Configuring Dynamic Multipoint VPN Using GRE Over IPsec With OSPF, NAT, and Cisco IOS Firewall
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Contents
Introduction
This document provides a sample configuration for Dynamic Multipoint VPN (DMVPN) using generic routing encapsulation (GRE) over IPsec with Open Shortest Path First (OSPF), Network Address Translation (NAT), and Cisco IOS® Firewall.
Prerequisites
Requirements
Before a multipoint GRE (mGRE) and IPsec tunnel can be established, you must define an Internet Key Exchange (IKE) policy by using the crypto isakmp policy command.
Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.
Components Used
The information in this document is based on these software and hardware versions:
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Cisco IOS® Software Release 12.2(15)T1 on the hub router and Cisco IOS Software Release 12.3(1.6) on the spoke routers
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Cisco 3620 as hub router, two Cisco 1720 routers and one Cisco 3620 router as spoke routers
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Conventions
Refer to the Cisco Technical Tips Conventions for more information on document conventions.
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.
Network Diagram
This document uses this network setup.
Configurations
This document uses these configurations.
| Hub - 3620-B |
|---|
W2N-6.16-3620-B#write terminal Building configuration... Current configuration : 2613 bytes ! version 12.2 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname W2N-6.16-3620-B ! logging queue-limit 100 ! memory-size iomem 10 ip subnet-zero ! ! ip cef no ip domain lookup ! !--- This is the Cisco IOS Firewall configuration and what to inspect. !--- This is applied outbound on the external interface. ip inspect name in2out rcmd ip inspect name in2out ftp ip inspect name in2out tftp ip inspect name in2out tcp timeout 43200 ip inspect name in2out http ip inspect name in2out udp ip audit po max-events 100 ! ! ! !--- Create an Internet Security Association and Key Management !--- Protocol (ISAKMP) policy for Phase 1 negotiations. crypto isakmp policy 5 authentication pre-share group 2 !--- Add dynamic pre-shared key. crypto isakmp key dmvpnkey address 0.0.0.0 0.0.0.0 crypto isakmp nat keepalive 20 ! ! !--- Create the Phase 2 policy for actual data encryption. crypto ipsec transform-set dmvpnset esp-3des esp-sha-hmac ! !--- Create an IPsec profile to be applied dynamically !--- to the GRE over IPsec tunnels. crypto ipsec profile dmvpnprof set transform-set dmvpnset ! ! ! ! ! ! ! ! ! ! ! no voice hpi capture buffer no voice hpi capture destination ! ! mta receive maximum-recipients 0 ! ! ! !--- This is the inbound interface. interface Loopback1 ip address 192.168.117.1 255.255.255.0 ip nat inside ! !--- Create a GRE tunnel template to be applied !--- to all the dynamically created GRE tunnels. interface Tunnel1 description MULTI-POINT GRE TUNNEL for BRANCHES bandwidth 1000 ip address 172.16.0.1 255.255.255.0 no ip redirects ip mtu 1416 ip nhrp authentication dmvpn ip nhrp map multicast dynamic ip nhrp network-id 99 ip nhrp holdtime 300 no ip route-cache ip ospf network broadcast no ip mroute-cache delay 1000 tunnel source FastEthernet0/0 tunnel mode gre multipoint tunnel key 100000 tunnel protection ipsec profile dmvpnprof ! !--- This is the outbound interface. interface FastEthernet0/0 ip address 14.24.117.1 255.255.0.0 ip nat outside ip access-group 100 in ip inspect in2out out no ip mroute-cache duplex auto speed auto ! interface Serial0/0 no ip address shutdown clockrate 2000000 no fair-queue ! interface FastEthernet0/1 no ip address no ip mroute-cache duplex auto speed auto ! !--- Enable a routing protocol to send/receive dynamic !--- updates about the private networks. router ospf 1 log-adjacency-changes network 172.16.0.0 0.0.0.255 area 0 network 192.168.117.0 0.0.0.255 area 0 ! !--- Except the private network traffic from the NAT process. ip nat inside source route-map nonat interface FastEthernet0/0 overload ip http server no ip http secure-server ip classless ip route 0.0.0.0 0.0.0.0 14.24.1.1 ip route 2.0.0.0 255.0.0.0 14.24.121.1 ! ! ! !--- Allow ISAKMP, ESP, and GRE traffic inbound. !--- Cisco IOS Firewall opens other inbound access as needed. access-list 100 permit udp any host 14.24.117.1 eq 500 access-list 100 premit esp any host 14.24.117.1 access-list 100 permit gre any host 14.24.117.1 access-list 100 deny ip any any !--- Except the private network traffic from the NAT process. access-list 110 deny ip 192.168.117.0 0.0.0.255 192.168.118.0 0.0.0.255 access-list 110 deny ip 192.168.117.0 0.0.0.255 192.168.116.0 0.0.0.255 access-list 110 deny ip 192.168.117.0 0.0.0.255 192.168.120.0 0.0.0.255 access-list 110 permit ip 192.168.117.0 0.0.0.255 any ! !--- Except the private network traffic from the NAT process. route-map nonat permit 10 match ip address 110 ! call rsvp-sync ! ! mgcp profile default ! dial-peer cor custom ! ! ! ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! ! end W2N-6.16-3620-B# |
