Router a tre interfacce senza configurazione NAT Cisco IOS Firewall

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Aggiornato:20 febbraio 2007

ID documento:13893

Linguaggio senza pregiudizi

La documentazione per questo prodotto è stata redatta cercando di utilizzare un linguaggio senza pregiudizi. Ai fini di questa documentazione, per linguaggio senza di pregiudizi si intende un linguaggio che non implica discriminazioni basate su età, disabilità, genere, identità razziale, identità etnica, orientamento sessuale, status socioeconomico e intersezionalità. Le eventuali eccezioni possono dipendere dal linguaggio codificato nelle interfacce utente del software del prodotto, dal linguaggio utilizzato nella documentazione RFP o dal linguaggio utilizzato in prodotti di terze parti a cui si fa riferimento. Scopri di più sul modo in cui Cisco utilizza il linguaggio inclusivo.

Informazioni su questa traduzione

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Sommario

Introduzione

Prerequisiti

Requisiti

Componenti usati

Convenzioni

Configurazione

Esempio di rete

Configurazioni

Verifica

Risoluzione dei problemi

Informazioni correlate

Introduzione

In questo documento viene illustrato un esempio di configurazione tipica per una piccola azienda connessa a Internet che esegue i propri server. La connessione a Internet avviene tramite una linea seriale. Ethernet 0 è collegato alla rete interna (una singola LAN). Ethernet 1 è collegato a una rete DMZ, che ha un singolo nodo utilizzato per fornire servizi al mondo esterno. L'ISP ha assegnato alla società il netblock 192.168.27.0/24. Tale subnet mask è suddivisa in due parti: la DMZ e la LAN interna con subnet mask 255.255.255.128. La policy di base prevede quanto segue:

Consente agli utenti della rete interna di connettersi a qualsiasi servizio della rete Internet pubblica.
Consentire a tutti gli utenti di Internet di connettersi ai servizi WWW, FTP e SMTP (Simple Mail Transfer Protocol) nel server DMZ e di eseguire query DNS (Domain Name System) in tale server. Questo consente agli utenti esterni di visualizzare le pagine Web della società, prelevare i file inviati dalla società per l'utilizzo esterno e inviare messaggi alla società.
Consentire agli utenti interni di connettersi al servizio POP sul server DMZ (per ritirare la posta) e di connettersi in modalità Telnet (per amministrarla).
Non consentire a nessun utente della zona demilitarizzata di avviare connessioni, né alla rete privata né a Internet.
Controllare tutte le connessioni che attraversano il firewall per raggiungere un server SYSLOG nella rete privata. I computer nella rete interna utilizzano il server DNS nella DMZ. Gli elenchi degli accessi agli input vengono usati su tutte le interfacce per impedire lo spoofing. Gli elenchi degli accessi di output vengono utilizzati per controllare il traffico che può essere inviato a una determinata interfaccia.

Per configurare un router a due interfacce senza NAT con Cisco IOS Firewall, consultare il documento sulla configurazione del firewall a due interfacce senza NAT con Cisco IOS® Firewall.

Per configurare un router a due interfacce con NAT usando un Cisco IOS Firewall, consultare il documento sulla configurazione del firewall a due interfacce con NAT.

Prerequisiti

Requisiti

Nessun requisito specifico previsto per questo documento.

Componenti usati

Le informazioni fornite in questo documento si basano sulle versioni software e hardware:

Software Cisco IOS release 12.2(15)T13 con set di funzionalità firewall
Router Cisco 7204 VXR

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.

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 viene usata questa configurazione.

