安全 : Cisco IOS 防火墙

没有NAT 的三接口路由器的Cisco IOS防火墙配置

2015 年 8 月 28 日 - 机器翻译
其他版本: PDFpdf | 英语 (2015 年 4 月 22 日) | 反馈


目录


简介

本文提供了连接到互联网、运行自己的服务器的小型办公室的典型配置示例。与互联网的连接是通过串行线路实现。Ethernet 0 连接至内部网络(单个 LAN)。Ethernet 1 连接至 DMZ 网络,该网络有一个用于为外界提供服务的节点。ISP 已为公司分配网块 192.168.27.0/24。该网块平分给 DMZ 和子网掩码为 255.255.255.128 的内部 LAN。基本策略如下:

  • 允许内部网络中的用户连接至公用互联网上的任何服务。

  • 允许互联网上的任何人连接到DMZ服务器上的WWW、FTP和简单邮件转发协议(SMTP)业务,并进行域名系统(DNS)查询。外部人员因此能够查看公司网页,获取公司发布的供外部调用的文件,并向公司发送邮件。

  • 允许内部用户连接到DMZ服务器上的POP服务(收邮件),并进行远程登录(管理)。

  • 不允许DMZ上的任何东西发起任何连接,不管是到专用网络还是互联网的连接均不可以。

  • 审计所有越过防火墙与专用网络上的 SYSLOG 服务器进行的连接。内部网络中的计算机使用 DMZ 上的 DNS 服务器。所有接口均使用输入访问列表来防止欺骗。输出访问列表用于控制可以发送到任何指定接口的流量。

使用思科IOS�防火墙,没有NAT的参考的二接口路由器使用Cisco IOS防火墙配置为了配置一个两个接口路由器,不用NAT。

要使用思科 IOS 防火墙配置带 NAT 的双接口路由器,请参阅使用思科 IOS 防火墙配置带 NAT 的双接口路由器

先决条件

要求

本文档没有任何特定的要求。

使用的组件

本文档中的信息基于以下软件和硬件版本:

  • 具有防火墙功能集的思科 IOS 软件 12.2(15)T13 版本

  • 思科 7204 VXR 路由器

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始(默认)配置。如果您使用的是真实网络,请确保您已经了解所有命令的潜在影响。

规则

有关文档规则的详细信息,请参阅 Cisco 技术提示规则

配置

本部分提供有关如何配置本文档所述功能的信息。

注意: 使用命令查找工具仅限注册用户)可获取有关本部分所使用命令的详细信息。

网络图

本文档使用以下网络设置:

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配置

本文档使用以下配置。

7204 VXR 路由器
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 

验证

使用本部分可确认配置能否正常运行。

命令输出解释程序仅限注册用户)(OIT) 支持某些 show 命令。使用 OIT 可查看对 show 命令输出的分析。

  • show access-list - 验证在 running-configuration 中配置的访问列表的配置是否正确。

    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 - 验证日志记录命令的配置。

    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 - 验证每个接口的思科 IOS 防火墙检查规则的配置。

    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#

故障排除

配置 IOS 防火墙路由器后,如果连接不起作用,请确保已使用 ip inspect (定义的名称) in/out 命令对接口启用检查。在此配置中,ip inspect standard in 适用于接口 Ethernet 3/0,ip inspect standard out 适用于接口 Ethernet 3/1。

有关故障排除的更多信息,请参阅思科 IOS 防火墙配置故障排除

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Document ID: 13893