思科asa5505防火墙配置

### Cisco ASA5505 Firewall Configuration Guide

#### Basic Setup and VLAN Creation

To configure the basic setup of a Cisco ASA 5505 firewall, one must start by creating Virtual LANs (VLANs). The process involves assigning ports to specific VLANs and setting security levels for these VLANs. This method establishes distinct security zones within the network environment[^1].

For instance:

interface Ethernet0/0
 switchport access vlan 2
!
interface Vlan2
 nameif outside
 security-level 0
 ip address 192.168.1.1 255.255.255.0
!
interface Ethernet0/1
 switchport access vlan 3
!
interface Vlan3
 nameif inside
 security-level 100
 ip address 172.16.1.1 255.255.255.0

This configuration assigns `Ethernet0/0` to an external-facing VLAN named "outside," while `Ethernet0/1` connects internally through another VLAN called "inside."

#### Addressing Interface IP Issues

When configuring interface addresses on the ASA device, ensure that the chosen subnet does not conflict with any existing DHCP pools or other interfaces' subnets. If there's a mismatch between the configured IP address and the expected subnet mask, errors may occur during the assignment attempt.

An example command sequence might look like this when encountering such issues:

CCNAS-ASA(config-if)#no ip address
CCNAS-ASA(config-if)#ip address 192.29.6.1 255.255.255.0

If problems persist after verifying all settings are correct, consider checking whether the assigned IP falls into the proper range defined by your organization’s networking policies[^2].

#### Configuring Site-to-Site IPSec Tunnel

Establishing secure connections across different sites requires defining tunnel groups along with specifying encryption parameters using Internet Protocol Security (IPSec).

Here is how to set up a site-to-site IPSec tunnel group:

tunnel-group 218.249.X.X type ipsec-l2l
tunnel-group 218.249.X.X ipsec-attributes
 pre-shared-key donglai123

In addition to establishing trust relationships via shared keys, further configurations would involve setting up crypto maps and applying them appropriately based on organizational requirements[^3].