Router 7204 VXR
version 12.2 service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname Router ! logging queue-limit 100 enable secret 5 <something> ! ip subnet-zero ip cef no ip domain lookup ! ip inspect audit-trail ! !--- Sets the length of time a TCP session !--- is still managed after no activity. ! ip inspect tcp idle-time 14400 ! !--- Sets the length of time a UDP session !--- is still managed after no activity. ! ip inspect udp idle-time 1800 ! !--- Sets the length of time a DNS name lookup session !--- is still managed after no activity. ! ip inspect dns-timeout 7 ! !--- Sets up inspection list "standard" !--- to be used for inspection of inbound Ethernet 0 !--- and inbound serial (applied to both interfaces). ! ip inspect name standard cuseeme ip inspect name standard ftp ip inspect name standard h323 ip inspect name standard http ip inspect name standard rcmd ip inspect name standard realaudio ip inspect name standard smtp ip inspect name standard sqlnet ip inspect name standard streamworks ip inspect name standard tcp ip inspect name standard tftp ip inspect name standard udp ip inspect name standard vdolive ip audit notify log ip audit po max-events 100 ! no voice hpi capture buffer no voice hpi capture destination ! mta receive maximum-recipients 0 ! interface ethernet 3/0 ip address 192.168.27.129 255.255.255.128 ! !--- Apply the access list to allow all legitimate !--- traffic from the inside network and prevent spoofing. ! ip access-group 101 in ! !--- Apply inspection list "standard" for inspection !--- of inbound Ethernet traffic. This inspection opens !--- temporary entries on access lists 111 and 121. ! ip inspect standard in duplex full interface ethernet 3/1 ip address 192.168.27.1 255.255.255.128 ! !--- Apply the access list to permit DMZ traffic (except spoofing) !--- on the DMZ interface inbound. The DMZ is not permitted to initiate !--- any outbound traffic except Internet Control Message Protocol (ICMP). ! ip access-group 111 in ! !--- Apply inspection list "standard" for inspection of outbound !--- traffic from e1. This adds temporary entries on access list 111 !--- to allow return traffic, and protects servers in DMZ from !--- distributed denial of service (DDoS) attacks. ip inspect standard out duplex full ! interface serial 2/0 ip address 10.89.129.194 255.255.255.252 !--- Apply the access list to allow legitimate traffic. ! ip access-group 121 in serial restart_delay 0 ! ip classless no ip http-server !--- A syslog server is located at this address. logging 192.168.27.131 !--- This command enables the logging of session !--- information (addresses and bytes). !--- Access list 20 is used to control which !--- network management stations can access via SNMP. ! access-list 20 permit 192.168.27.5 ! !--- Use an access list to allow all legitimate traffic from !--- the inside network and prevent spoofing. The inside !--- network can only connect to the Telnet and POP3 !--- service of 192.168.27.3 on DMZ, and can ping (ICMP) to the DMZ. !--- Additional entries can be added to permit SMTP, WWW, and !--- so forth, if necessary. In addition, the inside network can !--- connect to any service on the Internet. ! access-list 101 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq pop3 access-list 101 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq telnet access-list 101 permit icmp 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127 access-list 101 deny ip 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127 access-list 101 permit ip 192.168.27.128 0.0.0.127 any access-list 101 deny ip any any ! ! !--- The access list permits ping (ICMP) from the DMZ and denies all !--- traffic initiated from the DMZ. Inspection opens !--- temporary entries to this list. ! access-list 111 permit icmp 192.168.27.0 0.0.0.127 any access-list 111 deny ip any any ! ! ! !--- Access list 121 allows anyone on the Internet to connect to !--- WWW, FTP, DNS, and SMTP services on the DMZ host. It also !--- allows some ICMP traffic. access-list 121 permit udp any host 192.168.27.3 eq domain access-list 121 permit tcp any host 192.168.27.3 eq domain access-list 121 permit tcp any host 192.168.27.3 eq www access-list 121 permit tcp any host 192.168.27.3 eq ftp access-list 121 permit tcp any host 192.168.27.3 eq smtp access-list 121 permit icmp any 192.168.27.0 0.0.0.255 administratively-prohibited access-list 121 permit icmp any 192.168.27.0 0.0.0.255 echo access-list 121 permit icmp any 192.168.27.0 0.0.0.255 echo-reply access-list 121 permit icmp any 192.168.27.0 0.0.0.255 packet-too-big access-list 121 permit icmp any 192.169.27.0 0.0.0.255 time-exceeded access-list 121 permit icmp any 192.168.27.0 0.0.0.255 traceroute access-list 121 permit icmp any 192.168.27.0 0.0.0.255 unreachable access-list 121 deny ip any any ! !--- Apply access list 20 for SNMP process. ! snmp-server community secret RO 20 snmp-server enable traps tty ! call rsvp-sync ! mgcp profile default ! dial-peer cor custom ! gatekeeper shutdown ! line con 0 exec-timeout 5 0 password 7 14191D1815023F2036 login local line vty 0 4 exec-timeout 5 0 password 7 14191D1815023F2036 login local length 35 end

