拓扑如下：

    1,实验说明：
    ü Cisco 1721来模拟PPPOE  SERVER
    üPIX501来模拟PPPOE Client
    2,实验过程
    配置CISCO 1721为PPPOE SERVER
    //首先底层配置,这没什么说的，大家已经非常熟悉了~~
    Router(config)#no ip domain-lookup
    Router(config)#line console 0
    Router(config-line)#exec-timeout 0 0
    Router(config-line)#logg syn
    Router(config-line)#host PPPOE_SERVER
    PPPOE_SERVER(config)#int e0/0
    PPPOE_SERVER(config-if)#ip add 192.168.0.1 255.255.255.0
    PPPOE_SERVER(config-if)#no sh
    PPPOE_SERVER(config-if)#pppoe enable //接口下开启PPPOE 会话功能
    PPPOE_SERVER(config-if)#exit
    PPPOE_SERVER(config)#vpdn enable //全局开启VPDN服务
    PPPOE_SERVER(config)#vpdn-group PPPOE  //创建VPDN拨号组，此处我设置的名称为PPPOE，注意这里创建的组名要和PIX上启用的VPDN组名要一致，不然pppoe session会话失败
    PPPOE_SERVER(config-vpdn)#accept-dialin //接受拨号请求
    PPPOE_SER(config-vpdn-acc-in)#protocol pppoe //指定会话协议为pppoe
    PPPOE_SER(config-vpdn-acc-in)#virtual-template 1 //创建虚模板 1，表示第几个虚模板，创建虚模板之后，会立即看见Virtual-Access1, changed state to up
    PPPOE_SER(config-vpdn-acc-in)#end
    *Mar  1 00:06:27.707: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
    *Mar  1 00:06:28.707: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up

    PPPOE_SERVER#conf t
    Enter configuration commands, one per line.  End with CNTL/Z.
    PPPOE_SERVER(config)#int virtual-template 1 //进入虚模板1
    PPPOE_SERVER(config-if)#ip unnumbered e0/0 //此处不要给虚模板配置IP地址，建议使用ip unnumbered 向物理接口E0/0借用，因为E0/0接口为outside接口，已开启pppoe enable
    PPPOE_SERVER(config-if)#ppp authentication pap //指定ppp认证方式为pap，采用认证方式为PAP，认证过程会话用户名和密码为明文，你可以采用chap
    PPPOE_SERVER(config-if)#peer default ip address pool ADSL //指定地址池的名称为ADSL，可以随意指定名称，但要和下面的地址池名称一致
    PPPOE_SERVER(config-if)#exit
    PPPOE_SERVER(config)#ip local pool ADSL 200.0.0.1 200.0.0.10 //指定地址池的地址范围，这个地址范围必须是连续的
    PPPOE_SERVER(config)#username wangwanli password wangwanli //指定pppoe拨号的用户名和密码
    PPPOE_SERVER(config)#end
    到此PPPOE_SERVER上配置已全部完成
    PIX上进行配置
    pixfirewall> enable
    Password:
    pixfirewall#
    pixfirewall# conf t
    pixfirewall(config)# vpdn group PPPOE request dialout pppoe //指定vpdn会话名称PPPOE,这个名称与pppoe server上的VPDN组名是一致的
    pixfirewall(config)# vpdn group PPPOE localname wangwanli //指定vpdn本地用户名
    pixfirewall(config)# vpdn ?
    configure mode commands/options:
      group     Keyword to specify a group name
      username  Keyword to configure username
    pixfirewall(config)# vpdn group PPPOE ppp authentication pap //指定ppp认证方式为pap，与pppoe server认证方式一致
    pixfirewall(config)# vpdn username wangwanli password wangwanli //指定拨号的用户名和密码
    pixfirewall(config)# int e1
    pixfirewall(config-if)# no sh //激活接口
    pixfirewall(config-if)# nameif outside //定义接口为outside，默认的安全级别为0
    INFO: Security level for "outside" set to 0 by default.
    pixfirewall(config-if)# ip address pppoe setroute //从pppoe 服务器获得IP地址
    pixfirewall(config-if)# end
    到此PIX上的配置已经完成，如下是调试现象
    pixfirewall# debug ppp auth  //打开ppp 认证调试
    pixfirewall# debug pppoe event //打开pppoe 拨号事件请求
    debug pppoe event enabled at level 1
    pixfirewall# show ip address outside ?
      dhcp   Show DHCP lease information
      pppoe  Show PPPoE interface information
      |      Output modifiers
      <cr>
    pixfirewall# show ip address outside pppoe
    //PIX上完成拨号之后，查看得到的IP地址
    PPPoE Assigned IP addr: 200.0.0.1 255.255.255.255 on Interface: outside
       Remote IP addr: 192.168.0.1
    pixfirewall# show route

    Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
           D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
           N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
           E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
           i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
           * - candidate default, U - per-user static route, o - ODR
           P - periodic downloaded static route

