Document ID: 9353
Updated: Nov 04, 2002
Contents
Introduction
This document illustrates an IP Security (IPSec) configuration between a router and a Cisco Secure PIX Firewall. We want to use private internal IP addresses when passing traffic between the headquarters LAN and the remote LANs, and to translate the LAN hosts to routable IP addresses when users access the Internet. However, users can also access public pages on the Internet without their traffic going through the tunnel using the route-map command.
Refer to ASA/PIX : Security Appliance to an IOS Router LAN-to-LAN IPsec Tunnel Configuration Example in order to learn more about the scenario where a LAN-to-LAN tunnels between a router and the Cisco Security Appliances PIX/ASA.
Before You Begin
Conventions
For more information on document conventions, see the Cisco Technical Tips Conventions.
Prerequisites
There are no specific prerequisites for this document.
Components Used
The information in this document is based on the software and hardware versions below.
-
Cisco Router with Cisco IOS® Software Release 12.0(7)T
-
Cisco PIX Firewall Version 5.1(1)
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
Background Theory
On the PIX, the access-list and nat 0 commands work together. When a user on the 10.1.1.0 network goes to the 10.2.2.0 network, we use the access list to permit the 10.1.1.0 network traffic to be encrypted without Network Address Translation (NAT). However, when those same users go anywhere else, they are translated to the 172.17.63.210 address through Port Address Translation (PAT). On the router, the route-map and access-list commands are used to permit the 10.2.2.0 network traffic to be encrypted without NAT. However, when those same users go anywhere else, they are translated to the 172.17.63.210 address through Port Address Translation (PAT).
The following are configuration commands required on the PIX firewall in order for traffic not to run through PAT over the tunnel, and traffic to the Internet to run through PAT.
access-list nonat permit ip 10.1.1.0 255.255.255.0 10.2.2.0 255.255.255.0 nat (inside) 0 access-list nonat nat (inside) 1 10.1.1.0 255.255.255.0 0 0
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: To find additional information on the commands used in this document, use the IOS Command Lookup tool.
Network Diagram
This document uses the network setup shown in the diagram below.
Configurations
This document uses the configurations shown below.
| Headquarters PIX |
|---|
PIX Version 5.1(1) nameif ethernet0 outside security0 nameif ethernet1 inside security100 !--- Traffic to the router: access-list ipsec permit ip 10.1.1.0 255.255.255.0 10.2.2.0 255.255.255.0 !--- Do not Network Address Translate (NAT) traffic to the router: access-list nonat permit ip 10.1.1.0 255.255.255.0 10.2.2.0 255.255.255.0 enable password 8Ry2YjIyt7RRXU24 encrypted passwd 2KFQnbNIdI.2KYOU encrypted hostname HQ_PIX fixup protocol ftp 21 fixup protocol http 80 fixup protocol smtp 25 fixup protocol h323 1720 fixup protocol rsh 514 fixup protocol sqlnet 1521 names pager lines 24 no logging timestamp no logging standby no logging console no logging monitor no logging buffered no logging trap no logging history logging facility 20 logging queue 512 interface ethernet0 auto interface ethernet1 auto mtu outside 1500 mtu inside 1500 ip address outside 172.17.63.213 255.255.255.240 ip address inside 10.1.1.1 255.255.255.0 no failover failover timeout 0:00:00 failover ip address outside 0.0.0.0 failover ip address inside 0.0.0.0 arp timeout 14400 global (outside) 1 172.17.63.210 !--- Do not NAT traffic to the router: nat (inside) 0 access-list nonat nat (inside) 1 10.1.1.0 255.255.255.0 0 0 conduit permit icmp any any route outside 0.0.0.0 0.0.0.0 172.17.63.209 1 timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute aaa-server TACACS+ protocol tacacs+ aaa-server RADIUS protocol radius aaa-server partner protocol tacacs+ no snmp-server location no snmp-server contact snmp-server community public no snmp-server enable traps floodguard enable !