Document ID: 117257
Updated: Jan 21, 2014
Contributed by Michal Garcarz and Olivier Pelerin, Cisco TAC Engineers.
Contents
Introduction
This document describes how to configure strongSwan as a remote access IPSec VPN client that connects to Cisco IOS® software.
strongSwan is open source software that is used in order to build Internet Key Exchange (IKE)/IPSec VPN tunnels and to build LAN-to-LAN and Remote Access tunnels with Cisco IOS software.
Prerequisites
Requirements
Cisco recommends that you have basic knowledge of these topics:
- Linux configuration
- VPN configuration on Cisco IOS software
Components Used
The information in this document is based on these software versions:
- Cisco IOS Software Release 15.3T
- strongSwan 5.0.4
- Linux kernel 3.2.12
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.
Configure
Topology
The remote client receives an IP address from pool 10.10.0.0/16. Traffic between 10.10.0.0/16 and 192.168.1.0/24 is protected.
Configure Cisco IOS Software
In this example, the strongSwan client needs secure access to Cisco IOS software LAN network 192.168.1.0/24. The remote client uses the group name of RA (this is the IKEID) as well as the username of cisco and password of Cisco.
The client gets the IP address from the pool 10.10.0.0/16. Also, the split Access Control List (ACL) is pushed to the client; that ACL will force the client to send traffic to 192.168.1.0/24 via the VPN.
aaa new-model
aaa authentication login AUTH local
aaa authorization network NET local
username cisco password 0 cisco
crypto isakmp policy 1
encryption aes
hash sha
authentication pre-share
group 2
lifetime 3600
crypto isakmp keepalive 10
crypto isakmp client configuration group RA
key cisco
domain cisco.com
pool POOL
acl split
save-password
netmask 255.255.255.0
crypto isakmp profile test
match identity group RA
client authentication list AUTH
isakmp authorization list NET
client configuration address respond
client configuration group RA
virtual-template 1
crypto ipsec transform-set test esp-aes esp-sha-hmac
mode tunnel
crypto ipsec profile ipsecprof
set security-association lifetime kilobytes disable
set transform-set test
set isakmp-profile test
interface GigabitEthernet0/1
ip address 10.48.67.167 255.255.254.0
!
interface GigabitEthernet0/2
description LAN
ip address 192.168.1.1 255.255.255.0
interface Virtual-Template1 type tunnel
ip unnumbered GigabitEthernet0/1
tunnel source GigabitEthernet0/1
tunnel mode ipsec ipv4
tunnel protection ipsec profile ipsecprof
ip local pool POOL 10.10.0.0 10.10.255.255
ip access-list extended split
permit ip host 192.168.1.1 any
Cisco recommends that you do not assign the usual static IP address on a Virtual-Template. The Virtual-Access interfaces are cloned and inherit their configuration from the parent Virtual-Template, which could create duplicate IP addresses. However, the Virtual-Template does refer to an IP address through the 'ip unnumbered' keyword in order to populate the adjacency table. The 'ip unnumbered' keyword is just a reference to a physical or logical IP address on the router.
For forward compatibility with IKE routing in IKEv2, use an inside address, and avoid use of the IPSec 'local address' as 'ip unnumbered.'
Configure strongSwan
This procedure describes how to configure strongSwan:
- Use this configuration in the /etc/ipsec.conf file:
version 2
The rightsubnet keyword has been set in order to indicate which traffic should be protected. In this scenario, the IPSec security association (SA) is built between 192.168.1.0/24 (on Cisco IOS software) and the strongSwan IP address, which is received from pool 10.10.0.0/16.
