Section 4: ISDN (6 Points) | CCIE Routing and Switching Practice Labs

Configure ISDN on R3 and R5 using PPP. R3 and R5 should be able to ping each other across the ISDN link.

If you configured this correctly as shown in Example 6-39, you have scored 2 points.

Make sure that your routing protocol is passed across the ISDN link only when the connectivity is established.

If you configured this correctly as shown in Example 6-39, you have scored 2 points.

The key to configuring as requested is to avoid having ISDN advertise or pass traffic through the link when R5-fa0/0 is up. R3 and R5 are running CLNS, which makes the scenario even more interesting.

Example 6-39. R3 and R5 ISDN Configuration

 R3#sh run int bri0/0 Building configuration... Current configuration : 340 bytes ! interface BRI0/0  ip address 160.10.15.3 255.255.255.0  ip router isis  encapsulation ppp  dialer map clns 49.0004.0000.0000.0005.00 name R5 broadcast 2222  dialer map ip 160.10.15.5 name R5 broadcast 2222  dialer-group 1  isdn switch-type basic-ni  isdn spid1 1111  ppp authentication chap end R3# ! ! ________________________________________________________________ R5#sh run int bri0/0 Building configuration... Current configuration : 340 bytes ! interface BRI0/0  ip address 160.10.15.5 255.255.255.0  ip router isis  encapsulation ppp  dialer map clns 49.0004.0000.0000.0003.00 name R3 broadcast 1111  dialer map ip 160.10.15.3 name R3 broadcast 1111  dialer-group 1  isdn switch-type basic-ni  isdn spid1 2222  ppp authentication chap end R5# R5#ping 160.10.15.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 160.10.15.3, timeout is 2 seconds: 5w1d: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to up..!!! Success rate is 60 percent (3/5), round-trip min/avg/max = 32/33/36 ms R5# 5w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:1, changed state to up 5w1d: %ISDN-6-CONNECT: Interface BRI0/0:1 is now connected to 1111 R3

The ISDN link should only pass a routing protocol if R5-fa0/0 is down.

If you configured this correctly as shown in Example 6-40, you have scored 2 points.