--- IPSec policies: sysopt connection permit-ipsec crypto ipsec transform-set avalanche esp-des esp-md5-hmac crypto ipsec security-association lifetime seconds 3600 crypto map forsberg 21 ipsec-isakmp crypto map forsberg 21 match address ipsec crypto map forsberg 21 set peer 172.17.63.230 crypto map forsberg 21 set transform-set avalanche crypto map forsberg interface outside !--- IKE policies: isakmp enable outside isakmp key westernfinal2000 address 172.17.63.230 netmask 255.255.255.255 isakmp identity address isakmp policy 21 authentication pre-share isakmp policy 21 encryption des isakmp policy 21 hash md5 isakmp policy 21 group 1 telnet timeout 5 terminal width 80 Cryptochecksum:e36245da9428c4c07b489f787c8ccd3b : end |
| Branch Router |
|---|
Current configuration: ! version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Branch_Router ! ! ! ! ! ! ip subnet-zero ! ! !--- IKE policies: crypto isakmp policy 11 hash md5 authentication pre-share crypto isakmp key westernfinal2000 address 172.17.63.213 ! ! !--- IPSec policies: crypto ipsec transform-set sharks esp-des esp-md5-hmac ! ! crypto map nolan 11 ipsec-isakmp set peer 172.17.63.213 set transform-set sharks !--- Include the private-network-to-private-network traffic !--- in the encryption process. match address 120 ! ! ! interface Ethernet0 ip address 172.17.63.230 255.255.255.240 no ip directed-broadcast ip nat outside no ip route-cache crypto map nolan ! interface Ethernet1 ip address 10.2.2.1 255.255.255.0 no ip directed-broadcast ip nat inside ! interface Serial0 no ip address no ip directed-broadcast no ip mroute-cache shutdown no fair-queue ! interface Serial1 no ip address no ip directed-broadcast shutdown ! ip nat pool branch 172.17.63.230 172.17.63.230 netmask 255.255.255.240 !--- Except the private network from the NAT process: ip nat inside source route-map nonat pool branch overload ip classless ip route 0.0.0.0 0.0.0.0 172.17.63.225 no ip http server !--- Include the private-network-to-private-network traffic !--- in the encryption process: access-list 120 permit ip 10.2.2.0 0.0.0.255 10.1.1.0 0.0.0.255 !--- Except the private network from the NAT process: access-list 130 deny ip 10.2.2.0 0.0.0.255 10.1.1.0 0.0.0.255 access-list 130 permit ip 10.2.2.0 0.0.0.255 any !--- Except the private network from the NAT process: route-map nonat permit 10 match ip address 130 ! ! line con 0 transport input none line 1 16 line aux 0 line vty 0 4 ! end |
Verify
This section provides information you can use to confirm your configuration is working properly.
Certain show commands are supported by the Output Interpreter tool, which allows you to view an analysis of show command output.
-
show crypto isakmp sa - View all current IKE security associations (SAs) at a peer.
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show crypto ipsec sa - Shows the settings used by current [IPSec] security associations.
-
show crypto engine connections active - (Router only) Shows current connections and information regarding encrypted and decrypted packets.
Troubleshoot
This section provides information you can use to troubleshoot your configuration.
Troubleshooting Commands
Certain show commands are supported by the Output Interpreter tool, which allows you to view an analysis of show command output.
Note: Before issuing debug commands, please see Important Information on Debug Commands.
The following debugs must be running on both IPSec peers.
-
debug crypto isakmp - (Router & PIX) Displays errors during Phase 1.
-
debug crypto ipsec - (Router & PIX) Displays errors during Phase 2.
-
debug crypto engine - (Router only) Displays information from the crypto engine.
Clearing security associations must be done on both peers. The PIX commands are performed in enable mode; the router commands are performed in non-enable mode.
-
clear crypto isakmp sa - (PIX) Clears the Phase 1 security associations.
-
clear crypto ipsec sa - (PIX) Clears the Phase 2 security associations.
-
clear crypto isakmp - (Router) Clears the Phase 1 security associations.
-
clear crypto sa - (Router) Clears the Phase 2 security associations.
