Lab 13: Configuring Frame Relay Networks and Controlling Frame Relay ARP-Part I
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Lab 12: Configuring PPP Analog Backup for Synchronous Links ”Part IILab WalkthroughAttach two routers in a back-to-back manner using either V.35 cables or CSU/DSUs with a crossover cable, as depicted in Chapter 1 for additional help in configuring and attaching modems to a router's AUX port. The design requirements call for you to use EIGRP as the routing protocol. The requirements also call for you to dial only when the PPP circuit is lost. To force an interface to be in a standby mode and to pick up and dial only under a unique circumstance, Cisco offers the backup interface command. The backup interface command specifies that an interface stays idle until certain circumstances occur:
The backup interface command is used on the serial interface that is your primary interface. If you have a 2503 router, two serials, and one ISDN port, and if you were backing up the serial interface with the ISDN interface, the serial interface is referred to as the primary interface, and the ISDN is called the secondary. The backup interface command would go on the serial interface, called the primary interface, not the ISDN interface. The syntax for the backup command is as follows , entered in interface mode: backup interface interface_name_or_type You also can configure a time period specifying how much time should elapse before a secondary link status changes after primary link status has changed. There are two way to accomplish this:
As soon as the backup command is entered on an interface, it immediately forces it into a standby state. Example 4-29 shows a link in backup mode.When the interface is in this state, it does not respond to ping s. Example 4-29 Status of Link with the backup CommandAsync1 is standby mode, line protocol is down Hardware is Async Serial Internet address is 192.168.128.10/30 MTU 1500 bytes, BW 38 Kbit, DLY 100000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive not set DTR is pulsed for 5 seconds on reset LCP Closed Closed: IPCP, CDPCP In this circumstance, the backup command will come in handy. When deploying a backup strategy with the backup command, you should limit dialing to one side of the network. You might encounter scenarios in which multiple sites dial into the same BRI port or analog ports. If the backup command is places on both ends of the link, you run the risk of having the host stay in a down standby mode on one side of the link. A good example of this could be with Frame Relay, where each side of the link is dependent only on the local Frame Relay switch. In a Frame Relay network, it is possible of have one end of the link "Line UP, Protocol UP"; the backup command would not activate the secondary link, while, at the same time, the end of the Frame Relay network might be down. Therefore, it is recommended that you use the backup command only on the remote end of the link. With a backup strategy in mind, focus on configuring the branch router first. To configure the branch router, you need to perform the following:
After this is complete, your config should have parts that resemble the ones in Example 4-30. Example 4-30 Initial Setup of the sug_branchhostname sug_branch ! enable password cisco ! username sug_corp password 0 cub9biggs Before concerning yourself with the modem and the dial backup configuration, you should configure the host site. Configuring the sug_corp router is similar to configuring the sug_branch router. To configure the sug_corp router, perform the following actions:
After completing this, your configuration should resemble Example 4-31. Example 4-31 sug_corp Listinghostname sug_corp ! enable password cisco ! username sug_branch password 0 cub9biggs At this time, you should have full IP connectivity from the RS6000 to the mainframe. Test for full connectivity by issuing ping s from RS6000 to the mainframe. Also check the route table on each side of the network to ensure that the 172.16.1.0 and 172.200.1.0 networks are being advertised to each other. An EIGRP neighbor also should be built over the serial interface. Example 4-32 lists the route table on sug_branch followed by the show eigrp neighbors command. Example 4-32 Routing Table on sub_branch and show eigrp neighbor Commandsug_branch# show ip 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, * - candidate default U - per-user static route, o - ODR T - traffic engineered route Gateway of last resort is not set 192.168.128.0/24 is variably subnetted, 3 subnets, 2 masks D 192.168.128.8/30 [90/70440192] via 192.168.128.5, 00:09:19, Serial0 C 192.168.128.4/30 is directly connected, Serial0 C 192.168.128.5/32 is directly connected, Serial0 172.200.0.0/24 is subnetted, 1 subnets C 172.200.1.0 is directly connected, TokenRing0 172.16.0.0/24 is subnetted, 1 subnets D 172.16.1.0 [90/2195456] via 192.168.128.5, 00:09:19, Serial0 After you verify that routes are being exchanged and that an EIGRP neighbor is established, you can configure the dial backup portion of the lab. Starting with the sub_branch router, follow the four-step process for configuring PPP over asynchronous interfaces. The steps to do this are as follows:
