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Configuring Site to Site VPN Connection via GRE Tunnels

Ismail Samah
Level 1
Level 1

I am trying to establish site-to-site VPN connection over the internet using GRE tunnels. I am able to reach from one WAN interface to the other. But I am not able to get the ISAKMP and IPSec to work. Please find below the configuration and a simplified network diagram below. In the below scenario I am also running BGP between these routers. The BGP neighbor-ships are formed via the tunnels. But I want the traffic between the tunnels to be encrypted. Since the IPsec and ISAKMP is not working the BGP routes and other traffic are not encrypted.

 

Therefore I would like to know what might the reason for this.

 

Config on VPN Router 1

crypto isakmp policy 1
 encr 3des
 authentication pre-share
 group 2
 lifetime 500
crypto isakmp key test_key1 address 192.168.30.1  
crypto isakmp key test_key1 address 192.168.30.2
crypto isakmp keepalive 60 20
crypto isakmp aggressive-mode disable
!
!
crypto ipsec transform-set high esp-3des esp-sha-hmac
 mode tunnel
!
!
!
crypto map CRYP_MAP_IPSEC 10 ipsec-isakmp
 set peer 192.168.20.1
 set security-association lifetime seconds 4000
 set transform-set high
 set pfs group2
 match address 110
crypto map CRYP_MAP_IPSEC 20 ipsec-isakmp
 set peer 192.168.20.2
 set security-association lifetime seconds 4000
 set transform-set high
 set pfs group2
 match address 111

!

interface Loopback0
 description IPsec_Tunnel0
 ip address 192.168.30.1 255.255.255.255
!
interface Loopback1
 description IPsec_Tunnel1
 ip address 192.168.30.2 255.255.255.255
!
interface Loopback2
 description BGP_Peer1
 ip address 192.168.40.1 255.255.255.255
!
interface Loopback3
 description BGP_Peer2
 ip address 192.168.40.2 255.255.255.255
!
interface Tunnel0
 ip unnumbered Loopback0
 tunnel source Loopback0
 tunnel destination 192.168.20.1
 crypto map CRYP_MAP_IPSEC
!
interface Tunnel1
 ip unnumbered Loopback1
 tunnel source Loopback1
 tunnel destination 192.168.20.2
 crypto map CRYP_MAP_IPSEC

!

interface gi0
 description #### CONNECTED TO Internet ####
 ip address 10.1.1.1 255.255.255.252
 ip access-group 100 in
 duplex auto
 speed auto

!

router bgp 64851
 bgp log-neighbor-changes
 neighbor BGP_PEER_1 peer-group
 neighbor BGP_PEER_1 remote-as 64859
 neighbor BGP_PEER_1 ebgp-multihop 255
 neighbor BGP_PEER_1 update-source Loopback2
 neighbor BGP_PEER_1 version 4
 neighbor BGP_PEER_1 next-hop-self
 neighbor BGP_PEER_2 peer-group
 neighbor BGP_PEER_2 remote-as 64859
 neighbor BGP_PEER_2 ebgp-multihop 255
 neighbor BGP_PEER_2 update-source Loopback3
 neighbor BGP_PEER_2 version 4
 neighbor BGP_PEER_2 next-hop-self
 neighbor 192.168.10.1 peer-group BGP_PEER_1
 neighbor 192.168.10.2 peer-group BGP_PEER_2

!

ip route 192.168.10.1 255.255.255.255 Tunnel0
ip route 192.168.10.2 255.255.255.255 Tunnel1
ip route 192.168.20.1 255.255.255.255 GigabitEthernet0
ip route 192.168.20.2 255.255.255.255 GigabitEthernet0
!
access-list 100 permit ip any any
access-list 110 permit gre host 192.168.30.1 host 192.168.20.1
access-list 110 permit gre host 192.168.20.1 host 192.168.30.1
access-list 111 permit gre host 192.168.30.2 host 192.168.20.2
access-list 111 permit gre host 192.168.20.2 host 192.168.30.2

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

Config on VPN Router 2

crypto isakmp policy 1
 encr 3des
 authentication pre-share
 group 2
 lifetime 500
crypto isakmp key test_key1 address 192.168.30.1  
crypto isakmp key test_key1 address 192.168.30.2
crypto isakmp keepalive 60 20
crypto isakmp aggressive-mode disable
!
!
crypto ipsec transform-set high esp-3des esp-sha-hmac
 mode tunnel
!
!
!
crypto map CRYP_MAP_IPSEC 10 ipsec-isakmp
 set peer 192.168.30.1
 set security-association lifetime seconds 4000
 set transform-set high
 set pfs group2
 match address 110
crypto map CRYP_MAP_IPSEC 20 ipsec-isakmp
 set peer 192.168.30.2
 set security-association lifetime seconds 4000
 set transform-set high
 set pfs group2
 match address 111