Sample debug Output
Headquarters PIX Debugs
ISAKMP (0): beginning Main Mode exchange
IPSEC(ipsec_encap): crypto map check deny
02303: sa_request,
(key eng. msg.) src= 172.17.63.213, dest= 172.17.63.230,
src_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
dest_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 28800s and 4608000kb,
spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x4004
crypto_isakmp_process_block: src 172.17.63.230,
dest 172.17.63.213
OAK_MM exchange
ISAKMP (0): processing SA payload. message ID = 0
ISAKMP (0): Checking ISAKMP transform 1 against priority
21 policy
ISAKMP: encryption DES-CBC
ISAKMP: hash MD5
ISAKMP: default group 1
ISAKMP: auth pre-share
ISAKMP: life type in seconds
ISAKMP: life duration (basic) of 3600
ISAKMP (0): atts are acceptable. Next payload is 0
ISAKMP (0): SA is doing pre-shared key authentication
using id type ID_IPV4_ADDR
return status is IKMP_NO_ERRORIPSEC(ipsec_encap): crypto
map check deny
crypto_isakmp_process_block: src 172.17.63.230,
dest 172.17.63.213
OAK_MM exchange
ISAKMP (0): processing KE payload. message ID = 0
ISAKMP (0): processing NONCE payload. message ID = 0
ISAKMP (0): processing vendor id payload
ISAKMP (0): speaking to another IOS box!
ISAKMP (0): ID payload
next-payload : 8
type : 1
protocol : 17
port : 500
length : 8
ISAKMP (0): Total payload length: 12
return status is IKMP_NO_ERRORIPSEC(ipsec_encap):
crypto map check deny
crypto_isakmp_process_block: src 172.17.63.230,
dest 172.17.63.213
OAK_MM exchange
ISAKMP (0): processing ID payload. message ID = 0
ISAKMP (0): processing HASH payload. message ID = 0
ISAKMP (0): SA has been authenticated
ISAKMP (0): beginning Quick Mode exchange, M-ID of
-1448244754:a9ad89eeIPSEC(key_engine): got a
queue even
IPSEC(spi_response): getting spi 0x5cfcf6e9(1560082153)
for SA from 172.17.63.230 to
172.17.63.213 for prot 3
return status is IKMP_NO_ERROR
crypto_isakmp_process_block: src 172.17.63.230,
dest 172.17.63.213
OAK_QM exchange
oakley_process_quick_mode:
OAK_QM_IDLE
ISAKMP (0): processing SA payload. message ID =
-1448244754
ISAKMP : Checking IPSec proposal 1
ISAKMP: transform 1, ESP_DES
ISAKMP: attributes in transform:
ISAKMP: encaps is 1
ISAKMP: SA life type in seconds
ISAKMP: SA life duration (basic) of 28800
ISAKMP: SA life type in kilobytes
ISAKMP: SA life duration (VPI) of 0x0
0x46 0x50 0x0
ISAKMP: authenticator is HMAC-MD5
ISAKMP (0): atts are acceptable.IPSEC
(validate_proposal_request):
proposal part #1,
(key eng. msg.) dest= 172.17.63.230,
src= 172.17.63.213,
dest_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
src_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 0s and 0kb,
spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x4
ISAKMP (0): processing NONCE payload. message ID =
-1448244754
ISAKMP (0): processing ID payload. message ID =
-1448244754
ISAKMP (0): processing ID payload. message ID =
-1448244754
ISAKMP (0): processing NOTIFY payload 96 protocol 3
spi 1510339082, message ID = -1448244754
ISAKMP (0): processing responder lifetime
ISAKMP (0): responder lifetime of
3600sIPSEC(map_alloc_entry):
allocating entry 3
IPSEC(map_alloc_entry): allocating entry 4
ISAKMP (0): Creating IPSec SAs
inbound SA from 172.17.63.230 to
172.17.63.213
(proxy 10.2.2.0 to 10.1.1.0)
has spi 1560082153 and conn_id 3 and flags 4
lifetime of 3600 seconds
lifetime of 4608000 kilobytes
outbound SA from 172.17.63.213 to
172.17.63.230
(proxy 10.1.1.0 to 10.2.2.0)
has spi 183633242 and conn_id 4 and flags 4
lifetime of 3600 seconds
lifetime of 4608000 kilobytesIPSEC(key_engine):
got a queue event...