| Spoke 1 - 3620-A |
|---|
W2N-6.16-3620-A#write terminal Building configuration... Current configuration : 2678 bytes ! version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname W2N-6.16-3620-A ! boot system flash slot0:c3620-ik9o3s7-mz.122-15.T1.bin logging queue-limit 100 ! memory-size iomem 15 ip subnet-zero ! ! ip cef no ip domain lookup ! !--- This is the Cisco IOS Firewall configuration and what to inspect. !--- This is applied outbound on the external interface. ip inspect name in2out rcmd ip inspect name in2out tftp ip inspect name in2out udp ip inspect name in2out tcp timeout 43200 ip inspect name in2out realaudio ip inspect name in2out vdolive ip inspect name in2out netshow ip audit po max-events 100 ! ! ! !--- Create an ISAKMP policy for !--- Phase 1 negotiations. crypto isakmp policy 5 authentication pre-share group 2 !--- Add dynamic pre-shared key. crypto isakmp key dmvpnkey address 0.0.0.0 0.0.0.0 ! ! !--- Create the Phase 2 policy for actual data encryption. crypto ipsec transform-set dmvpnset esp-3des esp-sha-hmac ! !--- Create an IPsec profile to be applied dynamically !--- to the GRE over IPsec tunnels. crypto ipsec profile dmvpnprof set transform-set dmvpnset ! ! ! ! ! ! ! ! ! ! ! no voice hpi capture buffer no voice hpi capture destination ! ! mta receive maximum-recipients 0 ! ! ! !--- This is the inbound interface. interface Loopback1 ip address 192.168.118.1 255.255.255.0 ip nat inside ! !--- Create a GRE tunnel template to be applied to !--- all the dynamically created GRE tunnels. interface Tunnel1 description HOST DYNAMIC TUNNEL bandwidth 1000 ip address 172.16.0.2 255.255.255.0 no ip redirects ip mtu 1416 ip nhrp authentication dmvpn ip nhrp map multicast dynamic ip nhrp map 172.16.0.1 14.24.117.1 ip nhrp map multicast 14.24.117.1 ip nhrp network-id 99 ip nhrp holdtime 300 ip nhrp nhs 172.16.0.1 no ip route-cache ip ospf network broadcast no ip mroute-cache delay 1000 tunnel source Ethernet0/0 tunnel mode gre multipoint tunnel key 100000 tunnel protection ipsec profile dmvpnprof ! !--- This is the outbound interface. interface Ethernet0/0 ip address 14.24.118.1 255.255.0.0 ip nat outside ip access-group 100 in ip inspect in2out out no ip mroute-cache half-duplex ! interface Ethernet0/1 no ip address half-duplex ! interface Ethernet0/2 no ip address shutdown half-duplex ! interface Ethernet0/3 no ip address shutdown half-duplex ! !--- Enable a routing protocol to send/receive dynamic !--- updates about the private networks. router ospf 1 log-adjacency-changes redistribute connected network 172.16.0.0 0.0.0.255 area 0 network 192.168.118.0 0.0.0.255 area 0 ! !--- Except the private network traffic from the NAT process. ip nat inside source route-map nonat interface Ethernet0/0 overload ip http server no ip http secure-server ip classless ip route 0.0.0.0 0.0.0.0 14.24.1.1 ip route 2.0.0.0 255.0.0.0 14.24.121.1 ! ! ! !--- Allow ISAKMP, ESP, and GRE traffic inbound. !--- Cisco IOS Firewall opens inbound access as needed. access-list 100 permit udp any host 14.24.118.1 eq 500 access-list 100 premit esp any host 14.24.118.1 access-list 100 permit gre any host 14.24.118.1 access-list 100 deny ip any any !--- Except the private network traffic from the NAT process. access-list 110 deny ip 192.168.118.0 0.0.0.255 192.168.117.0 0.0.0.255 access-list 110 deny ip 192.168.118.0 0.0.0.255 192.168.116.0 0.0.0.255 access-list 110 deny ip 192.168.118.0 0.0.0.255 192.168.120.0 0.0.0.255 access-list 110 permit ip 192.168.118.0 0.0.0.255 any ! !--- Except the private network traffic from the NAT process. route-map nonat permit 10 match ip address 110 ! call rsvp-sync ! ! mgcp profile default ! dial-peer cor custom ! ! ! ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! ! end W2N-6.16-3620-A# |
| Spoke 2 - 1720-b |
|---|
