idea?

Thank´s a lot.
Mathias


Spoke Router:

RT_UMTS#sho ip nhrp
172.16.1.10/32 via 172.16.1.10, Tunnel0 created 00:25:04, never expire
Type: static, Flags:
NBMA address: 1.2.3.4
172.16.1.30/32 via 172.16.1.30, Tunnel0 created 00:08:13, expire
01:52:42
Type: dynamic, Flags: router implicit
NBMA address: 80.187.114.1
(Claimed NBMA address: 172.20.225.217)
(no-socket)
192.168.30.10/32, Tunnel0 created 00:00:06, expire 00:02:58
Type: incomplete, Flags: negative
Cache hits: 1

RT_UMTS#traceroute 192.168.30.10

Type escape sequence to abort.
Tracing the route to 192.168.30.10

1 172.16.1.10 228 msec 260 msec 228 msec
2 172.16.1.30 460 msec 468 msec 460 msec
3 192.168.30.10 468 msec 1200 msec 448 msec

Spoke Router:

interface FastEthernet0/0
ip address 192.168.20.1

interface Tunnel0
ip address 172.16.1.20 255.255.255.0
ip mtu 1400
ip nhrp authentication DMVPN_NW
ip nhrp map multicast dynamic
ip nhrp map 172.16.1.10 1.2.3.4
ip nhrp network-id 1
ip nhrp nhs 172.16.1.10
ip nhrp cache non-authoritative
ip nhrp shortcut
ip nhrp redirect
ip tcp adjust-mss 1360
delay 1000
cdp enable
tunnel source Cellular0/1/0
tunnel destination 1.2.3.4
tunnel key 10000
tunnel protection ipsec profile DMVPN-PROF

Hub Router:

interface Tunnel0
ip address 172.16.1.10 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp authentication DMVPN_NW
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp holdtime 360
ip nhrp cache non-authoritative
ip nhrp redirect
ip tcp adjust-mss 1360
no ip split-horizon eigrp 1
delay 1000
cdp enable
tunnel source Dialer1
tunnel mode gre multipoint
tunnel key 10000
tunnel protection ipsec profile DMVPN-PROF

Helmut

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Oct 10, 2008, 9:09:16 AM10/10/08
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Does "show ip route" show 172.16.1.30 as the gateway for
192.168.30.0/24? I think no.
So why should your traceroute go directly to 172.16.1.30?
Add the line "no ip next-hop-self eigrp 1" to the tunnel configuration
of your hub router. Reset the eigrp adjacency and look again into your
routing table.
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mathias...@gmx.de

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Oct 14, 2008, 9:14:58 AM10/14/08
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Thank you guys for your hints.

Helmut, I followed your suggestion ("Add the line "no ip next-hop-self


eigrp 1" to the tunnel configuration of your hub router. Reset the

eigrp adjacency and look again into your routing table."), but it did
not change the situation; I still have only the hub router as an eigrp
neighbor.

Matt, do you suggest to configure an additional tunnel interface for
the spoke-to-spoke communication, or do you want me to change my
existing Tunnel0 interface into a mGRE tunnel?

("for dynamic spoke-to-spoke connectivity, you need to configure a
multipoint GRE (mGRE) tunnel interface on the spokes (similar
configuration to the hub); this is a pt-pt spoke as there is a "tunnel
destination" command present.")

As I can either have a tunnel destination or a multipoint GRE tunnel,
how would find the spokes their hub then (if I change my T0
interface)?

Mathias

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Helmut

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Oct 15, 2008, 4:18:07 AM10/15/08
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Hi Mathias,

sorry I have not seen that your spoke tunnel is configured as point to
point. Please follow the instruction from Matt and it should work.

Regards
Helmut

mathias...@gmx.de

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Oct 15, 2008, 12:18:19 PM10/15/08
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Thank´s again, Helmut and Matt!

Matt, my problem is, that at the spokes, which are connected to the
UMTS network, I do not have static IP addresses - each time they are
switched off and on again, they have another address. I only have a
static address for my hub router which is connected to the ADSL
network (which is the 1.2.3.4 in my configuration).

It is not possible here in Germany to get a static IP address for
UMTS.

Sorry, I missed to give you that information.

So I cannot just add another "ip nhrp map" with the address of my
other spoke as your example suggests.

Do you see any chance to get this running with changing IP addresses
at the spokes?

Thank´s again
Mathias

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