Router 7204 VXR

version 12.2
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname Router
!
logging queue-limit 100
enable secret 5 <something>
!
ip subnet-zero
ip cef
no ip domain lookup
!
ip inspect audit-trail
!

!--- Sets the length of time a TCP session !--- is still managed after no activity.

!
ip inspect tcp idle-time 14400
!

!--- Sets the length of time a UDP session !--- is still managed after no activity.

!
ip inspect udp idle-time 1800
!

!--- Sets the length of time a DNS name lookup session !--- is still managed after no activity.

!
ip inspect dns-timeout 7
!

!--- Sets up inspection list "standard" !--- to be used for inspection of inbound Ethernet 0 !--- and inbound serial (applied to both interfaces).

!
ip inspect name standard cuseeme
ip inspect name standard ftp
ip inspect name standard h323
ip inspect name standard http
ip inspect name standard rcmd
ip inspect name standard realaudio
ip inspect name standard smtp
ip inspect name standard sqlnet
ip inspect name standard streamworks
ip inspect name standard tcp
ip inspect name standard tftp
ip inspect name standard udp
ip inspect name standard vdolive
ip audit notify log
ip audit po max-events 100
!
no voice hpi capture buffer
no voice hpi capture destination
!
mta receive maximum-recipients 0
!

interface ethernet 3/0
ip address 192.168.27.129 255.255.255.128
!

!--- Apply the access list to allow all legitimate !--- traffic from the inside network and prevent spoofing.

!
ip access-group 101 in
!

!--- Apply inspection list "standard" for inspection !--- of inbound Ethernet traffic. This inspection opens !--- temporary entries on access lists 111 and 121.

!
ip inspect standard in
duplex full

interface ethernet 3/1
ip address 192.168.27.1 255.255.255.128

!--- Apply the access list to permit DMZ traffic (except spoofing) !--- on the DMZ interface inbound. The DMZ is not permitted to initiate !--- any outbound traffic except Internet Control Message Protocol (ICMP).

!
ip access-group 111 in
!

!--- Apply inspection list "standard" for inspection of outbound !--- traffic from e1. This adds temporary entries on access list 111 !--- to allow return traffic, and protects servers in DMZ from !--- distributed denial of service (DDoS) attacks.

ip inspect standard out
duplex full
!
interface serial 2/0
ip address 10.89.129.194 255.255.255.252

!--- Apply the access list to allow legitimate traffic.

!
ip access-group 121 in
serial restart_delay 0
!
ip classless
no ip http-server

!--- A syslog server is located at this address.

logging 192.168.27.131

!--- This command enables the logging of session !--- information (addresses and bytes). !--- Access list 20 is used to control which !--- network management stations can access via SNMP.

!
access-list 20 permit 192.168.27.5
!

!--- Use an access list to allow all legitimate traffic from !--- the inside network and prevent spoofing. The inside !--- network can only connect to the Telnet and POP3 !--- service of 192.168.27.3 on DMZ, and can ping (ICMP) to the DMZ. !--- Additional entries can be added to permit SMTP, WWW, and !--- so forth, if necessary. In addition, the inside network can !--- connect to any service on the Internet.

