IPsec VPN Configuration On Cisco IOS XE - Part 3 - Route Based VPN
There are two Route Based IPsec VPN tunnels configured on CSR1000V router, traffic from app server is with NAT and rest is without NAT.
This is the third article in series about configuring VPN tunnels in IOS XE. [ Link to Part 1 ] [ Link to Part 2 ]
In the previous two parts, I configured simple policy-based VPN tunnels. In this article, I will show how to build a route-based VPN tunnel.
This is an imaginary setup of a company which has Data Centre (DC) with Application and Storage servers. And two sites (a and b) connect to DC via IPSEC VPN tunnels with the Internet as an underlay. Details of IP addresses and device connections are shown in the diagram.
Goals of this scenario are -
1) Create Route-based IPSec VPN tunnel between "dc-gw1" in DC to "site-a-gw1" in site A.
2) Create Route-based IPSec VPN tunnel between "dc-gw1" in DC to "site-b-gw1" in site B.
3) Traffic between "app1" server to "user" will be NATed. We have to configure "inside" and "outside" NAT.
Router IOS version used for this setup are -
dc-gw1 = Cisco IOS Software, CSR1000V Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 15.4(2)S, RELEASE SOFTWARE (fc2)
site-a-gw1 and site-b-gw1 = Cisco IOS Software, 7200 Software (C7200-ADVENTERPRISEK9-M), Version 12.4(24)T, RELEASE SOFTWARE (fc1)
I had configured Interface IP's on DC router and site routers and implemented default route towards Internet router. This simulates underlay Internet links for DC and sites.
Interface And Route Configuration On DC Router = "dc-gw1"
| interface GigabitEthernet1 platform ring rx 256 ip address 10.0.0.2 255.255.255.252 negotiation auto interface GigabitEthernet2 platform ring rx 256 ip address 100.0.20.1 255.255.255.0 secondary ip address 100.0.10.1 255.255.255.0 ip nat inside negotiation auto ip route 0.0.0.0 0.0.0.0 10.0.0.1 ip route 172.17.10.0 255.255.255.0 172.20.10.2 ip route 192.168.10.0 255.255.255.0 172.20.10.2 ip route 192.168.20.0 255.255.255.0 172.20.20.2 |
Interface And Route Configuration On site A Router = "site-a-gw1"
| interface GigabitEthernet0/0 ip address 20.0.0.2 255.255.255.252 duplex full speed 1000 media-type gbic negotiation auto interface GigabitEthernet1/0 ip address 192.168.10.1 255.255.255.0 negotiation auto ip route 0.0.0.0 0.0.0.0 20.0.0.1 ip route 100.0.20.0 255.255.255.0 172.20.10.1 ip route 172.16.10.0 255.255.255.0 172.20.10.1 |
Interface And Route Configuration On site B Router = "site-b-gw1"
| interface GigabitEthernet0/0 ip address 30.0.0.2 255.255.255.252 duplex full speed 1000 media-type gbic negotiation auto interface GigabitEthernet1/0 ip address 192.168.20.1 255.255.255.0 negotiation auto ip route 0.0.0.0 0.0.0.0 30.0.0.1 ip route 100.0.10.0 255.255.255.0 172.20.20.1 ip route 100.0.20.0 255.255.255.0 172.20.20.1 |
Next is Route-based IPsec VPN configuration for DC router and site routers.
IPsec VPN Configuration On DC Router = "dc-gw1"
| crypto keyring site-a pre-shared-key address 20.0.0.2 key acme crypto keyring site-b pre-shared-key address 30.0.0.2 key acme crypto isakmp policy 10 encr aes 256 authentication pre-share group 14 crypto ipsec transform-set AES-256-SHA esp-aes 256 esp-sha-hmac mode tunnel crypto ipsec profile tunnel-to-site-a set transform-set AES-256-SHA crypto ipsec profile tunnel-to-site-b set transform-set AES-256-SHA interface Tunnel1 description Tunnel to Site A ip address 172.20.10.1 255.255.255.252 ip nat outside tunnel source 10.0.0.2 tunnel mode ipsec ipv4 tunnel destination 20.0.0.2 tunnel protection ipsec profile tunnel-to-site-a interface Tunnel2 description Tunnel to Site B ip address 172.20.20.1 255.255.255.252 tunnel source 10.0.0.2 tunnel mode ipsec ipv4 tunnel destination 30.0.0.2 tunnel protection ipsec profile tunnel-to-site-b |
IPsec VPN Configuration On site A Router = "site-a-gw1"
| crypto isakmp policy 10 encr aes 256 authentication pre-share group 14 crypto isakmp key acme address 10.0.0.2 crypto ipsec transform-set AES-256-SHA esp-aes 256 esp-sha-hmac crypto ipsec profile tunnel-to-dc set transform-set AES-256-SHA interface Tunnel1 description Tunnel to DC ip address 172.20.10.2 255.255.255.252 tunnel source 20.0.0.2 tunnel destination 10.0.0.2 tunnel mode ipsec ipv4 tunnel protection ipsec profile tunnel-to-dc |
IPsec VPN Configuration On site B Router = "site-b-gw1"
| crypto isakmp policy 10 encr aes 256 authentication pre-share group 14 crypto isakmp key acme address 10.0.0.2 crypto ipsec transform-set AES-256-SHA esp-aes 256 esp-sha-hmac crypto ipsec profile tunnel-to-dc set transform-set AES-256-SHA interface Tunnel2 description Tunnel to DC ip address 172.20.20.2 255.255.255.252 tunnel source 30.0.0.2 tunnel destination 10.0.0.2 tunnel mode ipsec ipv4 tunnel protection ipsec profile tunnel-to-dc |
This completes our goals 1 and 2 and we have VPN tunnels between DC and sites. The next part is about implementing NAT on DC router.