!

interface Loopback0
 description IPsec_Tunnel0
 ip address 192.168.20.1 255.255.255.255
!
interface Loopback1
 description IPsec_Tunnel1
 ip address 192.168.20.2 255.255.255.255
!
interface Loopback2
 description BGP_Peer1
 ip address 192.168.10.1 255.255.255.255
!
interface Loopback3
 description BGP_Peer2
 ip address 192.168.10.2 255.255.255.255
!
interface Tunnel0
 ip unnumbered Loopback0
 tunnel source Loopback0
 tunnel destination 192.168.30.1
 crypto map CRYP_MAP_IPSEC
!
interface Tunnel1
 ip unnumbered Loopback1
 tunnel source Loopback1
 tunnel destination 192.168.30.2
 crypto map CRYP_MAP_IPSEC

!

interface gi0
 description #### CONNECTED TO Internet ####
 ip address 10.1.1.2 255.255.255.252
 ip access-group 100 in
 duplex auto
 speed auto

!

router bgp 64859
 bgp log-neighbor-changes
 neighbor BGP_PEER_1 peer-group
 neighbor BGP_PEER_1 remote-as 64851
 neighbor BGP_PEER_1 ebgp-multihop 255
 neighbor BGP_PEER_1 update-source Loopback2
 neighbor BGP_PEER_1 version 4
 neighbor BGP_PEER_1 next-hop-self
 neighbor BGP_PEER_2 peer-group
 neighbor BGP_PEER_2 remote-as 64851
 neighbor BGP_PEER_2 ebgp-multihop 255
 neighbor BGP_PEER_2 update-source Loopback3
 neighbor BGP_PEER_2 version 4
 neighbor BGP_PEER_2 next-hop-self
 neighbor 192.168.40.1 peer-group BGP_PEER_1
 neighbor 192.168.40.2 peer-group BGP_PEER_2

!

ip route 192.168.40.1 255.255.255.255 Tunnel0
ip route 192.168.40.2 255.255.255.255 Tunnel1
ip route 192.168.30.1 255.255.255.255 gi0
ip route 192.168.30.2 255.255.255.255 gi0
!
access-list 100 permit ip any any
access-list 110 permit gre host 192.168.20.1 host 192.168.30.1
access-list 110 permit gre host 192.168.30.1 host 192.168.20.1
access-list 111 permit gre host 192.168.20.2 host 192.168.30.2
access-list 111 permit gre host 192.168.30.2 host 192.168.20.2

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

 

 

1 Accepted Solution

Accepted Solutions

Your Tunnel encryption configuration is incorrect...you need to do something the following at both ends.

crypto isakmp policy 10
encryption aes
hash sha
authentication pre-share
group 5
 
crypto isakmp key cisco address <PEER ADDRESS>
 
crypto ipsec transform-set MYSET esp-aes 256 esp-sha-hmac
 
crypto ipsec profile MYPROFILE
set transform-set MYSET
 
interface tunnel 10
ip unnumbered gig0/0
tunnel source gig0/0
tunnel destination <PEER ADDRESS>
tunnel mode ipsec ipv4
tunnel protection ipsec profile MYPROFILE
 

 

 

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View solution in original post

4 Replies 4

Your Tunnel encryption configuration is incorrect...you need to do something the following at both ends.

crypto isakmp policy 10
encryption aes
hash sha
authentication pre-share
group 5
 
crypto isakmp key cisco address <PEER ADDRESS>
 
crypto ipsec transform-set MYSET esp-aes 256 esp-sha-hmac
 
crypto ipsec profile MYPROFILE
set transform-set MYSET
 
interface tunnel 10
ip unnumbered gig0/0
tunnel source gig0/0
tunnel destination <PEER ADDRESS>
tunnel mode ipsec ipv4
tunnel protection ipsec profile MYPROFILE
 

 

 

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Dear MariusGunnerud,

Thanks for the advice. I will try out the new configuration and will let you know.

Dear MariusGunnerud,

I have managed to bring up the IPsec and ISAKMP to working status with same configuration.

Only I have included the following command that you recommended.

crypto ipsec profile MYPROFILE
set transform-set MYSET

and the following in the tunnel interface.

tunnel mode ipsec ipv4
tunnel protection ipsec profile MYPROFILE

Also I have included "crypto isakmp invalid-spi-recovery" as well.

Thank you very much for you help.

 

BR,

IsmailSamah

Glad you got it working! smiley

Thank you for the rating

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