Configuring Frame Relay
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Lab 10: Configuring PPP, PAP, and Compression over Asynchronous Dialup ”Part IILab WalkthroughAttach the modem to the access server or auxiliary port with the Cisco rolled cable. Use the Cisco head-shell labeled Modem to attach the modem to the cable. In the lab, use line or port 8 of the access server. To configure skynet_lab, the access server, you need to perform your four-step process for configuring PPP over asynchronous links. Applying a slight modification to the steps so that they fit this specific lab, you have the following sequence:
First, you need to perform some initial setup on the access server. You set a host name and set an enable password: Router(config)# hostname skynet_lab skynet_lab(config)# enable password cisco Next , perform the show line command to verify the absolute line number to which the modem will be attached. If Telnet access is to be enabled, also note where the vty line numbers start. Example 4-16 demonstrates the show line command. Notice that line number for port 8 ”it is TTY port 8. The lines for Telnet sessions start on 18 and run through 22. Example 4-16 The show line Commandskynet_lab# show line Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int * 0 CTY - - - - - 0 0 0/0 - 1 TTY 9600/9600 - - - - - 0 0 0/0 - * 2 TTY 9600/9600 - - - - - 0 1 9/27 - 3 TTY 9600/9600 - - - - - 0 1 0/0 - 4 TTY 9600/9600 - - - - - 0 0 0/0 - 5 TTY 9600/9600 - - - - - 0 1 0/0 - 6 TTY 9600/9600 - - - - - 0 0 0/0 - 7 TTY 9600/9600 - - - - - 0 0 0/0 - 8 TTY 9600/9600 - - - - - 0 0 0/0 - Next, you need to configure line 8 for modem and PPP use. You need to use the autoselect during-login command to select what type of session starts on the line. If the client dials in with a terminal emulator, a TTY session starts. If the client starts a PPP session, a PPP session is negotiated. The autoselect ppp command must also be used to start the PPP session. You also must configure the modem on line 8. Because you do not know the modem type, the autoconfigure type default command is used. Example 4-17 demonstrates the configuration of line 8 for modem and PPP use. Example 4-17 Configuration of a Line for Modem and PPP Useskynet_lab# conf t Enter configuration commands, one per line. End with CNTL/Z. skynet_lab(config)# line 8 skynet_lab(config-line)# modem inout skynet_lab(config-line)# modem autoconfigure type default skynet_lab(config-line)# login local skynet_lab(config-line)# autoselect during-login skynet_lab(config-line)# autoselect ppp skynet_lab(config-line)# transport input all skynet_lab(config-line)# ^Z skynet_lab# To verify that the modem has been properly configured, use the show line x command ”in this case, show line 8. Here, you are checking that the modem is configured. You also might want to use the debug confmodem command to ensure that the AT string was properly received by the mode. Refer back to Chapter 1 for more information on debugging modems, such as using reverse Telnet. The asynchronous interface should be configured next. The asynchronous interface must match the line number that the modem is on ”in this case, 8. At this time, you also want to configure the asynchronous interface for PPP and PAP authentication. Windows 95/98 clients use PAP authentication to authenticate PPP. Example 4-18 shows how to configure PPP encapsulation and PAP authentication. Example 4-18 Configuring PPP Encapsulation and PAP Authenticationskynet_lab# conf t Enter configuration commands, one per line. End with CNTL/Z. skynet_lab(config)# int a8 skynet_lab(config-if)# encapsulation ppp skynet_lab(config-if)# ppp authentication pap skynet_lab(config-if)# exit skynet_lab(config)# username JP password trashman skynet_lab# The next step, demonstrated in Example 4-19, involves setting the IP address of the asynchronous interface and using the peer default ip address remote_ip_address command to assign an IP address to the PPP client dialing into the router. Example 4-19 Configuring Local and Remote IP Addressesskynet_lab(config)# int a8 skynet_lab(config-if)# ip address 192.168.1.5 255.255.255.252 skynet_lab(config-if)# peer default ip address 192.168.1.6 You now can configure the router for DDR. For DDR, you need to add the following the configurations under the asynchronous interface:
The dialer in-band allows for V.24 bis dialing. The dialer idle-timeout and dialer-group commands define interesting traffic and determine how long the line can be idle of that traffic before disconnecting. Finally, the async mode interactive command allows for incoming connections. Under the global configuration level, you need to enter a dialer-list 8 protocol ip permit command. The dialer list can be simple in this config because the router is not initiating a call or routing over the link. Example 4-20 shows the DDR configuration process. Example 4-20 Configuring DDRskynet_lab(config)# int a8 skynet_lab(config-if)# dialer in-band skynet_lab(config-if)# dialer idle-timeout 600 skynet_lab(config-if)# dialer-group 8 skynet_lab(config-if)# async mode interactive skynet_lab(config-if)# exit skynet_lab(config)# dialer-list 8 protocol ip permit skynet_lab(config)# When this is complete, you can begin to test the configuration. To test the modem, use the debug confmodem and debug modem commands, as mentioned in Chapter 1. Example 4-21 lists the output of these commands. Here, you can see that the router is properly sending an AT command to the modem. Example 4-21 Output from debug modem and debug confmodem Commandsskynet_lab# debug modem skynet_lab# debug confmodem d06h: TTY8: Line reset by "Exec" 1d06h: TTY8: Modem: IDLE->HANGUP 1d06h: TTY8: destroy timer type 0 1d06h: TTY8: destroy timer type 1 1d06h: TTY8: destroy timer type 3 1d06h: TTY8: destroy timer type 4 1d06h: TTY8: destroy timer type 2 1d06h: TTY8: dropping DTR, hanging up 1d06h: tty8: Modem: HANGUP->IDLE 1d06h: TTY8: restoring DTR 1d06h: TTY8: autoconfigure probe started 1d06h: TTY8: Modem command: --AT&F&C1&D2S0=1H0-- 1d06h: TTY8: Modem configuration succeeded 1d06h: TTY8: Detected modem speed 115200 1d06h: TTY8: Done with modem configuration Verifying that the physical layer is working, you can test the network layer. Begin by turning on the "Big D" for PPP: debug ppp Negotiation, debug ppp authentication, and debug ppp error. Initiate a PPP session to the router by a Windows 95/98/2000 workstation. In this particular lab, you are looking for four tasks to complete successfully:
Example 4-22 lists the debug output, showing all four phases completing successfully and assigning the proper IP address to the Windows 95/98 client. Example 4-22 debug Output from a Successful Dial Connectionskynet_lab# debug ppp negotiation skynet_lab# debug ppp authentication skynet_lab# debug ppp error 1d06h: As8 IPCP: Install route to 192.168.1.6 1d06h: %LINK-3-UPDOWN: Interface Async8, changed state to up 1d06h: As8 PPP: Treating connection as a callin 1d06h: As8 PPP: Phase is ESTABLISHING, Passive Open <PPP Initializes 1d06h: As8 LCP: State is Listen Most PPP problems become evident with the "Big D" enabled. Without the debug s, it becomes difficult to spot analog dialup errors. Make sure that all four phases are completed, followed by some source ping s from 172.16.1.1 to 192.168.1.6 to verify IP connectivity. Some of the most common problems to look for are as follows :
To increase performance on this link, you can enable MPPC on interface A8 and disable CDP. To enable MPPC compression, simply add the compress mppc command on the interface. After adding this command to the interface, you can see MPPC get successfully negotiated in Example 4-23. To disable CDP on the interface, use the no cdp enable command on the interface. Example 4-23 debug Output for MPPC Compression1d07h: As8 CCP: O CONFREQ [Closed] id 2 len 10 1d07h: As8 CCP: MS-PPC supported bits 0x00000001 (0x120600000001) <<<text omitted>>> 1d07h: As8 IPCP: SecondaryWINS 0.0.0.0 (0x840600000000) 1d07h: As8 CCP: I CONFREQ [REQsent] id 1 len 15 1d07h: As8 CCP: MS-PPC supported bits 0x00000001 (0x120600000001) 1d07h: As8 CCP: Stacker history 1 check mode EXTENDED (0x1105000104) 1d07h: As8 CCP: O CONFREJ [REQsent] id 1 len 9 1d07h: As8 CCP: Stacker history 1 check mode EXTENDED (0x1105000104) 1d07h: As8 IPCP: I CONFACK [REQsent] id 13 len 10 1d07h: As8 IPCP: Address 192.168.1.5 (0x0306C0A80105) 1d07h: As8 CCP: I CONFACK [REQsent] id 2 len 10 1d07h: As8 CCP: MS-PPC supported bits 0x00000001 (0x120600000001) 1d07h: As8 CCP: I CONFREQ [ACKrcvd] id 2 len 10 1d07h: As8 CCP: MS-PPC supported bits 0x00000001 (0x120600000001) 1d07h: As8 CCP: O CONFACK [ACKrcvd] id 2 len 10 1d07h: As8 CCP: MS-PPC supported bits 0x00000001 (0x120600000001) 1d07h: As8 CCP: State is Open NOTE If you use two routers to test the PAP connection instead of a router and workstation, you need to use the command ppp pap sent-username under the async interface for a successful PAP challenge to occur. Finally, Example 4-24 shows the complete configuration for skynet_lab. Example 4-24 Complete Listing of skynet_labhostname skynet_lab ! enable password cisco ! username JP password 0 trashman ip subnet-zero ! interface Ethernet0 ip address 172.16.1.1 255.255.255.0 no ip directed-broadcast ! <<<text omitted>>> ! interface Async8 ip address 192.168.1.5 255.255.255.252 no ip directed-broadcast encapsulation ppp no ip mroute-cache dialer in-band dialer idle-timeout 600 dialer-group 8 async mode interactive peer default ip address 192.168.1.6 compress mppc no cdp enable ppp authentication pap ! ip classless ! dialer-list 8 protocol ip permit ! line con 0 exec-timeout 0 0 transport input none line 1 7 transport input all line 8 autoselect during-login autoselect ppp login local modem InOut modem autoconfigure type default transport input all speed 115200 line 9 16 line aux 0 line vty 0 4 login local ! end skynet_lab# |
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