    Gateway of last resort is 192.168.0.1 to network 0.0.0.0

    S*   0.0.0.0 0.0.0.0 [1/0] via 192.168.0.1, outside
    //查看路由表自动生成一条缺省路由
    pixfirewall# show interface ip brief
    Interface                  IP-Address      OK? Method Status                Protocol
    Ethernet0                  unassigned      YES unset  administratively down up
    Ethernet1                  200.0.0.1       YES manual up                    up
    Ethernet2                  unassigned      YES unset  up                    up
    Ethernet3                  unassigned      YES unset  administratively down up
    pixfirewall# ping 192.168.0.1
    Type escape sequence to abort.
    Sending 5, 100-byte ICMP Echos to 192.168.0.1, timeout is 2 seconds:
    !!!!!
    Success rate is 100 percent (5/5), round-trip min/avg/max = 10/20/50 ms
    //通过ping测试PIX与PPPOE SERVER是可以正常通信的
    pixfirewall# sh ip
    //PIX上接口IP地址信息
    System IP Addresses:
    Interface                Name                   IP address      Subnet mask     Method
    Ethernet1                outside                200.0.0.1       255.255.255.255 manual
    Current IP Addresses:
    Interface                Name                   IP address      Subnet mask     Method
    Ethernet1                outside                200.0.0.1       255.255.255.255 manua

    PPPOE_SERVER#show pppoe session all //查看pppoe session 所有会话详细信息
    Total PPPoE sessions 1

    PPPoE Session Information

    session id: 1
    local MAC address: cc9f.0788.0000, remote MAC address: 00aa.0001.0102
    virtual access interface: Vi1.1, outgoing interface: Et0/0
        117 packets sent, 117 received
    1915 bytes sent, 1934 received
    现在我把PIX上的E1接口重新关闭之后，再打开，再来观察一下PIX上的pppoe 的会话过程与PPPOE SERVER上的看到的pppoe 会话的四个过程，PADI---PADO-PADR-PADS 四个过程
    pixfirewall# conf t
    pixfirewall(config)# int e1
    pixfirewall(config-if)# sh
    PPPoE: Shutting down client session
    PPPoE: padi timer expired
    PPPoE: padi timer expired

    pixfirewall(config-if)# no sh
    pixfirewall# PPPoE: send_padi:(Snd) Dest:ffff.ffff.ffff Src:00aa.0001.0102 Type:0x8863=PPPoE-Discovery
    //开始发送广播，寻找PPPOE SERVER
    PPPoE: Ver:1 Type:1 Code:09=PADI Sess:0 Len:12
    PPPoE: Type:0101:SVCNAME-Service Name Len:0
    PPPoE: Type:0103:HOSTUNIQ-Host Unique Tag Len:4
    PPPoE: 00000001
    PPPoE: PPPoE:(Rcv) Dest:00aa.0001.0102 Src:cc9f.09e4.0000 Type:0x8863=PPPoE-Discovery
    PPPoE: Ver:1 Type:1 Code:07=PADO Sess:0 Len:48
    PPPoE: Type:0101:SVCNAME-Service Name Len:0
    PPPoE: Type:0103:HOSTUNIQ-Host Unique Tag Len:4
    PPPoE: 00000001
    PPPoE: Type:0102:ACNAME-AC Name Len:12
    PPPoE: PPPOE_Server

    PPPoE: Type:0104:ACCOOKIE-AC Cookie Len:16
    PPPoE: 9682A160
    PPPoE: 3EDB1E03
    PPPoE: DDDF8016
    PPPoE: 2E032E1C
    PPPoE:

    PPPoE: PADO

    PPPoE: send_padr:(Snd) Dest:cc9f.09e4.0000 Src:00aa.0001.0102 Type:0x8863=PPPoE-Discovery
    PPPoE: Ver:1 Type:1 Code:19=PADR Sess:0 Len:48
    PPPoE: Type:0101:SVCNAME-Service Name Len:0
    PPPoE: Type:0103:HOSTUNIQ-Host Unique Tag Len:4
    PPPoE: 00000001
    PPPoE: Type:0102:ACNAME-AC Name Len:12
    PPPoE: PPPOE_Server

    PPPoE: Type:0104:ACCOOKIE-AC Cookie Len:16
    PPPoE: 9682A160
    PPPoE: 3EDB1E03
    PPPoE: DDDF8016
    PPPoE: 2E032E1C
    PPPoE:

    PPPoE: PPPoE:(Rcv) Dest:00aa.0001.0102 Src:cc9f.09e4.0000 Type:0x8863=PPPoE-Discovery
    PPPoE: Ver:1 Type:1 Code:65=PADS Sess:3 Len:48
    PPPoE: Type:0101:SVCNAME-Service Name Len:0
    PPPoE: Type:0103:HOSTUNIQ-Host Unique Tag Len:4
    PPPoE: 00000001
    PPPoE: Type:0102:ACNAME-AC Name Len:12
    PPPoE: PPPOE_Server