IPSEC(initialize_sas): ,
(key eng. msg.) dest= 172.17.63.213, src=
172.17.63.230,
dest_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
src_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 3600s and 4608000kb,
spi= 0x5cfcf6e9(1560082153), conn_id= 3, keysize= 0,
flags= 0x4
IPSEC(initialize_sas): ,
(key eng. msg.) src= 172.17.63.213, dest=
172.17.63.230,
src_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
dest_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 3600s and 4608000kb,
spi= 0xaf2055a(183633242), conn_id= 4, keysize= 0,
flags= 0x4
return status is IKMP_NO_ERROR602301: sa created,
(sa) sa_dest= 172.17.63.213, sa_prot= 50,
sa_spi= 0x5cfcf6e9(1560082153),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 3
602301: sa created,
(sa) sa_dest= 172.17.63.230, sa_prot= 50,
sa_spi= 0xaf2055a(183633242),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 4
Branch Router Debugs
Branch_Router#
01:27:08: ISAKMP (0): received packet from 172.17.63.213
(N) NEW SA
01:27:08: ISAKMP (0:1): processing SA payload.
message ID = 0
01:27:08: ISAKMP (0:1): Checking ISAKMP transform 1
against priority 11 policy
01:27:08: ISAKMP: encryption DES-CBC
01:27:08: ISAKMP: hash MD5
01:27:08: ISAKMP: default group 1
01:27:08: ISAKMP: auth pre-share
01:27:08: ISAKMP: life type in seconds
01:27:08: ISAKMP: life duration (basic) of 3600
01:27:08: ISAKMP (0:1): atts are acceptable. Next
payload is 0
01:27:08: CryptoEngine0: generate alg parameter
01:27:10: CRYPTO_ENGINE: Dh phase 1 status: 0
01:27:10: CRYPTO_ENGINE: Dh phase 1 status: 0
01:27:10: ISAKMP (0:1): SA is doing pre-shared key
authentication
01:27:10: ISAKMP (1): SA is doing pre-shared key
authentication using id type ID_IPV4_ADDR
01:27:10: ISAKMP (1): sending packet to 172.17.63.213
(R) MM_SA_SETUP
01:27:10: ISAKMP (1): received packet from 172.17.63.213
(R) MM_SA_SETUP
01:27:10: ISAKMP (0:1): processing KE payload. message
ID = 0
01:27:10: CryptoEngine0: generate alg parameter
01:27:12: ISAKMP (0:1): processing NONCE payload.
message ID = 0
01:27:12: CryptoEngine0: create ISAKMP SKEYID for
conn id 1
01:27:12: ISAKMP (0:1): SKEYID state generated
01:27:12: ISAKMP (0:1): processing vendor id payload
01:27:12: ISAKMP (0:1): speaking to another IOS box!
01:27:12: ISAKMP (1): sending packet to 172.17.63.213 (R)
MM_KEY_EXCH
01:27:12: ISAKMP (1): received packet from 172.17.63.213
(R) MM_KEY_EXCH
01:27:12: ISAKMP (0:1): processing ID payload.
message ID = 0
01:27:12: ISAKMP (0:1): processing HASH payload.
message ID = 0
01:27:12: CryptoEngine0: generate hmac context for
conn id 1
01:27:12: ISAKMP (0:1): SA has been authenticated
with 172.17.63.213
01:27:12: ISAKMP (1): ID payload
next-payload : 8
type : 1
protocol : 17
port : 500
length : 8
01:27:12: ISAKMP (1): Total payload length: 12
01:27:12: CryptoEngine0: generate hmac context
for conn id 1
01:27:12: CryptoEngine0: clear dh number for
conn id 1
01:27:12: ISAKMP (1): sending packet to
172.17.63.213 (R) QM_IDLE
01:27:12: ISAKMP (1): received packet from
172.17.63.213 (R) QM_IDLE
01:27:12: CryptoEngine0: generate hmac context for
conn id 1
01:27:12: ISAKMP (0:1): processing SA payload.
