PIX/ASA 7.x e versioni successive: Esempio di configurazione della VPN IPsec da LAN a LAN con reti sovrapposte

Introduzione

In questo documento viene descritta la procedura utilizzata per tradurre (NAT) il traffico VPN che attraversa un tunnel IPsec da LAN a LAN (L2L) tra due appliance di sicurezza e il traffico Internet. Ogni appliance di sicurezza dispone di una rete privata protetta. Nell'esempio, due appliance Cisco Adaptive Security (ASA) con reti interne identiche e sovrapposte sono collegate sul tunnel VPN. In uno scenario normale, la comunicazione sulla VPN non avviene mai perché i pacchetti ping non lasciano mai la subnet locale poiché l'utente esegue il ping dell'indirizzo IP della stessa subnet. Affinché le due reti interne private comunichino tra loro, la policy NAT viene utilizzata su entrambe le appliance ASA per la traduzione della subnet locale in modo che la comunicazione avvenga come previsto.

Prerequisiti

Requisiti

Prima di procedere con questo esempio di configurazione, verificare di aver configurato Cisco Adaptive Security Appliance con gli indirizzi IP sulle interfacce e di disporre della connettività di base.

Componenti usati

Le informazioni di questo documento si basano sulla seguente versione del software:

• Software Cisco Adaptive Security Appliance versione 7.x e successive.

Le informazioni discusse in questo documento fanno riferimento a dispositivi usati in uno specifico ambiente di emulazione. Su tutti i dispositivi menzionati nel documento la configurazione è stata ripristinata ai valori predefiniti. Se la rete è operativa, valutare attentamente eventuali conseguenze derivanti dall'uso dei comandi.

Prodotti correlati

Questa configurazione può essere utilizzata anche con Cisco PIX Security Appliance versione 7.x e successive.

Convenzioni

Fare riferimento a Cisco Technical Tips Conventions per ulteriori informazioni sulle convenzioni dei documenti.

Configurazione

In questa sezione vengono presentate le informazioni necessarie per configurare le funzionalità descritte più avanti nel documento.

Nota: per ulteriori informazioni sui comandi menzionati in questa sezione, usare lo strumento di ricerca dei comandi (solo utenti registrati).

Esempio di rete

Nel documento viene usata questa impostazione di rete:

Configurazioni

Nel documento vengono usate queste configurazioni:

• Configurazione ASA-1

• Configurazione ASA-2

ASA-1#show running-config 
: Saved
:
ASA Version 8.0(3)
!
hostname ciscoasa
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
 nameif outside
 security-level 0
 ip address 172.162.1.1 255.255.255.0

!--- Configure the outside interface.

!

interface Ethernet1
 nameif inside
 security-level 100
 ip address 192.168.1.1 255.255.255.0

!--- Configure the inside interface.


passwd 2KFQnbNIdI.2KYOU encrypted                                                      
ftp mode passive


access-list new extended permit ip 192.168.2.0 255.255.255.0 192.168.3.0 255.255.255.0

!--- This access list (new) is used with the crypto map (outside_map) !--- in order to determine which traffic should be encrypted !--- and sent across the tunnel.



access-list policy-nat extended permit ip 192.168.1.0 255.255.255.0 192.168.3.0 255.255.255.0


!--- The policy-nat ACL is used with the static !--- command in order to match the VPN traffic for translation. 

pager lines 24
mtu outside 1500
mtu inside 1500
no failover
asdm image flash:/asdm-615.bin
no asdm history enable
arp timeout 14400


static (inside,outside) 192.168.2.0  access-list policy-nat

!--- It is a Policy NAT statement. !--- The static command with the access list (policy-nat), !--- which matches the VPN traffic and translates the source (192.168.1.0) to !--- 192.168.2.0 for outbound VPN traffic.


global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0

!--- The previous statements PAT the Internet traffic !--- except for the VPN traffic that uses the IP address 172.17.1.1. 

route outside 0.0.0.0 0.0.0.0 172.162.1.2 1



!--- Output is suppressed.



!--- PHASE 2 CONFIGURATION ---! !--- The encryption types for Phase 2 are defined here.


crypto ipsec transform-set CISCO esp-des esp-md5-hmac

!--- Define the transform set for Phase 2.

crypto map outside_map 20 match address new

!--- Define which traffic should be sent to the IPsec peer with the !--- access list (new). 

crypto map outside_map 20 set peer 172.162.1.2

!--- Sets the IPsec peer (remote end point)


crypto map outside_map 20 set transform-set CISCO

!--- Sets the IPsec transform set "CISCO" !--- to be used with the crypto map entry "outside_map"

crypto map outside_map interface outside

!--- Specifies the interface to be used with !--- the settings defined in this configuration !--- PHASE 1 CONFIGURATION ---! !--- This configuration uses isakmp policy 65535. !--- Policy 65535 is included in the configuration by default. !--- These configuration commands define the !--- Phase 1 policy parameters that are used.