!
access-list 101 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq pop3
access-list 101 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq telnet
access-list 101 permit icmp 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127
access-list 101 deny ip 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127
access-list 101 permit ip 192.168.27.128 0.0.0.127 any
access-list 101 deny ip any any
!
!

!--- The access list permits ping (ICMP) from the DMZ and denies all !--- traffic initiated from the DMZ. Inspection opens !--- temporary entries to this list.

!
access-list 111 permit icmp 192.168.27.0 0.0.0.127 any
access-list 111 deny ip any any
!
!
!

!--- Access list 121 allows anyone on the Internet to connect to !--- WWW, FTP, DNS, and SMTP services on the DMZ host. It also !--- allows some ICMP traffic.

access-list 121 permit udp any host 192.168.27.3 eq domain
access-list 121 permit tcp any host 192.168.27.3 eq domain
access-list 121 permit tcp any host 192.168.27.3 eq www
access-list 121 permit tcp any host 192.168.27.3 eq ftp
access-list 121 permit tcp any host 192.168.27.3 eq smtp
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 administratively-prohibited
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 echo
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 echo-reply
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 packet-too-big
access-list 121 permit icmp any 192.169.27.0 0.0.0.255 time-exceeded
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 traceroute
access-list 121 permit icmp any 192.168.27.0 0.0.0.255 unreachable
access-list 121 deny ip any any

!--- Apply access list 20 for SNMP process.

!
snmp-server community secret RO 20
snmp-server enable traps tty
!
call rsvp-sync
!
mgcp profile default
!
dial-peer cor custom
!
gatekeeper shutdown
!

line con 0
exec-timeout 5 0
password 7 14191D1815023F2036
login local
line vty 0 4
exec-timeout 5 0
password 7 14191D1815023F2036
login local
length 35
end

Verifica

Per verificare che la configurazione funzioni correttamente, consultare questa sezione.

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 access-list: verifica la configurazione corretta degli elenchi degli accessi configurati nella configurazione corrente.

Router#show access-list
Standard IP access list 20
       10 permit 192.168.27.5
Extended IP access list 101
       10 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq pop3
       20 permit tcp 192.168.27.128 0.0.0.127 host 192.168.27.3 eq telnet
       30 permit icmp 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127
       40 deny ip 192.168.27.128 0.0.0.127 192.168.27.0 0.0.0.127
       50 permit ip 192.168.27.128 0.0.0.127 any
       60 deny ip any any
Extended IP access list 111
       10 permit icmp 192.168.27.0 0.0.0.127 any
       20 deny ip any any (9 matches)
Extended IP access list 121
       10 permit udp any host 192.168.27.3 eq domain
       20 permit tcp any host 192.168.27.3 eq domain
       30 permit tcp any host 192.168.27.3 eq www
       40 permit tcp any host 192.168.27.3 eq ftp
       50 permit tcp any host 192.168.27.3 eq smtp
       60 permit icmp any 192.168.27.0 0.0.0.255 administratively-prohibited
       70 permit icmp any 192.168.27.0 0.0.0.255 echo
       80 permit icmp any 192.168.27.0 0.0.0.255 echo-reply
       90 permit icmp any 192.168.27.0 0.0.0.255 packet-too-big
       100 permit icmp any 192.169.27.0 0.0.0.255 time-exceeded
       110 permit icmp any 192.168.27.0 0.0.0.255 traceroute
       120 permit icmp any 192.168.27.0 0.0.0.255 unreachable
       130 deny ip any any (4866 matches)
Router#

show ip audit all: verifica la configurazione dei comandi di log.

Router#show ip audit all
Event notification through syslog is enabled
Event notification through Net Director is disabled
Default action(s) for info signatures is alarm
Default action(s) for attack signatures is alarm
Default threshold of recipients for spam signature is 250
PostOffice:HostID:0 OrgID:0 Msg dropped:0
          :Curr Event Buf Size:0 Configured:100
Post Office is not enabled - No connections are active

Router#

show ip inspect all: verifica la configurazione delle regole di ispezione del firewall Cisco IOS per interfaccia.

