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Here it comes. We will use the same topology as the last two blog posts. This time we will play with GETVPN. GETVPN is a Cisco technology. One of the advantage of GETVPN is that we are able to build somespoke-to-spoke IPSEC tunnel without Tunnel interface and it is highly scalable. |
We could say to me : ok, man ! but you could do this by means of static tunnels. Yes you can, BUT with GETVPN you can maintain easily full mesh networks by means of Key Server and the GETVPN technology.
Tunnel is build between GM (Group Member). The Key Server (KS) maintains security policies and is not part of the Forwarding Path. This server is here to provide security policy and make it possible to GM to build a encrypted tunnel between each other. No need to pass through a central node. GETVPN is a answer, DMVPN phase 3 is another 🙂
We have R4 as KS with a loopback address : 4.4.4.4/32
We have R2 and R3 as our spokes. These routers has each other a loopback 99 with a different /24 subnet.
- R2 : 99.99.99.0/24
- R3 : 100.100.100.0/24
Let’s go and see how it is configured. Begin with the Key Server :
crypto key generate rsa modulus 1024 label REKEYRSA crypto isakmp policy 1 encr 3des authentication pre-share group 2 crypto isakmp key cisco address 0.0.0.0 crypto ipsec transform-set SET esp-3des esp-md5-hmac mode tunnel crypto ipsec profile PROFILE set transform-set SET crypto gdoi group GDOI-GROUP1 identity number 12345 server local rekey algorithm aes 128 rekey authentication mypubkey rsa REKEYRSA rekey transport unicast sa ipsec 1 profile PROFILE match address ipv4 getvpn-acl replay time window-size 5 no tag address ipv4 4.4.4.4 ip access-list extended getvpn-acl permit ip 99.99.99.0 0.0.0.255 100.100.100.0 0.0.0.255 permit ip 100.100.100.0 0.0.0.255 99.99.99.0 0.0.0.255 deny ip any any
Now R2 and R3 :
R2 : crypto isakmp policy 1 encr 3des authentication pre-share group 2 crypto isakmp key cisco address 0.0.0.0 crypto ipsec transform-set SET esp-3des esp-md5-hmac mode tunnel crypto ipsec profile PROFILE set transform-set SET crypto gdoi group GDOI-GROUP1 identity number 12345 server address ipv4 4.4.4.4 crypto map gdoimap 1 gdoi set group GDOI-GROUP1 crypto map gdoimap interface Ethernet0/1 ip address 123.0.0.2 255.255.255.0 ip router isis crypto map gdoimap
R3 : crypto isakmp policy 1 encr 3des authentication pre-share group 2 crypto isakmp key cisco address 0.0.0.0 crypto ipsec transform-set SET esp-3des esp-md5-hmac mode tunnel crypto ipsec profile PROFILE set transform-set SET crypto gdoi group GDOI-GROUP1 identity number 12345 server address ipv4 4.4.4.4 crypto map gdoimap 1 gdoi set group GDOI-GROUP1 crypto map gdoimap
GM use and interact with the KS to build their IPSec SA. Here, the security policy is identified by “identity number 12345”.
To make my topology works I have been obliged to add a static route towards my remote endpoints. I have been obliged to due to a bug on my IOS. It crashes if I add a “reverse-route” command in my crypto map.
Now, we could try to ping each other :
R2# ping 100.100.100.3 so lo 99 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 100.100.100.3, timeout is 2 seconds: Packet sent with a source address of 99.99.99.2 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/7 ms R2#
Good ! it pings. Let’s see if it is encrypted :
https://www.cloudshark.org/captures/a99bd1404eaa or http://www.clucas.fr/downloads/GETVPN.pcap
Great it works 🙂
Now see some troubleshooting commands :
R2#show crypto session
Crypto session current status
Interface: Ethernet0/1
Session status: UP-ACTIVE
Peer: 0.0.0.0 port 500
Session ID: 0
IKEv1 SA: local 123.0.0.2/848 remote 4.4.4.4/848 Active
IPSEC FLOW: deny ip 0.0.0.0/0.0.0.0 0.0.0.0/0.0.0.0
Active SAs: 0, origin: crypto map
IPSEC FLOW: permit ip 100.100.100.0/255.255.255.0 99.99.99.0/255.255.255.0
Active SAs: 2, origin: crypto map
IPSEC FLOW: permit ip 99.99.99.0/255.255.255.0 100.100.100.0/255.255.255.0
Active SAs: 2, origin: crypto map
R2#
R2#show crypto gdoi gm
Group Member Information For Group GDOI-GROUP1:
IPSec SA Direction : Both
ACL Received From KS : gdoi_group_GDOI-GROUP1_temp_acl
Group member : 123.0.0.2 vrf: None
Local addr/port : 123.0.0.2/848
Remote addr/port : 4.4.4.4/848
fvrf/ivrf : None/None
Version : 1.0.8
Registration status : Registered
Registered with : 4.4.4.4
Re-registers in : 2673 sec
Succeeded registration: 1
Attempted registration: 1
Last rekey from : 4.4.4.4
Last rekey seq num : 10
Unicast rekey received: 2
Rekey ACKs sent : 2
Rekey Rcvd(hh:mm:ss) : 00:11:50
DP Error Monitoring : OFF
R2#
R2# show crypto ipsec sa
interface: Ethernet0/1
Crypto map tag: gdoimap, local addr 123.0.0.2
protected vrf: (none)
local ident (addr/mask/prot/port): (100.100.100.0/255.255.255.0/0/0)
remote ident (addr/mask/prot/port): (99.99.99.0/255.255.255.0/0/0)
Group: GDOI-GROUP1
current_peer 0.0.0.0 port 848
PERMIT, flags={}
#pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0
#pkts decaps: 25, #pkts decrypt: 25, #pkts verify: 25
[...]
protected vrf: (none)
local ident (addr/mask/prot/port): (99.99.99.0/255.255.255.0/0/0)
remote ident (addr/mask/prot/port): (100.100.100.0/255.255.255.0/0/0)
Group: GDOI-GROUP1
current_peer 0.0.0.0 port 848
PERMIT, flags={}
#pkts encaps: 25, #pkts encrypt: 25, #pkts digest: 25
#pkts decaps: 0, #pkts decrypt: 0, #pkts verify: 0
[...]
Ok each SA encrypt and decrypts the correct number of packets 🙂
KS side :
R4#show crypto gdoi ks
Total group members registered to this box: 2
Key Server Information For Group GDOI-GROUP1:
Group Name : GDOI-GROUP1
Re-auth on new CRL : Disabled
Group Identity : 12345
Group Members : 2
IPSec SA Direction : Both
ACL Configured:
access-list getvpn-acl
R4#show crypto gdoi ks acl
Group Name: GDOI-GROUP1
Configured ACL:
access-list getvpn-acl permit ip 99.99.99.0 0.0.0.255 100.100.100.0 0.0.0.255
access-list getvpn-acl permit ip 100.100.100.0 0.0.0.255 99.99.99.0 0.0.0.255
access-list getvpn-acl deny ip any any
R4#
For more information : http://www.cisco.com/c/en/us/products/collateral/security/group-encrypted-transport-vpn/deployment_guide_c07_554713.html
Have fun with GETVPN !!