1-2
Cisco ASA Series CLI Configuration Guide
Chapter 1 Setting General VPN Parameters
Permitting Intra-Interface Traffic (Hairpinning)
The syntax is
sysopt connection permit-vpn
.
The command has no keywords or arguments.
The following example enables IPsec traffic through the ASA without checking ACLs:
hostname(config)#
sysopt connection permit-vpn
Note
Decrypted through-traffic is permitted from the client despite having an access group on the outside
interface, which calls a
deny ip any any
access list, while
no sysopt connection permit-vpn
is
configured.
Users who want to control access to the protected network via site-to-site or remote access VPN using
the
no sysopt permit-vpn
command in conjunction with an access control list (ACL) on the outside
interface are not successful.
In this situation, when management-access inside is enabled, the ACL is not applied, and users can still
connect to the ASA using SSH. Traffic to hosts on the inside network is blocked correctly by the ACL,
but decrypted through-traffic to the inside interface is not blocked.
The
ssh
and
http
commands are of a higher priority than the ACLs. In other words, to deny SSH, Telnet,
or ICMP traffic to the box from the VPN session, use
ssh
,
telnet
and
icmp
commands.
Permitting Intra-Interface Traffic (Hairpinning)
The ASA includes a feature that lets a VPN client send IPsec-protected traffic to another VPN user by
allowing such traffic in and out of the same interface. Also called “hairpinning”, this feature can be
thought of as VPN spokes (clients) connecting through a VPN hub (ASA).
In another application, hairpinning can redirect incoming VPN traffic back out through the same
interface as unencrypted traffic. This would be useful, for example, to a VPN client that does not have
split tunneling but needs to both access a VPN and browse the web.
shows VPN Client 1 sending secure IPsec traffic to VPN Client 2 while also sending
unencrypted traffic to a public web server.
Figure 1-1
VPN Client Using Intra-Interface Feature for Hairpinning
Client VPN
laptop 2
Client VPN
laptop 1
192.168.0.11
192.168.0.10
Unencrypted traffic
Ipsec/SSL encrypted traffic
192.168.0.0
Security
appliance
Public web
server
143170
Summary of Contents for 5505 - ASA Firewall Edition Bundle
Page 28: ...Glossary GL 24 Cisco ASA Series CLI Configuration Guide ...
Page 61: ...P A R T 1 Getting Started with the ASA ...
Page 62: ......
Page 219: ...P A R T 2 Configuring High Availability and Scalability ...
Page 220: ......
Page 403: ...P A R T 2 Configuring Interfaces ...
Page 404: ......
Page 499: ...P A R T 2 Configuring Basic Settings ...
Page 500: ......
Page 533: ...P A R T 2 Configuring Objects and Access Lists ...
Page 534: ......
Page 601: ...P A R T 2 Configuring IP Routing ...
Page 602: ......
Page 745: ...P A R T 2 Configuring Network Address Translation ...
Page 746: ......
Page 845: ...P A R T 2 Configuring AAA Servers and the Local Database ...
Page 846: ......
Page 981: ...P A R T 2 Configuring Access Control ...
Page 982: ......
Page 1061: ...P A R T 2 Configuring Service Policies Using the Modular Policy Framework ...
Page 1062: ......
Page 1093: ...P A R T 2 Configuring Application Inspection ...
Page 1094: ......
Page 1191: ...P A R T 2 Configuring Unified Communications ...
Page 1192: ......
Page 1333: ...P A R T 2 Configuring Connection Settings and QoS ...
Page 1334: ......
Page 1379: ...P A R T 2 Configuring Advanced Network Protection ...
Page 1380: ......
Page 1475: ...P A R T 2 Configuring Modules ...
Page 1476: ......
Page 1549: ...P A R T 2 Configuring VPN ...
Page 1550: ......
Page 1965: ...P A R T 2 Configuring Logging SNMP and Smart Call Home ...
Page 1966: ......
Page 2059: ...P A R T 2 System Administration ...
Page 2060: ......
Page 2098: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Troubleshooting Viewing the Coredump ...
Page 2099: ...P A R T 2 Reference ...
Page 2100: ......