Example 6-40. R5 Routing Backup Output and R2 Output Routing Table Verification

 R5#sh ip ro 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 not set O E2 196.1.8.0/24 [110/1] via 160.10.37.2, 02:01:59, Serial0/1 O E2 196.1.10.0/24 [110/1] via 160.10.37.2, 02:01:59, Serial0/1      140.200.0.0/24 is subnetted, 1 subnets O E2    140.200.10.0 [110/1] via 160.10.37.2, 02:01:59, Serial0/1      160.10.0.0/16 is variably subnetted, 18 subnets, 3 masks O IA    160.10.32.0/30 [110/128] via 160.10.37.2, 02:02:09, Serial0/1 i L1    160.10.33.0/24 [115/20] via 160.10.15.3, BRI0/0 O       160.10.38.0/24 [110/128] via 160.10.37.2, 02:02:09, Serial0/1 O       160.10.37.2/32 [110/64] via 160.10.37.2, 02:02:10, Serial0/1 O       160.10.37.1/32 [110/128] via 160.10.37.2, 02:02:10, Serial0/1 C       160.10.37.0/24 is directly connected, Serial0/1 O IA    160.10.11.0/24 [110/138] via 160.10.37.2, 02:02:10, Serial0/1 C       160.10.15.0/24 is directly connected, BRI0/0 C       160.10.15.3/32 is directly connected, BRI0/0 O       160.10.2.0/24 [110/65] via 160.10.37.2, 02:02:12, Serial0/1 O IA    160.10.3.0/24 [110/129] via 160.10.37.2, 02:02:12, Serial0/1 O       160.10.1.0/24 [110/129] via 160.10.37.2, 02:02:12, Serial0/1 i L1    160.10.6.0/24 [115/30] via 160.10.15.3, BRI0/0 O IA    160.10.7.0/24 [110/139] via 160.10.37.2, 02:02:12, Serial0/1 O       160.10.4.0/24 [110/129] via 160.10.37.2, 02:02:12, Serial0/1 C       160.10.5.0/24 is directly connected, Loopback0 C       160.10.25.0/24 is directly connected, FastEthernet0/1 i L1    160.10.22.0/24 [115/20] via 160.10.15.3, BRI0/0 O E2 196.1.2.0/24 [110/1] via 160.10.37.2, 02:02:02, Serial0/1      130.200.0.0/24 is subnetted, 1 subnets O E2    130.200.10.0 [110/100] via 160.10.37.2, 02:02:02, Serial0/1 O E2 193.118.1.0/24 [110/100] via 160.10.37.2, 02:02:02, Serial0/1 O E2 193.118.3.0/24 [110/100] via 160.10.37.2, 02:02:02, Serial0/1 O E2 193.118.2.0/24 [110/100] via 160.10.37.2, 02:02:02, Serial0/1 ! ! Routes from IS-IS domain are still coming via OSPF although R5-Fa0/0 is down. R2#show ip route      160.10.0.0/16 is variably subnetted, 18 subnets, 3 masks O       160.10.37.5/32 [110/64] via 160.10.37.5, 00:00:28, Serial0/1.1 C       160.10.32.0/30 is directly connected, Serial0/0 O E2    160.10.33.0/24 [110/100] via 160.10.37.5, 00:00:28, Serial0/1.1 C       160.10.38.0/24 is directly connected, Serial0/1.2 O       160.10.37.1/32 [110/64] via 160.10.37.1, 00:00:28, Serial0/1.1 C       160.10.37.0/24 is directly connected, Serial0/1.1 O IA    160.10.11.0/24 [110/74] via 160.10.37.1, 00:00:29, Serial0/1.1 O E2    160.10.15.0/24 [110/100] via 160.10.37.5, 00:00:29, Serial0/1.1 O E2    160.10.15.3/32 [110/100] via 160.10.37.5, 00:00:15, Serial0/1.1 C       160.10.2.0/24 is directly connected, Loopback0 O       160.10.3.0/24 [110/65] via 160.10.32.1, 00:03:32, Serial0/0 O       160.10.1.0/24 [110/65] via 160.10.37.1, 00:00:29, Serial0/1.1 O E2    160.10.6.0/24 [110/100] via 160.10.37.5, 00:00:29, Serial0/1.1 O IA    160.10.7.0/24 [110/75] via 160.10.37.1, 00:00:29, Serial0/1.1 O       160.10.4.0/24 [110/65] via 160.10.38.4, 00:00:29, Serial0/1.2 O       160.10.5.0/24 [110/65] via 160.10.37.5, 00:00:29, Serial0/1.1 O IA    160.10.25.0/24 [110/65] via 160.10.37.5, 00:00:29, Serial0/1.1 O E2    160.10.22.0/24 [110/100] via 160.10.37.5, 00:00:29, Serial0/1.1 R2#

Configure R3 to override specific cause codes that are sent to the switch in case of a disconnection. Should this event occur, ensure that R3 uses "Channel-Not-Available" code message.

To accommodate this and override the disconnect codes, use the isdn disconnect-cause command.

If you configured this correctly as shown in Example 6-41, you have scored 1 point.

Example 6-41. R5 Routing Backup Output

 R3#sh run int bri0/0 Building configuration... Current configuration : 345 bytes ! interface BRI0/0  ip address 160.10.15.3 255.255.255.0  ip router isis  encapsulation ppp  dialer map clns 49.0004.0000.0000.0005.00 name R5 broadcast 2222  dialer map ip 160.10.15.5 name R5 broadcast 2222  dialer-group 1  isdn switch-type basic-ni  isdn spid1 1111  isdn disconnect-cause not-available  ppp authentication chap end R3#