config setup
strictcrlpolicy=no
charondebug="ike 4, knl 4, cfg 2" #useful debugs
conn %default
ikelifetime=1440m
keylife=60m
rekeymargin=3m
keyingtries=1
keyexchange=ikev1
authby=xauthpsk
conn "ezvpn"
keyexchange=ikev1
ikelifetime=1440m
keylife=60m
aggressive=yes
ike=aes-sha1-modp1024 #Phase1 parameters
esp=aes-sha1 #Phase2 parameters
xauth=client #Xauth client mode
left=10.48.62.178 #local IP used to connect to IOS
leftid=RA #IKEID (group name) used for IOS
leftsourceip=%config #apply received IP
leftauth=psk
rightauth=psk
leftauth2=xauth #use PSK for group RA and Xauth for user cisco
right=10.48.67.167 #gateway (IOS) IP
rightsubnet=192.168.1.0/24
xauth_identity=cisco #identity for Xauth, password in ipsec.secrets
auto=add
Without rightsubnet specified, you might expect to have the 0.0.0.0 network and the IPSec SA between the client IP address and the 0.0.0.0 network. That is the behavior when Cisco IOS software is used as a client.
But this expectation is not correct for strongSwan. Without rightsubnet defined, strongSwan proposes an external gateway (Cisco IOS software) IP address in phase2 of the negotiation; in this scenario, that gateway is 10.48.67.167. Because the goal is to protect traffic that is going to an internal LAN on Cisco IOS software (192.168.1.0/24) and not to an external Cisco IOS software IP address, rightsubnet has been used.
- Use this configuration in the /etc/ipsec.secrets file:
10.48.67.167 : PSK "cisco" #this is PSK for group password
cisco : XAUTH "cisco" #this is password for XAuth (user cisco)
Verify
Use this section in order to confirm that your configuration works properly.
This procedure describes how to test and verify the strongSwan configuration:
- Start strongSwan with debugs enabled:
gentoo1 ~ # /etc/init.d/ipsec start
* Starting ...
Starting strongSwan 5.0.4 IPsec [starter]...
Loading config setup
strictcrlpolicy=no
charondebug=ike 4, knl 4, cfg 2
Loading conn %default
ikelifetime=1440m
keylife=60m
rekeymargin=3m
keyingtries=1
keyexchange=ikev1
authby=xauthpsk
Loading conn 'ezvpn'
keyexchange=ikev1
ikelifetime=1440m
keylife=60m
aggressive=yes
ike=aes-sha1-modp1024
esp=aes-sha1
xauth=client
left=10.48.62.178
leftid=RA
leftsourceip=%config
leftauth=psk
rightauth=psk
leftauth2=xauth
right=10.48.67.167
rightsubnet=192.168.1.0/24
xauth_identity=cisco
auto=add
found netkey IPsec stack
No leaks detected, 9 suppressed by whitelist - When the tunnel from strongSwan is initiated, all general information on phase1, Xauth, and phase2 is displayed:
gentoo1 ~ # ipsec up ezvpn
initiating Aggressive Mode IKE_SA ezvpn[1] to 10.48.67.167
generating AGGRESSIVE request 0 [ SA KE No ID V V V V ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (374 bytes)
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (404 bytes)
parsed AGGRESSIVE response 0 [ SA V V V V V KE ID No HASH NAT-D NAT-D ]
received Cisco Unity vendor ID
received DPD vendor ID
received unknown vendor ID: 8d:75:b5:f8:ba:45:4c:6b:02:ac:bb:09:84:13:32:3b
received XAuth vendor ID
received NAT-T (RFC 3947) vendor ID
generating AGGRESSIVE request 0 [ NAT-D NAT-D HASH ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (92 bytes)
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (92 bytes)
parsed INFORMATIONAL_V1 request 3265561043 [ HASH N((24576)) ]
received (24576) notify
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (68 bytes)
parsed TRANSACTION request 4105447864 [ HASH CP ]
generating TRANSACTION response 4105447864 [ HASH CP ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (76 bytes)
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (68 bytes)
