As for any IPsec VPN we need to add ISAKMP (phase1 ):
! crypto isakmp policy 1 encr aes authentication pre-share group 2 !
In next step I add pool with IP addresses that will be allocated for users:
! ip local pool POOL 126.96.36.199 188.8.131.52 ! crypto isakmp client configuration address-pool local POOL !
Now I add client configuration group:
! crypto isakmp client configuration group CG key cisco pool POOL !
I can now add this group to aaa configuration:
! aaa new-model ! aaa authorization network AUTH-LIST local !
I have to specify where is the user database (local/ACS/etc):
aaa authentication login USERS local username cisco password 0 cisco
The ISAKMP part is completed and now I can IPsec transform set:
crypto ipsec transform-set TS esp-aes 256 esp-sha-hmac
and then crypto map:
crypto dynamic-map DMAP 1 set transform-set TS reverse-route ! crypto map MAP 1 ipsec-isakmp dynamic DMAP !
And then I can map client authentication and isakmp authorization lists to my crypto map:
crypto map MAP client authentication list USERS crypto map MAP isakmp authorization list AUTH-LIST crypto map MAP client configuration address respond
The last step is applying the map on the interface:
! interface FastEthernet0/0 crypto map MAP !
I need to know add three loopback interfaces to simulate different LANs:
! interface Loopback7 ip address 184.108.40.206 255.255.255.0 ! interface Loopback8 ip address 220.127.116.11 255.255.255.0 ! interface Loopback9 ip address 18.104.22.168 255.255.255.0 !
Let’s test it. Client settings:
Ok, the tunnel is up:
R14#sh crypto isakmp saIPv4 Crypto ISAKMP SA dst src state conn-id status 10.0.0.2 192.168.202.147 QM_IDLE 1002 ACTIVE IPv6 Crypto ISAKMP SA R14#
Looking on the routing details you can notice that all traffic (0.0.0.0) is going be secured:
R14#sh crypto session d Crypto session current status Code: C - IKE Configuration mode, D - Dead Peer Detection K - Keepalives, N - NAT-traversal, T - cTCP encapsulation X - IKE Extended Authentication, F - IKE Fragmentation Interface: FastEthernet0/0 Username: cisco Group: CG Assigned address: 22.214.171.124 Uptime: 00:23:05 Session status: UP-ACTIVE Peer: 192.168.202.147 port 49685 fvrf: (none) ivrf: (none) Phase1_id: CG Desc: (none) IKEv1 SA: local 10.0.0.2/500 remote 192.168.202.147/49685 Active Capabilities:CX connid:1002 lifetime:23:36:44 IPSEC FLOW: permit ip 0.0.0.0/0.0.0.0 host 126.96.36.199 Active SAs: 2, origin: dynamic crypto map Inbound: #pkts dec'ed 182 drop 0 life (KB/Sec) 4203360/2214 Outbound: #pkts enc'ed 149 drop 0 life (KB/Sec) 4203375/2214 R14#
I check if I can access all three loopbacks:
And I see packets incremented when I ping these IPs.
Now I would like to change the scenario a bit by excluding loopback9 (188.8.131.52) from encryption but still be able to ping it.
To accomplish it we need to add an access list and specify which IPs should be encrypted:
R14(config)#access-list 101 permit ip host 184.108.40.206 220.127.116.11 0.0.0.255 R14(config)#access-list 101 permit ip host 18.104.22.168 22.214.171.124 0.0.0.255
* do not try here any l4 (will be ignored) access list or deny statement because everything from this acl will be added, permit and deny too (!)
And then the acl needs to be added to the isakmp client configuration:
crypto isakmp client configuration group CG acl 101
I reconnected once again and we can notice that now only specified IPs/subnets are secured and the rest is not (split-tunneling):
As you see pings to 126.96.36.199 and 188.8.131.52 go over the tunnel (packet encrypted/decrypted increased).
Now let’s test 184.108.40.206 that should be sent via the tunnel:
As you see I can ping this IP and I see only more ‘bypassed’ packet. Encrypted/decrypted are still 8.
Now I would like to improve the security and add ACL to protect these two IPs and deny any traffic from the Internet:
- Hosts accessible only via the VPN: 220.127.116.11, 18.104.22.168
- Host accessible from Internet and it shouldn’t never go through the VPN: 22.214.171.124
! ip access-list extended OUTSIDE permit icmp any host 126.96.36.199 log permit udp any any eq isakmp log permit esp any any log deny ip any any log ! interface FastEthernet0/0 ip access-group OUTSIDE in !
Let’s test it:
As you see without VPN I can’t ping 188.8.131.52 and 184.108.40.206. The last one, 220.127.116.11, is accessible as expected.
When the tunnel is up the we can ping hosts 18.104.22.168 and 22.214.171.124 again:
Now I’m going to add LAN host more and it will simulate user computer. This user sending something over the Internet should be nat-ed:
! access-list 10 permit 192.168.1.1 ! ip nat inside source list 10 interface FastEthernet0/0 overload ! interface Loopback10 ip address 192.168.1.1 255.255.255.0 ip nat inside end ! ! interface FastEthernet0/0 ip nat outside !
The one problem is when the VPN user wants to communicate with this LAN user the traffic will be NAT-ed too, what is not what we need:
As you see I’m not able to ping this host. I have to exclude this source/destination pair from being NAT-ed:
! access-list 110 deny ip host 192.168.1.1 126.96.36.199 0.0.0.255 access-list 110 permit ip host 192.168.1.1 any ! ip nat inside source list 110 interface FastEthernet0/0 overload !
Let’s test if nat still works:
R14#ping 10.0.0.1 source loo10 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds: Packet sent with a source address of 192.168.1.1 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 28/50/68 ms R14#sh ip nat translations Pro Inside global Inside local Outside local Outside global icmp 10.0.0.2:1024 192.168.1.1:6 10.0.0.1:6 10.0.0.1:1024 R14#
Let’s test again communication between VPN and LAN users:
As you see everything works as expected.
Now I would like to add another requirement:
- Vpn users should be able to ping both hosts but telnet to only 188.8.131.52