    PPPoE: Type:0104:ACCOOKIE-AC Cookie Len:16
    PPPoE: 9682A160
    PPPoE: 3EDB1E03
    PPPoE: DDDF8016
    PPPoE: 2E032E1C
    PPPoE:
    PPPoE: PADS
    PPPoE: IN PADS from PPPoE tunnel
    PPPoE: Opening PPP link and starting negotiations.
    到这里PIX上的pppoe 会话已经结束，已经得到从PPPOE SERVER上分配的地址

    PPPOE SERVER上开启debug之后，收到PIX上的PPPOE 会话请求
    PPPOE_SERVER#
    *Mar  1 00:34:17.583: PPPoE 0: I PADI  R:00aa.0001.0102 L:ffff.ffff.ffff Et0/0
    *Mar  1 00:34:17.583: PPPoE 0: O PADO, R:00aa.0001.0102 L:cc9f.0788.0000 Et0/0
    *Mar  1 00:34:17.639: PPPoE 0: I PADR  R:00aa.0001.0102 L:cc9f.0788.0000 Et0/0
    *Mar  1 00:34:17.639: PPPoE : encap string prepared
    *Mar  1 00:34:17.639: [2]PPPoE 2: Access IE handle allocated
    *Mar  1 00:34:17.639: [2]PPPoE 2: pppoe SSS switch updated
    *Mar  1 00:34:17.639: [2]PPPoE 2: AAA unique ID allocated
    *Mar  1 00:34:17.643: [2]PPPoE 2: No AAA accounting method list
    *Mar  1 00:34:17.643: [2]PPPoE 2: Service request sent to SSS
    *Mar  1 00:34:17.643: [2]PPPoE 2: Created  R:cc9f.0788.0000 L:00aa.0001.0102 Et0/0
    *Mar  1 00:34:17.647: [2]PPPoE 2: State REQ_NASPORT    Event MORE_KEYS
    *Mar  1 00:34:17.647: [2]PPPoE 2: O PADS  R:00aa.0001.0102 L:cc9f.0788.0000 Et0/0
    *Mar  1 00:34:17.651: ppp2 PPP: Using default call direction
    *Mar  1 00:34:17.651: ppp2 PPP: Treating connection as a dedicated line
    *Mar  1 00:34:17.651: ppp2 PPP: Session handle[73000003] Session id[2]
    *Mar  1 00:34:17.651: ppp2 PPP: Authorization required
    *Mar  1 00:34:17.655: [2]PPPoE 2: State START_PPP    Event DYN_BIND
    *Mar  1 00:34:17.655: [2]PPPoE 2: data path set to PPP
    PPPOE_SERVER#
    *Mar  1 00:34:20.679: ppp2 PAP: I AUTH-REQ id 1 len 24 from "wangwanli"
    *Mar  1 00:34:20.679: ppp2 PAP: Authenticating peer wangwanli
    *Mar  1 00:34:20.687: ppp2 PPP: Sent PAP LOGIN Request
    *Mar  1 00:34:20.687: ppp2 PPP: Received LOGIN Response PASS
    *Mar  1 00:34:20.691: [2]PPPoE 2: State LCP_NEGO    Event PPP_LOCAL
    *Mar  1 00:34:20.691: PPPoE 2/SB: Sent vtemplate request on base Vi1
    *Mar  1 00:34:20.699: [2]PPPoE 2: State CREATE_VA    Event VA_RESP
    *Mar  1 00:34:20.699: [2]PPPoE 2: Vi1.1 interface obtained
    *Mar  1 00:34:20.699: [2]PPPoE 2: State PTA_BIND    Event STAT_BIND
    *Mar  1 00:34:20.699: [2]PPPoE 2: data path set to Virtual Acess
    PPPOE_SERVER#
    *Mar  1 00:34:20.703: [2]PPPoE 2: Connected PTA
    *Mar  1 00:34:20.707: Vi1.1 PPP: Sent LCP AUTHOR Request
    *Mar  1 00:34:20.707: Vi1.1 PPP: Sent IPCP AUTHOR Request
    *Mar  1 00:34:20.711: Vi1.1 LCP: Received AAA AUTHOR Response PASS
    *Mar  1 00:34:20.711: Vi1.1 IPCP: Received AAA AUTHOR Response PASS
    *Mar  1 00:34:20.711: Vi1.1 PAP: O AUTH-ACK id 1 len 5
    //PAP认证通过

    pixfirewall# show vpdn session pppoe state
    PPPoE Session Information (Total tunnels=1 sessions=1)
    SessID TunID Intf     State       Last Chg
        3      1 outside  SESSION_UP  2928 secs
    pixfirewall# show vpdn pppinterface //查看ppp会话，以及ppp认证方式
    PPP virtual interface id = 1
    PPP authentication protocol is PAP
    Server ip address is 192.168.0.1
    Our ip address is 200.0.0.1
    Transmitted Pkts: 122, Received Pkts: 121, Error Pkts: 0
    MPPE key strength is None
      MPPE_Encrypt_Pkts: 0,  MPPE_Encrypt_Bytes: 0
      MPPE_Decrypt_Pkts: 0,  MPPE_Decrypt_Bytes: 0
      Rcvd_Out_Of_Seq_MPPE_Pkts: 0

    pixfirewall#

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