parsed TRANSACTION request 1681157416 [ HASH CP ]
XAuth authentication of 'cisco' (myself) successful
IKE_SA ezvpn[1] established between 10.48.62.178[RA]...10.48.67.167[10.48.67.167]
scheduling reauthentication in 86210s
maximum IKE_SA lifetime 86390s
generating TRANSACTION response 1681157416 [ HASH CP ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (68 bytes)
generating TRANSACTION request 1406391467 [ HASH CP ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (68 bytes)
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (68 bytes)
parsed TRANSACTION response 1406391467 [ HASH CP ]
installing new virtual IP 10.10.0.1
generating QUICK_MODE request 1397274205 [ HASH SA No ID ID ]
sending packet: from 10.48.62.178[500] to 10.48.67.167[500] (196 bytes)
received packet: from 10.48.67.167[500] to 10.48.62.178[500] (180 bytes)
parsed QUICK_MODE response 1397274205 [ HASH SA No ID ID N((24576)) ]
connection 'ezvpn' established successfully
No leaks detected, 1 suppressed by whitelist - When you enable debugs on strongSwan, much information can be returned. This is the most important debug to use when the tunnel is initiated:
#IKE Phase
06[CFG] received stroke: initiate 'ezvpn'
04[IKE] initiating Aggressive Mode IKE_SA ezvpn[1] to 10.48.67.167
03[CFG] proposal matches
03[CFG] received proposals: IKE:AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
03[CFG] selected proposal: IKE:AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
16[IKE] IKE_SA ezvpn[1] state change: CONNECTING => ESTABLISHED
16[IKE] scheduling reauthentication in 86210s
#Xauth phase
15[KNL] 10.48.62.178 is on interface eth1
15[IKE] installing new virtual IP 10.10.0.1
15[KNL] virtual IP 10.10.0.1 installed on eth1
#Ipsec
05[CFG] proposal matches
05[CFG] received proposals: ESP:AES_CBC_128/HMAC_SHA1_96/NO_EXT_SEQ
05[CFG] selected proposal: ESP:AES_CBC_128/HMAC_SHA1_96/NO_EXT_SEQ
05[KNL] adding SAD entry with SPI 7600acd8 and reqid
15[CFG] proposing traffic selectors for us:
15[CFG] 10.10.0.1/32
15[CFG] proposing traffic selectors for other:
15[CFG] 192.168.1.0/24
#Local settings
charon: 05[KNL] getting a local address in traffic selector 10.10.0.1/32
charon: 05[KNL] using host 10.10.0.1
charon: 05[KNL] using 10.48.62.129 as nexthop to reach 10.48.67.167
charon: 05[KNL] 10.48.62.178 is on interface eth1
charon: 05[KNL] installing route: 192.168.1.0/24 via 10.48.62.129 src 10.10.0.1
dev eth1
charon: 05[KNL] getting iface index for eth1
charon: 05[KNL] policy 10.10.0.1/32 === 192.168.1.0/24 out (mark 0/0x00000000)
already exists, increasing refcount
charon: 05[KNL] updating policy 10.10.0.1/32 === 192.168.1.0/24 out - Send traffic from the client:
gentoo1 ~ # ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_req=1 ttl=255 time=1.19 ms
64 bytes from 192.168.1.1: icmp_req=2 ttl=255 time=1.19 ms
64 bytes from 192.168.1.1: icmp_req=3 ttl=255 time=1.12 ms
64 bytes from 192.168.1.1: icmp_req=4 ttl=255 time=1.16 ms
64 bytes from 192.168.1.1: icmp_req=4 ttl=255 time=1.26 ms
^C
--- 192.168.1.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 1.128/1.171/1.199/0.036 ms - Check the dynamic interface on Cisco IOS software:
Bsns-7200-2#sh int Virtual-Access1
Virtual-Access1 is up, line protocol is up
Hardware is Virtual Access interface
Interface is unnumbered. Using address of GigabitEthernet0/1 (10.48.67.167)
MTU 17878 bytes, BW 100000 Kbit/sec, DLY 50000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL
Tunnel vaccess, cloned from Virtual-Template1
Vaccess status 0x4, loopback not set
Keepalive not set
Tunnel source 10.48.67.167 (GigabitEthernet0/1), destination 10.48.62.178
Tunnel Subblocks:
src-track:
Virtual-Access1 source tracking subblock associated with
GigabitEthernet0/1
Set of tunnels with source GigabitEthernet0/1, 2 members (includes
iterators), on interface <OK>
Tunnel protocol/transport IPSEC/IP
Tunnel TTL 255
Tunnel transport MTU 1438 bytes
Tunnel transmit bandwidth 8000 (kbps)
Tunnel receive bandwidth 8000 (kbps)
Tunnel protection via IPSec (profile "ipsecprof")
Last input never, output never, output hang never
Last clearing of "show interface" counters 00:07:19
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
5 packets input, 420 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
5 packets output, 420 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out - Check the IPSec counters on Cisco IOS software:
Bsns-7200-2#show crypto session detail
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: Virtual-Access1
Username: cisco
Profile: test
Group: RA
Assigned address: 10.10.0.1
Uptime: 00:39:25
Session status: UP-ACTIVE
Peer: 10.48.62.178 port 500 fvrf: (none) ivrf: (none)
Phase1_id: RA
Desc: (none)
IKEv1 SA: local 10.48.67.167/500 remote 10.48.62.178/500 Active
Capabilities:CDX connid:13002 lifetime:00:20:34
IPSEC FLOW: permit ip 192.168.1.0/255.255.255.0 host 10.10.0.1
Active SAs: 2, origin: crypto map
Inbound: #pkts dec'ed 5 drop 0 life (KB/Sec) KB Vol Rekey Disabled/1234
Outbound: #pkts enc'ed 5 drop 0 life (KB/Sec) KB Vol Rekey Disabled/1234 - Verify status on strongSwan:
gentoo1 ~ # ipsec statusall
Status of IKE charon daemon (strongSwan 5.0.4, Linux 3.2.12-gentoo, x86_64):
uptime: 41 minutes, since Jun 09 10:45:59 2013
malloc: sbrk 1069056, mmap 0, used 896944, free 172112
worker threads: 7 of 16 idle, 8/1/0/0 working, job queue: 0/0/0/0, scheduled: 2
loaded plugins: charon aes des sha1 sha2 md5 random nonce x509 revocation
constraints pubkey pkcs1 pkcs8 pgp dnskey pem openssl gcrypt fips-prf gmp
xcbc cmac hmac attr kernel-netlink resolve socket-default stroke updown
eap-identity eap-sim eap-aka eap-aka-3gpp2 eap-simaka-pseudonym
eap-simaka-reauth eap-md5 eap-gtc eap-mschapv2 eap-radius xauth-generic dhcp
Listening IP addresses:
192.168.0.10
10.48.62.178
2001:420:44ff:ff61:250:56ff:fe99:7661
192.168.2.1
Connections:
ezvpn: 10.48.62.178...10.48.67.167 IKEv1 Aggressive
ezvpn: local: [RA] uses pre-shared key authentication
ezvpn: local: [RA] uses XAuth authentication: any with XAuth identity
'cisco'
ezvpn: remote: [10.48.67.167] uses pre-shared key authentication
ezvpn: child: dynamic === 192.168.1.0/24 TUNNEL
Security Associations (1 up, 0 connecting):
ezvpn[1]: ESTABLISHED 41 minutes ago, 10.48.62.178[RA]...
10.48.67.167[10.48.67.167]
ezvpn[1]: IKEv1 SPIs: 0fa722d2f09bffe0_i* 6b4c44bae512b278_r, pre-shared
key+XAuth reauthentication in 23 hours
ezvpn[1]: IKE proposal: AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
ezvpn{1}: INSTALLED, TUNNEL, ESP SPIs: c805b9ba_i 7600acd8_o
ezvpn{1}: AES_CBC_128/HMAC_SHA1_96, 420 bytes_i (5 pkts, 137s ago), 420
bytes_o (5 pkts, 137s ago), rekeying in 13 minutes
ezvpn{1}: 10.10.0.1/32 === 192.168.1.0/24
No leaks detected, 1 suppressed by whitelist
Troubleshoot
There is currently no specific troubleshooting information available for this configuration.
Summary
This document described the configuration of a strongSwan client that connects as an IPSec VPN client to Cisco IOS software.
It is also possible to configure an IPSec LAN-to-LAN tunnel between Cisco IOS software and strongSwan. Additionally, IKEv2 between both devices works correctly both for remote and LAN-to-LAN access.
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Updated: Jan 21, 2014
Document ID: 117257