Router#show ip inspect all
    Session audit trail is enabled
    Session alert is enabled
    one-minute (sampling period) thresholds are [400:500] connections
    max-incomplete sessions thresholds are [400:500]
    max-incomplete tcp connections per host is 50. Block-time 0 minute.
    tcp synwait-time is 30 sec -- tcp finwait-time is 5 sec
    tcp idle-time is 14400 sec -- udp idle-time is 1800 sec
    dns-timeout is 7 sec
    Inspection Rule Configuration
     Inspection name standard
       cuseeme alert is on audit-trail is on timeout 14400
       ftp alert is on audit-trail is on timeout 14400
       h323 alert is on audit-trail is on timeout 14400
       http alert is on audit-trail is on timeout 14400
       rcmd alert is on audit-trail is on timeout 14400
       realaudio alert is on audit-trail is on timeout 14400
       smtp alert is on audit-trail is on timeout 14400
       sqlnet alert is on audit-trail is on timeout 14400
       streamworks alert is on audit-trail is on timeout 1800
       tcp alert is on audit-trail is on timeout 14400
       tftp alert is on audit-trail is on timeout 1800
       udp alert is on audit-trail is on timeout 1800
       vdolive alert is on audit-trail is on timeout 14400       
Interface Configuration
     Interface Ethernet3/0
       Inbound inspection rule is standard
         cuseeme alert is on audit-trail is on timeout 14400
         ftp alert is on audit-trail is on timeout 14400
         h323 alert is on audit-trail is on timeout 14400
         http alert is on audit-trail is on timeout 14400
         rcmd alert is on audit-trail is on timeout 14400
         realaudio alert is on audit-trail is on timeout 14400
         smtp alert is on audit-trail is on timeout 14400
         sqlnet alert is on audit-trail is on timeout 14400
         streamworks alert is on audit-trail is on timeout 1800
         tcp alert is on audit-trail is on timeout 14400
         tftp alert is on audit-trail is on timeout 1800
         udp alert is on audit-trail is on timeout 1800
         vdolive alert is on audit-trail is on timeout 14400
       Outgoing inspection rule is not set
       Inbound access list is 101
       Outgoing access list is not set
     Interface Ethernet3/1
       Inbound inspection rule is not set
       Outgoing inspection rule is standard
         cuseeme alert is on audit-trail is on timeout 14400
         ftp alert is on audit-trail is on timeout 14400
         h323 alert is on audit-trail is on timeout 14400
         http alert is on audit-trail is on timeout 14400
         rcmd alert is on audit-trail is on timeout 14400
         realaudio alert is on audit-trail is on timeout 14400
         smtp alert is on audit-trail is on timeout 14400
         sqlnet alert is on audit-trail is on timeout 14400
         streamworks alert is on audit-trail is on timeout 1800
         tcp alert is on audit-trail is on timeout 14400
         tftp alert is on audit-trail is on timeout 1800
         udp alert is on audit-trail is on timeout 1800
         vdolive alert is on audit-trail is on timeout 14400
       Inbound access list is 111
       Outgoing access list is not set
Router#

Risoluzione dei problemi

Dopo aver configurato il router del firewall IOS, se le connessioni non funzionano, verificare di aver abilitato l'ispezione con il comando ip inspect (nome definito) sull'interfaccia in o out. in questa configurazione, lo standard ip inspect in viene applicato all'interfaccia ethernet 3/0 e l'uscita standard ip inspect viene applicata all'interfaccia ethernet 3/1.

Per ulteriori informazioni sulla risoluzione dei problemi, fare riferimento a Risoluzione dei problemi di configurazione di Cisco IOS Firewall.

Informazioni correlate

Cronologia delle revisioni

Revisione	Data di pubblicazione	Commenti
1.0	20-Feb-2007	Versione iniziale

Router a tre interfacce senza configurazione NAT Cisco IOS Firewall

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