message ID = -1448244754
01:27:12: ISAKMP (0:1): Checking IPSec proposal 1
01:27:12: ISAKMP: transform 1, ESP_DES
01:27:12: ISAKMP: attributes in transform:
01:27:12: ISAKMP: encaps is 1
01:27:12: ISAKMP: SA life type in seconds
01:27:12: ISAKMP: SA life duration (basic)
of 28800
01:27:12: ISAKMP: SA life type in kilobytes
01:27:12: ISAKMP: SA life duration (VPI) of
0x0 0x46 0x50 0x0
01:27:12: ISAKMP: authenticator is HMAC-MD5
01:27:12: validate proposal 0
01:27:12: ISAKMP (0:1): atts are acceptable.
01:27:12: IPSEC(validate_proposal_request):
proposal part #1, (key eng. msg.)
dest= 172.17.63.230, src= 172.17.63.213,
dest_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
src_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 0s and 0kb,
spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x4
01:27:13: validate proposal request 0
01:27:13: ISAKMP (0:1): processing NONCE payload.
message ID = -1448244754
01:27:13: ISAKMP (0:1): processing ID payload.
message ID = -1448244754
01:27:13: ISAKMP (1): ID_IPV4_ADDR_SUBNET src
10.1.1.0/255.255.255.0 prot 0 port 0
01:27:13: ISAKMP (0:1): processing ID payload.
message ID = -1448244754
01:27:13: ISAKMP (1): ID_IPV4_ADDR_SUBNET dst
10.2.2.0/255.255.255.0 prot 0 port 0
01:27:13: IPSEC(key_engine): got a queue event...
01:27:13: IPSEC(spi_response): getting spi 183633242
for SA
from 172.17.63.213 to 172.17.63.230 for prot 3
01:27:13: CryptoEngine0: generate hmac context for
conn id 1
01:27:13: ISAKMP (1): sending packet to 172.17.63.213
(R) QM_IDLE
01:27:13: ISAKMP (1): received packet from 172.17.63.213
(R) QM_IDLE
01:27:13: CryptoEngine0: generate hmac context
for conn id 1
01:27:13: ipsec allocate flow 0
01:27:13: ipsec allocate flow 0
01:27:13: ISAKMP (0:1): Creating IPSec SAs
01:27:13: inbound SA from 172.17.63.213
to 172.17.63.230 (proxy 10.1.1.0 to 10.2.2.0)
01:27:13: has spi 183633242 and conn_id 2000
and flags 4
01:27:13: lifetime of 28800 seconds
01:27:13: lifetime of 4608000 kilobytes
01:27:13: outbound SA from 172.17.63.230
to 172.17.63.213 (proxy 10.2.2.0 to 10.1.1.0)
01:27:13: has spi 1560082153 and conn_id
2001 and flags 4
01:27:13: lifetime of 28800 seconds
01:27:13: lifetime of 4608000 kilobytes
01:27:13: ISAKMP (0:1): deleting node -1448244754
01:27:13: IPSEC(key_engine): got a queue event...
01:27:13: IPSEC(initialize_sas): ,
(key eng. msg.) dest= 172.17.63.230, src=
172.17.63.213,
dest_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
src_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 28800s and 4608000kb,
spi= 0xAF2055A(183633242), conn_id= 2000,
keysize= 0, flags= 0x4
01:27:13: IPSEC(initialize_sas): ,
(key eng. msg.) src= 172.17.63.230,
dest= 172.17.63.213,
src_proxy= 10.2.2.0/255.255.255.0/0/0 (type=4),
dest_proxy= 10.1.1.0/255.255.255.0/0/0 (type=4),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 28800s and 4608000kb,
spi= 0x5CFCF6E9(1560082153), conn_id= 2001,
keysize= 0, flags= 0x4
01:27:13: IPSEC(create_sa): sa created,
(sa) sa_dest= 172.17.63.230, sa_prot= 50,
sa_spi= 0xAF2055A(183633242),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 2000
01:27:13: IPSEC(create_sa): sa created,
(sa) sa_dest= 172.17.63.213, sa_prot= 50,
sa_spi= 0x5CFCF6E9(1560082153),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 2001
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