1720-b#write terminal Building configuration... Current configuration : 2623 bytes ! version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname 1720-b ! logging queue-limit 100 enable password cisco ! username 7206-B password 0 cisco ip subnet-zero ! ! no ip domain lookup ! ip cef !--- This is the Cisco IOS Firewall configuration and what to inspect. !--- This is applied outbound on the external interface. ip inspect name in2out rcmd ip inspect name in2out tftp ip inspect name in2out udp ip inspect name in2out tcp timeout 43200 ip inspect name in2out realaudio ip inspect name in2out vdolive ip inspect name in2out netshow ip audit po max-events 100 vpdn-group 1 request-dialin protocol pppoe ! ! ! ! ! !--- Create an ISAKMP policy for !--- Phase 1 negotiations. crypto isakmp policy 5 authentication pre-share group 2 !--- Add dynamic pre-shared key. crypto isakmp key dmvpnkey address 0.0.0.0 0.0.0.0 ! ! !--- Create the Phase 2 policy for actual data encryption. crypto ipsec transform-set dmvpnset esp-3des esp-sha-hmac ! !--- Create an IPsec profile to be applied dynamically !--- to the GRE over IPsec tunnels. crypto ipsec profile dmvpnprof set transform-set dmvpnset ! ! ! ! ! !--- This is the inbound interface. interface Loopback1 ip address 192.168.116.1 255.255.255.0 ip nat inside ! !--- Create a GRE tunnel template to be applied to !--- all the dynamically created GRE tunnels. interface Tunnel1 description HOST DYNAMIC TUNNEL bandwidth 1000 ip address 172.16.0.3 255.255.255.0 no ip redirects ip mtu 1416 ip nhrp authentication dmvpn ip nhrp map multicast dynamic ip nhrp map 172.16.0.1 14.24.117.1 ip nhrp map multicast 14.24.117.1 ip nhrp network-id 99 ip nhrp holdtime 300 ip nhrp nhs 172.16.0.1 no ip route-cache ip ospf network broadcast no ip mroute-cache delay 1000 tunnel source Dialer1 tunnel mode gre multipoint tunnel key 100000 tunnel protection ipsec profile dmvpnprof ! interface Ethernet0 no ip address half-duplex ! interface FastEthernet0 no ip address no ip mroute-cache speed auto pppoe enable pppoe-client dial-pool-number 1 ! !--- This is the outbound interface. interface Dialer1 ip address 2.2.2.10 255.255.255.0 ip inspect in2out out ip access-group 100 in encapsulation ppp dialer pool 1 dialer-group 1 ppp authentication pap chap callin ! !--- Enable a routing protocol to send/receive dynamic !--- updates about the private networks. router ospf 1 log-adjacency-changes redistribute connected network 172.16.0.0 0.0.0.255 area 0 network 192.168.116.0 0.0.0.255 area 0 ! !--- Except the private network traffic from the NAT process. ip nat inside source route-map nonat interface Dialer1 overload ip classless ip route 0.0.0.0 0.0.0.0 14.24.1.1 ip route 0.0.0.0 0.0.0.0 Dialer1 no ip http server no ip http secure-server ! ! ! !--- Allow ISAKMP, ESP, and GRE traffic inbound. !--- Cisco IOS Firewall opens inbound access as needed. access-list 100 permit udp any host 14.24.116.1 eq 500 access-list 100 premit esp any host 14.24.116.1 access-list 100 permit gre any host 14.24.116.1 access-list 100 deny ip any any !--- Except the private network traffic from the NAT process. access-list 110 deny ip 192.168.116.0 0.0.0.255 192.168.117.0 0.0.0.255 access-list 110 deny ip 192.168.116.0 0.0.0.255 192.168.118.0 0.0.0.255 access-list 110 deny ip 192.168.116.0 0.0.0.255 192.168.120.0 0.0.0.255 access-list 110 permit ip 192.168.116.0 0.0.0.255 any dialer-list 1 protocol ip permit ! !--- Except the private network traffic from the NAT process. route-map nonat permit 10 match ip address 110 ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! no scheduler allocate end 1720-b# |
| Spoke 3 - 1720-A |
|---|
W2N-6.16-1720-A#write terminal Building configuration... Current configuration : 2303 bytes ! version 12.2 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname W2N-6.16-1720-A ! logging queue-limit 100 ! memory-size iomem 25 ip subnet-zero ! ! no ip domain lookup ! ip cef !--- This is the Cisco IOS Firewall configuration and what to inspect. !--- This is applied outbound on the external interface. ip inspect name in2out rcmd ip inspect name in2out tftp ip inspect name in2out udp ip inspect name in2out tcp timeout 43200 ip inspect name in2out realaudio ip inspect name in2out vdolive ip inspect name in2out netshow ip audit notify log ip audit po max-events 100 ! ! ! ! !--- Create an ISAKMP policy for !--- Phase 1 negotiations. crypto isakmp policy 5 authentication pre-share group 2 !