crypto isakmp identity address
crypto isakmp enable outside
crypto isakmp policy 65535
 authentication pre-share
 encryption des
 hash md5
 group 2
 lifetime 86400

tunnel-group 172.162.1.2 type ipsec-l2l

!--- In order to create and manage the database of connection-specific records !--- for IPsec-L2L—IPsec (LAN-to-LAN) tunnels, use the tunnel-group !--- command in global configuration mode. !--- For L2L connections, the name of the tunnel group must be !--- the IP address of the IPsec peer (remote peer end).

tunnel-group 172.162.1.2 ipsec-attributes
 pre-shared-key *

!--- Enter the pre-shared key in order to configure the authentication method. 


telnet timeout 5
ssh timeout 5
console timeout 0
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map global_policy
 class inspection_default
  inspect dns maximum-length 512
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect rtsp
  inspect skinny
  inspect esmtp
  inspect sqlnet
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp
!
service-policy global_policy global
Cryptochecksum:33e1e37cd1280d908210dac0cc26e706
: end

ASA-2#show running-config 
: Saved
:
ASA Version 8.0(3)
!
hostname ASA-2
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
 nameif outside
 security-level 0
 ip address 172.162.1.2 255.255.255.0                                                
!
interface Ethernet1
 nameif inside
 security-level 100
 ip address 192.168.1.1 255.255.255.0
!

!--- Output is suppressed.


access-list new extended permit ip 192.168.3.0 255.255.255.0 192.168.2.0 255.255.255.0

!--- This access list (new) is used with the crypto map (outside_map) !--- in order to determine which traffic needs to be encrypted !--- and sent across the tunnel.



access-list policy-nat extended permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0


!--- The policy-nat ACL is used with the static !--- command in order to match the VPN traffic for translation. 

pager lines 24
mtu outside 1500
mtu inside 1500
no failover
asdm image flash:/asdm-615.bin
no asdm history enable
arp timeout 14400



static (inside,outside) 192.168.3.0  access-list policy-nat

!--- This is a Policy NAT statement. !--- The static command with the access list (policy-nat), !--- which matches the VPN traffic and translates the source (192.168.1.0) to !--- 192.168.3.0 for outbound VPN traffic.

global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0

!--- The previous statements PAT the Internet traffic !--- except the VPN traffic that uses the outside interface IP address. 



 
route outside 0.0.0.0 0.0.0.0 172.162.1.2 1

!--- PHASE 2 CONFIGURATION ---! !--- The encryption types for Phase 2 are defined here.


crypto ipsec transform-set CISCO esp-des esp-md5-hmac

!--- Define the transform set for Phase 2.



crypto map outside_map 20 match address new

!--- Define which traffic needs to be sent to the IPsec peer.


crypto map outside_map 20 set peer 172.162.1.1

!--- Sets the IPsec peer.


crypto map outside_map 20 set transform-set CISCO

!--- Sets the IPsec transform set "CISCO" !--- to be used with the crypto map entry "outside_map".


crypto map outside_map interface outside

 !--- Specifies the interface to be used with !--- the settings defined in this configuration. !--- PHASE 1 CONFIGURATION ---! !--- This configuration uses isakmp policy 65535 !--- which is included in the configuration by default. !--- The configuration commands here define the !--- Phase 1 policy parameters that are used.



crypto isakmp identity address
crypto isakmp enable outside
crypto isakmp policy 65535
 authentication pre-share
 encryption des
 hash md5
 group 2
 lifetime 86400


!--- Output is suppressed.



!--- In order to create and manage the database of connection-specific !--- records for IPsec-L2L—IPsec (LAN-to-LAN) tunnels, use the !--- tunnel-group  command in global configuration mode. !--- For L2L connections, the name of the tunnel group must be !--- the IP address of the IPsec peer.


tunnel-group 172.162.1.1 type ipsec-l2l
tunnel-group 172.162.1.1 ipsec-attributes
 pre-shared-key *

!--- Enter the pre-shared key in order to configure the authentication method. 


prompt hostname context
Cryptochecksum:6b505b4a05c1aee96a71e67c23e71865
: end

Verifica

Fare riferimento a questa sezione per verificare che la configurazione funzioni correttamente.

Lo strumento Output Interpreter (solo utenti registrati) (OIT) supporta alcuni comandi show. Usare l'OIT per visualizzare un'analisi dell'output del comando show:

• show crypto isakmp sa: visualizza tutte le associazioni di sicurezza IKE correnti in un peer.

• show crypto ipsec sa: visualizza le impostazioni utilizzate dalle associazioni di protezione correnti.

show Commands da ASA-1

ASA-1#show crypto isakmp sa

   

Active SA: 1
    Rekey SA: 0 (A tunnel will report 1 Active and 1 Rekey SA during rekey)
Total IKE SA: 1

1   IKE Peer: 172.162.1.2
    Type    : L2L             Role    : initiator
    Rekey   : no              State   : MM_ACTIVE

ASA-1#show crypto ipsec sa
interface: outside
    Crypto map tag: outside_map, seq num: 20, local addr: 172.162.1.1

      access-list new permit ip 192.168.2.0 255.255.255.0 192.168.3.0 

255.255.2
5.0
      local ident (addr/mask/prot/port): (192.168.2.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (192.168.3.0/255.255.255.0/0/0)
      current_peer: 172.162.1.2

