DMVPN over IPSec

In the previous posts, we discussed simple DMVPN phase 1 and DMVPN phase 2 where no mechanism for data protection is used. Usually, DMVPN tunnels are built over the internet and sending our data traffic over the internet without encryption won’t be a good idea.

Hence in this post we will discuss DMVPN IPSec and see how we can add IPsec encryption to the data, thus securing our data while it traverses the internet.

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DMVPN over IPSec

We will still use the same topology as the one we used in our earlier posts as below:

dmvpn ipsec

 

The configuration for simple DMVPN Phase is already up and running in this lab. For configuration details to bring up the simple DMVPN tunnels please refer to post for DMVPN phase 1. We were running EIGRP as the dynamic protocol for the route advertisement.

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As per the logs below we see our tunnels are up:

R2#sh dmvpn | be peer

# Ent –> Number of NHRP entries with same NBMA peer

NHS Status: E –> Expecting Replies, R –> Responding, W –> Waiting

UpDn Time –> Up or Down Time for a Tunnel

==========================================================================

Interface: Tunnel0, IPv4 NHRP Details

Type:Spoke, NHRP Peers:1,

# Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb

—– ————— ————— —– ——– —–

1 9.9.0.1            192.168.10.1    UP 00:00:46     S

 R3#sh dmvpn | be peer

# Ent –> Number of NHRP entries with same NBMA peer

NHS Status: E –> Expecting Replies, R –> Responding, W –> Waiting

UpDn Time –> Up or Down Time for a Tunnel

==========================================================================

Interface: Tunnel0, IPv4 NHRP Details

Type:Spoke, NHRP Peers:1,

# Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb

—– ————— ————— —– ——– —–

1 9.9.0.1            192.168.10.1    UP 00:00:56     S

R2#ping 3.3.3.3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 100/123/156 ms

Now we add the following configuration to enable the IPsec encryption over the tunnels on each router:

crypto isakmp policy 1

encr 3des

hash md5

authentication pre-share

group 2

lifetime 86400

!

crypto isakmp key cisco address 0.0.0.0 0.0.0.0

!

crypto ipsec transform-set abc esp-3des esp-md5-hmac

!

crypto ipsec profile gre_protection

set security-association lifetime seconds 86400

set transform-set abc

!

interface Tunnel 0

tunnel protection ipsec profile gre_protection

After you configure the above on each router we see IPsec tunnels up and running:

R2#sh crypto isakmp sa

IPv4 Crypto ISAKMP SA

dst             src             state          conn-id status

9.9.0.1         9.9.0.2         QM_IDLE           1001 ACTIVE

9.9.0.2         9.9.0.1         QM_IDLE           1002 ACTIVE

IPv6 Crypto ISAKMP SA

R2#sh crypto ipsec sa

interface: Tunnel0

Crypto map tag: Tunnel0-head-0, local addr 9.9.0.2

protected vrf: (none)

local  ident (addr/mask/prot/port): (9.9.0.2/255.255.255.255/47/0)

remote ident (addr/mask/prot/port): (9.9.0.1/255.255.255.255/47/0)

   current_peer 9.9.0.1 port 500

PERMIT, flags={origin_is_acl,}

#pkts encaps: 152, #pkts encrypt: 152, #pkts digest: 152

#pkts decaps: 153, #pkts decrypt: 153, #pkts verify: 153

#pkts compressed: 0, #pkts decompressed: 0

#pkts not compressed: 0, #pkts compr. failed: 0

#pkts not decompressed: 0, #pkts decompress failed: 0

#send errors 0, #recv errors 0

local crypto endpt.: 9.9.0.2, remote crypto endpt.: 9.9.0.1

path mtu 1500, ip mtu 1500, ip mtu idb FastEthernet0/0

current outbound spi: 0x58B95824(1488541732)

PFS (Y/N): N, DH group: none

Similarly on R3 we see the crypto tunnels:

R3#sh crypto isakmp sa

IPv4 Crypto ISAKMP SA

dst             src             state          conn-id status

9.9.0.1         9.9.0.3         QM_IDLE           1001 ACTIVE

9.9.0.3         9.9.0.1         QM_IDLE           1002 ACTIVE

IPv6 Crypto ISAKMP SA

R3#sh crypto ipsec sa

interface: Tunnel0

Crypto map tag: Tunnel0-head-0, local addr 9.9.0.3

protected vrf: (none)

local  ident (addr/mask/prot/port): (9.9.0.3/255.255.255.255/47/0)

remote ident (addr/mask/prot/port): (9.9.0.1/255.255.255.255/47/0)

   current_peer 9.9.0.1 port 500

PERMIT, flags={origin_is_acl,}

#pkts encaps: 160, #pkts encrypt: 160, #pkts digest: 160

#pkts decaps: 160, #pkts decrypt: 160, #pkts verify: 160

#pkts compressed: 0, #pkts decompressed: 0

#pkts not compressed: 0, #pkts compr. failed: 0

#pkts not decompressed: 0, #pkts decompress failed: 0

#send errors 0, #recv errors 0

 

local crypto endpt.: 9.9.0.3, remote crypto endpt.: 9.9.0.1

path mtu 1500, ip mtu 1500, ip mtu idb FastEthernet0/0

current outbound spi: 0x43B7E0B9(1136124089)

PFS (Y/N): N, DH group: none

inbound esp sas:

Now the traffic flows between R2 and R3 with IPsec encryption as seen in packet capture below:

dmvpn ipsec

Traffic capture without encapsulation:

dmvpn with ipsec

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