--- Add dynamic pre-shared key. crypto isakmp key dmvpnkey address 0.0.0.0 0.0.0.0 ! ! !--- Create the Phase 2 policy for actual data encryption. crypto ipsec transform-set dmvpnset esp-3des esp-sha-hmac ! !--- Create an IPsec profile to be applied dynamically !--- to the GRE over IPsec tunnels. crypto ipsec profile dmvpnprof set transform-set dmvpnset ! ! ! ! ! !--- This is the inbound interface. interface Loopback1 ip address 192.168.120.1 255.255.255.0 ip nat inside ! !--- Create a GRE tunnel template to be applied to !--- all the dynamically created GRE tunnels. interface Tunnel1 description HOST DYNAMIC TUNNEL bandwidth 1000 ip address 172.16.0.4 255.255.255.0 no ip redirects ip mtu 1416 ip nhrp authentication dmvpn ip nhrp map multicast dynamic ip nhrp map 172.16.0.1 14.24.117.1 ip nhrp map multicast 14.24.117.1 ip nhrp network-id 99 ip nhrp holdtime 300 ip nhrp nhs 172.16.0.1 ip ospf network broadcast no ip mroute-cache delay 1000 tunnel source FastEthernet0 tunnel mode gre multipoint tunnel key 100000 tunnel protection ipsec profile dmvpnprof ! interface Ethernet0 no ip address no ip mroute-cache half-duplex ! !--- This is the outbound interface. interface FastEthernet0 ip address 14.24.120.1 255.255.0.0 ip nat outside ip inspect in2out out ip access-group 100 in no ip mroute-cache speed auto ! !--- Enable a routing protocol to send/receive dynamic !--- updates about the private networks. router ospf 1 log-adjacency-changes redistribute connected network 172.16.0.0 0.0.0.255 area 0 network 192.168.120.0 0.0.0.255 area 0 ! !--- Except the private network traffic from the NAT process. ip nat inside source route-map nonat interface FastEthernet0 overload ip classless ip route 0.0.0.0 0.0.0.0 14.24.1.1 ip route 2.0.0.0 255.0.0.0 14.24.121.1 no ip http server no ip http secure-server ! ! ! !--- Allow ISAKMP, ESP, and GRE traffic inbound. !--- Cisco IOS Firewall opens inbound access as needed. access-list 100 permit udp any host 14.24.116.1 eq 500 access-list 100 premit esp any host 14.24.116.1 access-list 100 permit gre any host 14.24.116.1 access-list 100 deny ip any any access-list 110 permit ip 192.168.120.0 0.0.0.255 any !--- Except the private network traffic from the NAT process. access-list 110 deny ip 192.168.120.0 0.0.0.255 192.168.116.0 0.0.0.255 access-list 110 deny ip 192.168.120.0 0.0.0.255 192.168.117.0 0.0.0.255 access-list 110 deny ip 192.168.120.0 0.0.0.255 192.168.118.0 0.0.0.255 access-list 110 permit ip 192.168.120.0 0.0.0.255 any ! !--- Except the private network traffic from the NAT process. route-map nonat permit 10 match ip address 110 ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! end W2N-6.16-1720-A# |
Verify
Use this section to confirm that your configuration works properly.
The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
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show crypto isakmp sa—Displays the state for the ISAKMP security association (SA).
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show crypto engine connections active—Displays the total encrypts/decrypts per SA.
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show crypto ipsec sa—Displays the statistics on the active tunnels.
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show ip route—Displays the routing table.
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show ip ospf neighbor—Displays OSPF neighbor information on a per-interface basis.
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show ip nhrp—Displays the IP Next Hop Resolution Protocol (NHRP) cache, optionally limited to dynamic or static cache entries for a specific interface.
Troubleshoot
This section provides information you can use to troubleshoot your configuration.
Troubleshooting Commands
Note: Refer to Important Information on Debug Commands before you issue debug commands.
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debug crypto ipsec—Displays IPsec events.
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debug crypto isakmp—Displays messages about IKE events.
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debug crypto engine—Displays information from the crypto engine.
Additional information on troubleshooting IPsec can be found at IP Security Troubleshooting - Understanding and Using debug commands.
Related Information
Revision History
| Revision | Publish Date | Comments |
|---|---|---|
1.0 |
28-May-2003 |
Initial Release |
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