The configuration for the async ports on both routers will be similar to those in past labs, with the main difference being that of a routing protocol. Under the async port, you will need to have the async default routing command for EIGRP. Because you will be using the backup interface command, the dialer list can permit all IP traffic on the sug_branch router. Until the backup interface command is added, you will see the link immediately dial if EIGRP is configured. If you perform a debug dialer, you will see that an EIGRP multicast is bringing up the dialer, as demonstrated in Example 4-33. Example 4-33 Example of debug dialer11:25:13: Async1: Dialing cause ip (s=192.168.128.10, d=224.0.0.10) On the sug_corp router, there will be no need for a dialer list because this side of the network will not be responsible for establishing or maintaining the link. Example 4-34 shows the configurations for the SuperGreat network in their entirety. Example 4-34 Complete Configurations for SuperGreat Network with Backuphostname sug_corp ! enable password cisco ! username sug_branch password 0 cub9biggs ! interface Ethernet0 ip address 172.16.1.1 255.255.255.0 ! interface Serial0 ip address 192.168.128.5 255.255.255.252 encapsulation ppp no fair-queue clockrate 64000 ppp authentication chap ! interface Async1 ip address 192.168.128.9 255.255.255.252 encapsulation ppp async default routing async mode interactive dialer in-band dialer idle-timeout 300 dialer map ip 192.168.128.10 name sug_branch broadcast 5496550 ppp authentication chap ! router eigrp 2001 network 192.168.128.0 network 172.16.0.0 no auto-summary ! ip classless ! line con 0 line aux 0 autoselect ppp modem InOut modem autoconfigure discovery transport input all rxspeed 38400 txspeed 38400 line vty 0 4 login ! end ________________________________________________________________ hostname sug_branch ! enable password cisco ! username sug_corp password 0 cub9biggs ip subnet-zero chat-script dialsug "" "ATZ&F" OK "ATDT5496870" TIMEOUT 60 CONNECT ! interface Serial0 ip address 192.168.128.6 255.255.255.252 no ip directed-broadcast encapsulation ppp no ip mroute-cache backup interface Async1 no fair-queue ppp authentication chap ! interface TokenRing0 ip address 172.200.1.1 255.255.255.0 no ip directed-broadcast ring-speed 16 ! interface Async1 ip address 192.168.128.10 255.255.255.252 no ip directed-broadcast encapsulation ppp dialer in-band dialer map ip 192.168.128.9 name sug_corp broadcast 5496870 dialer-group 1 async default routing async mode interactive ppp authentication chap ! router eigrp 2001 network 172.200.0.0 network 192.168.128.0 no auto-summary ! ip classless ! dialer-list 1 protocol ip permit ! line con 0 transport input none line aux 0 autoselect ppp script dialer dialsug modem InOut modem autoconfigure discovery transport input all speed 38400 line vty 0 4 login ! end The SuperGreat network can be tested for backup by unplugging or shutting down the serial interface on the corporate end. Immediately upon link loss, you should see the branch router call the remote. The routing table will then converge over the async interface. Example 4-35 highlights this process in effect. Example 4-35 Output from debug dialer and Route Table Convergence on the sug_branch Routersug_branch# show ip 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, * - candidate default U - per-user static route, o - ODR T - traffic engineered route Gateway of last resort is not set 192.168.128.0/24 is variably subnetted, 3 subnets, 2 masks D 192.168.128.8/30 [90/70440192] via 192.168.128.5, 00:04:19, Serial0 C 192.168.128.4/30 is directly connected, Serial0 C 192.168.128.5/32 is directly connected, Serial0 172.200.0.0/24 is subnetted, 1 subnets C 172.200.1.0 is directly connected, TokenRing0 172.16.0.0/24 is subnetted, 1 subnets D 172.16.1.0 [90/2195456] via 192.168.128.5, 00:04:43, Serial0 |
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