This NAT will change App server IP from 100.0.10.10 to 172.16.10.10
I did not use the "ip nat outside" command for this NAT, because I want to keep traffic between Storage server to site-A user without NAT.
| ip nat pool source-nat-pool 172.16.10.10 172.16.10.10 prefix-length 30 ip access-list extended source-nat-acl permit ip host 100.0.10.10 host 172.17.10.10 log route-map source-nat-routemap permit 10 match ip address source-nat-acl ip nat inside source route-map source-nat-routemap pool source-nat-pool |
And this NAT configuration will change site user IP from 172.17.10.10 to 192.168.10.10.
| ip nat outside source static 192.168.10.10 172.17.10.10 |
And here are the ping commands to generate traffic.
| app1> ping 192.168.20.10 84 bytes from 192.168.20.10 icmp_seq=1 ttl=62 time=41.008 ms 84 bytes from 192.168.20.10 icmp_seq=2 ttl=62 time=38.508 ms 84 bytes from 192.168.20.10 icmp_seq=3 ttl=62 time=50.510 ms 84 bytes from 192.168.20.10 icmp_seq=4 ttl=62 time=39.508 ms 84 bytes from 192.168.20.10 icmp_seq=5 ttl=62 time=33.006 ms app1> ping 192.168.10.10 192.168.10.10 icmp_seq=1 timeout 192.168.10.10 icmp_seq=2 timeout 192.168.10.10 icmp_seq=3 timeout 192.168.10.10 icmp_seq=4 timeout 192.168.10.10 icmp_seq=5 timeout app1> ping 172.17.10.10 84 bytes from 172.17.10.10 icmp_seq=1 ttl=62 time=32.006 ms 84 bytes from 172.17.10.10 icmp_seq=2 ttl=62 time=48.510 ms 84 bytes from 172.17.10.10 icmp_seq=3 ttl=62 time=30.506 ms 84 bytes from 172.17.10.10 icmp_seq=4 ttl=62 time=27.005 ms 84 bytes from 172.17.10.10 icmp_seq=5 ttl=62 time=34.507 ms |
This traffic created NAT translation table entries as below.
| dc-gw1#sh ip nat translations Pro Inside global Inside local Outside local Outside global --- --- --- 172.17.10.10 192.168.10.10 icmp 172.16.10.10:61400 100.0.10.10:61400 172.17.10.10:61400 192.168.10.10:61400 icmp 172.16.10.10:61656 100.0.10.10:61656 172.17.10.10:61656 192.168.10.10:61656 icmp 172.16.10.10:62168 100.0.10.10:62168 172.17.10.10:62168 192.168.10.10:62168 icmp 172.16.10.10:61144 100.0.10.10:61144 172.17.10.10:61144 192.168.10.10:61144 icmp 172.16.10.10:61912 100.0.10.10:61912 172.17.10.10:61912 192.168.10.10:61912 Total number of translations: 6 |
These ping results and NAT translation entries show connections between app server in DC and user computer in site sites.
Please note that:
1) When a packet generated by app server it does have a source IP 100.0.10.10, when this packet reaches DC router, it gets changed into 172.16.10.10.
2) The same packet generated by app server it does have destination IP 172.17.10.10, when this packet reaches DC router, it gets changed into 192.168.10.10.
3) After both inside (source IP) and outside (destination IP) are changed, this packet enters VPN tunnel.
This is the end of Part 3 of this series, we have seen basic route-based VPN setup and its sample configuration. Anyone who is working on VPN setup using Cisco routers with IOS XE may use this configuration.
In the next article, we will be configuring Route Based VPN tunnels with a dynamic routing protocol.
Link to the next article in this series = Part 4 - Route Based VPN With Dynamic Routing (OSPF)
I hope you find this helpful.
Have a question about something in this article? You can receive help directly from the article author. Sign up for a free trial to get started.
Comments (0)