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Cisco ASA Series CLI Configuration Guide
Chapter 1 Information About NAT
DNS and NAT
! Use twice NAT to pass traffic between the inside network and the VPN client without
! address translation (identity NAT), w/route-lookup:
nat (outside,inside) source static vpn_local vpn_local destination static inside_nw
inside_nw route-lookup
Troubleshooting NAT and VPN
See the following monitoring tools for troubleshooting NAT issues with VPN:
•
Packet tracer—When used correctly, a packet tracer shows which NAT rules a packet is hitting.
•
show nat detail
—Shows hit counts and untranslated traffic for a given NAT rule.
•
show conn all
—Lets you see active connections including to and from the box traffic.
To familiarize yourself with a non-working configuration vs. a working configuration, you can perform
the following steps:
1.
Configure VPN without identity NAT.
2.
Enter
show nat detail
and
show conn all
.
3.
Add the identity NAT configuration.
•
Repeat
show nat detail
and
show conn all
.
DNS and NAT
You might need to configure the ASA to modify DNS replies by replacing the address in the reply with
an address that matches the NAT configuration. You can configure DNS modification when you
configure each translation rule.
This feature rewrites the address in DNS queries and replies that match a NAT rule (for example, the A
record for IPv4, the AAAA record for IPv6, or the PTR record for reverse DNS queries). For DNS replies
traversing from a mapped interface to any other interface, the record is rewritten from the mapped value
to the real value. Inversely, for DNS replies traversing from any interface to a mapped interface, the
record is rewritten from the real value to the mapped value.
Note
If you configure a twice NAT rule, you cannot configure DNS modification if you specify the source
address as well as the destination address. These kinds of rules can potentially have a different
translation for a single address when going to A vs. B. Therefore, the ASA cannot accurately match the
IP address inside the DNS reply to the correct twice NAT rule; the DNS reply does not contain
information about which source/destination address combination was in the packet that prompted the
DNS request.
shows a DNS server that is accessible from the outside interface. A server, ftp.cisco.com, is
on the inside interface. You configure the ASA to statically translate the ftp.cisco.com real address
(10.1.3.14) to a mapped address (209.165.201.10) that is visible on the outside network. In this case, you
want to enable DNS reply modification on this static rule so that inside users who have access to
ftp.cisco.com using the real address receive the real address from the DNS server, and not the mapped
address. When an inside host sends a DNS request for the address of ftp.cisco.com, the DNS server
replies with the mapped address (209.165.201.10). The ASA refers to the static rule for the inside server
Содержание 5505 - ASA Firewall Edition Bundle
Страница 28: ...Glossary GL 24 Cisco ASA Series CLI Configuration Guide ...
Страница 61: ...P A R T 1 Getting Started with the ASA ...
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Страница 218: ...1 56 Cisco ASA Series CLI Configuration Guide Chapter 1 Managing Feature Licenses Feature History for Licensing ...
Страница 219: ...P A R T 2 Configuring High Availability and Scalability ...
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Страница 358: ...1 22 Cisco ASA Series CLI Configuration Guide Chapter 1 Information About Failover Failover Messages ...
Страница 403: ...P A R T 2 Configuring Interfaces ...
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Страница 499: ...P A R T 2 Configuring Basic Settings ...
Страница 500: ......
Страница 516: ...1 16 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Basic Settings Monitoring DNS Cache ...
Страница 533: ...P A R T 2 Configuring Objects and Access Lists ...
Страница 534: ......
Страница 558: ...1 4 Cisco ASA Series CLI Configuration Guide Chapter 1 Information About Access Lists Where to Go Next ...
Страница 601: ...P A R T 2 Configuring IP Routing ...
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Страница 632: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Defining Route Maps Feature History for Route Maps ...
Страница 680: ...1 48 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring OSPF Feature History for OSPF ...
Страница 745: ...P A R T 2 Configuring Network Address Translation ...
Страница 746: ......
Страница 780: ...1 34 Cisco ASA Series CLI Configuration Guide Chapter 1 Information About NAT Where to Go Next ...
Страница 844: ...1 32 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Twice NAT Feature History for Twice NAT ...
Страница 845: ...P A R T 2 Configuring AAA Servers and the Local Database ...
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Страница 859: ...1 13 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring AAA Servers and the Local Database Configuring AAA ...
Страница 871: ...1 25 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring AAA Servers and the Local Database Configuring AAA ...
Страница 981: ...P A R T 2 Configuring Access Control ...
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Страница 994: ...1 12 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Access Rules Feature History for Access Rules ...
Страница 1028: ...1 34 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Management Access Feature History for Management Access ...
Страница 1054: ...1 26 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring AAA Rules for Network Access Feature History for AAA Rules ...
Страница 1060: ...1 6 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Web Cache Services Using WCCP Feature History for WCCP ...
Страница 1061: ...P A R T 2 Configuring Service Policies Using the Modular Policy Framework ...
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Страница 1093: ...P A R T 2 Configuring Application Inspection ...
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Страница 1191: ...P A R T 2 Configuring Unified Communications ...
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Страница 1333: ...P A R T 2 Configuring Connection Settings and QoS ...
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Страница 1370: ...1 20 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring QoS Feature History for QoS ...
Страница 1379: ...P A R T 2 Configuring Advanced Network Protection ...
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Страница 1448: ...1 20 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Threat Detection Configuration Examples for Threat Detection ...
Страница 1474: ...1 18 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Filtering Services Monitoring Filtering Statistics ...
Страница 1475: ...P A R T 2 Configuring Modules ...
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Страница 1504: ...1 28 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring the ASA IPS Module Feature History for the ASA IPS module ...
Страница 1528: ...1 24 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring the ASA CX Module Feature History for the ASA CX Module ...
Страница 1548: ...1 20 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring the ASA CSC Module Feature History for the CSC SSM ...
Страница 1549: ...P A R T 2 Configuring VPN ...
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Страница 1592: ...1 42 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring IPsec and ISAKMP Supporting the Nokia VPN Client ...
Страница 1612: ...1 20 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring L2TP over IPsec Feature History for L2TP over IPsec ...
Страница 1796: ...1 6 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring the PPPoE Client Using Related Commands ...
Страница 1965: ...P A R T 2 Configuring Logging SNMP and Smart Call Home ...
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Страница 1988: ...1 22 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring Logging Feature History for Logging ...
Страница 2002: ...1 14 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring NetFlow Secure Event Logging NSEL Feature History for NSEL ...
Страница 2036: ...1 34 Cisco ASA Series CLI Configuration Guide Chapter 1 Configuring SNMP Feature History for SNMP ...
Страница 2059: ...P A R T 2 System Administration ...
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Страница 2098: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Troubleshooting Viewing the Coredump ...
Страница 2099: ...P A R T 2 Reference ...
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