      #pkts encaps: 9, #pkts encrypt: 9, #pkts digest: 9
      #pkts decaps: 9, #pkts decrypt: 9, #pkts verify: 9
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 9, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #send errors: 0, #recv errors: 0

      local crypto endpt.: 172.162.1.1, remote crypto endpt.: 172.162.1.2

      path mtu 1500, ipsec overhead 58, media mtu 1500
      current outbound spi: 0BA6CD7E

    inbound esp sas:
      spi: 0xFB4BD01A (4216049690)
         transform: esp-des esp-md5-hmac none
         in use settings ={L2L, Tunnel, }
         slot: 0, conn_id: 8192, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (3824999/27738)
         IV size: 8 bytes
         replay detection support: Y
    outbound esp sas:
      spi: 0x0BA6CD7E (195480958)
         transform: esp-des esp-md5-hmac none
         in use settings ={L2L, Tunnel, }
         slot: 0, conn_id: 8192, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (3824999/27738)
         IV size: 8 bytes
         replay detection support: Y

ASA-1#show nat


NAT policies on Interface inside:
  match ip inside 192.168.1.0 255.255.255.0 outside 192.168.3.0 255.255.255.0
    static translation to 192.168.2.0
    translate_hits = 12, untranslate_hits = 5
  match ip inside any outside any
    dynamic translation to pool 1 (172.162.1.1 [Interface PAT])
    translate_hits = 0, untranslate_hits = 0
  match ip inside any inside any
    dynamic translation to pool 1 (No matching global)
    translate_hits = 0, untranslate_hits = 0
  match ip inside any dmz any
    dynamic translation to pool 1 (No matching global)
    translate_hits = 0, untranslate_hits = 0

ASA-1#show xlate

1 in use, 1 most used
Global 192.168.2.0 Local 192.168.1.0

show Commands da ASA-2

ASA-2#show crypto ipsec sa

interface: outside
    Crypto map tag: outside_map, seq num: 20, local addr: 172.162.1.2

      access-list new permit ip 192.168.3.0 255.255.255.0 192.168.2.0 

255.255.25
5.0
      local ident (addr/mask/prot/port): (192.168.3.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (192.168.2.0/255.255.255.0/0/0)
      current_peer: 172.162.1.1

      #pkts encaps: 9, #pkts encrypt: 9, #pkts digest: 9
      #pkts decaps: 9, #pkts decrypt: 9, #pkts verify: 9
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 9, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #send errors: 0, #recv errors: 0

      local crypto endpt.: 172.162.1.2, remote crypto endpt.: 172.162.1.1

      path mtu 1500, ipsec overhead 58, media mtu 1500
      current outbound spi: FB4BD01A

    inbound esp sas:
      spi: 0x0BA6CD7E (195480958)
         transform: esp-des esp-md5-hmac none
         in use settings ={L2L, Tunnel, }
         slot: 0, conn_id: 8192, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (4274999/26902)
         IV size: 8 bytes
         replay detection support: Y
    outbound esp sas:
      spi: 0xFB4BD01A (4216049690)
         transform: esp-des esp-md5-hmac none
         in use settings ={L2L, Tunnel, }
         slot: 0, conn_id: 8192, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (4274999/26902)
         IV size: 8 bytes
         replay detection support: Y

ASA-2#show crypto isakmp sa

Active SA: 1
    Rekey SA: 0 (A tunnel will report 1 Active and 1 Rekey SA during rekey)
Total IKE SA: 1

1   IKE Peer: 172.162.1.1
    Type    : L2L             Role    : responder
    Rekey   : no              State   : MM_ACTIVE

Risoluzione dei problemi

Cancella associazioni di protezione

Quando si esegue la risoluzione dei problemi, assicurarsi di cancellare le associazioni di protezione esistenti dopo aver apportato una modifica. In modalità privilegiata di PIX, utilizzare i seguenti comandi:

• clear crypto ipsec sa: elimina le SA IPsec attive.

• clear crypto isakmp sa: elimina le associazioni di protezione IKE attive.

Comandi per la risoluzione dei problemi

Lo strumento Output Interpreter (solo utenti registrati) supporta alcuni comandi show. Usare l'OIT per visualizzare un'analisi dell'output del comando show.

Nota: consultare le informazioni importanti sui comandi di debug prima di usare i comandi di debug.

• debug crypto ipsec: visualizza le negoziazioni IPsec della fase 2.

• debug crypto isakmp: visualizza le negoziazioni ISAKMP della fase 1.

Informazioni correlate

• Soluzioni per la risoluzione dei problemi più comuni di VPN IPsec L2L e ad accesso remoto
• PIX 7.0 e Adaptive Security Appliance Port Redirection(Forwarding) con comandi nat, global, static, conduit e access-list
• PIX/ASA 7.x e FWSM: Dichiarazioni NAT e PAT
• Cisco ASA serie 5500 Security Appliance
• Cisco PIX serie 500 Security Appliance
• Negoziazione IPSec/protocolli IKE
• Documentazione e supporto tecnico – Cisco Systems