Basic ISDN Configuration 6 Points
The basic ISDN configuration task information is as follows:
■ ISDN switch information:
— ISDN switch type: basic-5ess
■ ISDN numbering:
■ SPIDs are not required.
Configure the ISDN interfaces on R3 and R5 as follows:
■ Ensure that only R3 can call R5, and R3 should never challenge R5 for a username or password pairing.
■ ISDN switch type is basic-5ess. Do not configure any SPIDs.
■ If traffic exceeds more than 65 percent, the second ISDN B channel will be used. (Hint: Enable ppp multilink.)
■ If there is an error rate of 20 percent or higher, the interface on R3 should show only a DOWN status when the command show interface bri0/0 is displayed. (Hint: Use the ppp quality command.)
■ R5 cannot call R3 under any circumstance. If R3 OSPF adjacency goes down, make sure that the ISDN link is operational and that all OSPF routing is accomplished through the ISDN link. Use ospf demand circuit and not static or dialer-watch statements.
■ Use PPP encapsulation and the strongest authentication available.
■ When the ISDN is active, all routers must be able to ping and telnet the local ISDN interfaces on R3 and R5.
■ Ensure that OSPF neighbors are not keeping the ISDN call active unless the neighbor over the Frame-Relay link is not adjacent. (Hint: Apply the no peer neighbor-route IOS command on R3 and R5.)
■ Use the command show isdn status to confirm when any ISDN calls are activated or deactivated.
Basic ISDN Configuration Solution
R3 and R5 are connected to an ISDN switch. All the ISDN parameters are provided so that you can configure them easily. An OSPF demand circuit is enabled between R3 and R5.
Example 8-57 configures R3 for ISDN connectivity to R5.
Example 8-57 ISDN Configuration for R3
Hostname R3 !
username R5 password 0 cisco !
isdn switch-type basic-5ess interface BRI0/0 description 7775010
ip address 144.254.7.1 255.255.255.252 encapsulation ppp ip ospf message-digest-key 1 md5 cisco ip ospf authentication message-digest ip ospf demand-circuit ip ospf network point-to-point ppp quality 80
dialer map ip 144.254.7.2 name R5 broadcast 7775020 dialer load-threshold 165 either no peer neighbor-route dialer-group 1 isdn switch-type basic-5ess ppp authentication chap callin ppp multilink
!Global command below permits IP traffic only dialer-list 1 protocol ip permit
In Example 8-57, R3 is configured for OSPF demand circuit. Only when OSPF is adjacent to R3 and R4 is down, will R3 make an outgoing ISDN call to R5. IP data is permitted to cross the ISDN
link via the dialer group command. OSPF authentication is enabled because area 0 requires all interfaces configured for authentication to have authentication configured and enabled with the correct secret key. PPP CHAP authentication is used because CHAP encrypts all passwords with MD5. The ppp quality command ensures that if error rates on the interface are reaching 20 percent (80 percent or less is good traffic), the interface will be brought down. This is a specific IOS command.
Example 8-58 enables R5 to receive the call. Example 8-58 R5 ISDN Configuration hostname R5 !
username R3 password 0 cisco !
interface BRI0/0 description 7775020
ip address 144.254.7.2 255.255.255.252 encapsulation ppp ip ospf authentication message-digest ip ospf message-digest-key 1 md5 cisco dialer load-threshold 165 either dialer map ip 144.254.7.1 name R3 broadcast ip ospf network point-to-point dialer-group 1 isdn switch-type basic-5ess no peer neighbor-route ppp authentication chap callin ppp multilink !
dialer-list 1 protocol ip permit
R5 cannot make an outgoing call because the dial map statement contains no valid ISDN number. The ppp multilink command is enabled so that two B channels can be active when R3 outbound traffic reaches 65 percent or more. The ppp authentication chap callin command checks only for R3 username and password, and ensures that R3 does not challenge R5 for a username or password. Notice that R5 is not configured for OSPF demand circuit because R3 makes the outgoing call, and, to obtain OSPF adjacency, only the remote edge router needs to have demand circuit enabled.
Example 8-59 displays the OSPF exchange when the Frame-Relay link is not active or when the OSPF dead interval expires between R3 and R4.
Example 8-59 ISDN Call on R3
R3#show debug Dial on demand:
Dial on demand events debugging is on IP routing:
OSPF adjacency events debugging is on OSPF events debugging is on
|
3w6d |
OSPF |
144.254.153.1 address 144.254.3.3 on Serial0/0 is dead, |
state |
DOWN |
|
3w6d |
OSPF |
Neighbor change Event on interface Serial0/0 |
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|
3w6d |
OSPF |
DR/BDR election on Serial0/0 |
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3w6d |
OSPF |
Elect BDR 0.0.0.0 |
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3w6d |
OSPF |
Elect DR 144.254.154.1 |
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|
3w6d |
DR: 144.254.154.1 (Id) BDR: none |
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3w6d |
OSPF |
144.254.154.1 address 144.254.3.1 on Serial0/0 is dead, |
state |
DOWN |
|
3w6d |
%OSPF-5-ADJCHG: Process 1, Nbr 144.254.154.1 on Serial0/0 from |
FULL |
to DOW |
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|
R3# |
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3w6d: |
OSPF |
Neighbor change Event on interface Serial0/0 |
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|
3w6d: |
OSPF |
DR/BDR election on Serial0/0 |
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3w6d: |
OSPF |
Elect BDR 0.0.0.0 |
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3w6d: |
OSPF |
Elect DR 0.0.0.0 |
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|
3w6d: |
DR: none BDR: none |
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|
3w6d: |
OSPF |
Remember old DR 144.254.154.1 (id) |
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3w6d: |
OSPF |
Build router LSA for area 0, router ID 144.254.153 |
1, seq 0x80000269 |
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|
3w6d: |
OSPF |
Send with youngest Key 0 |
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3w6d: |
BR0/0 |
DDR: Dialing cause ip (s=144.254.7.1, d=224.0.0.5) |
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3w6d: |
BR0/0 |
DDR: Attempting to dial 7775020 |
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3w6d: |
%LINK |
3-UPDOWN: Interface BRI0/0:2, changed state to up |
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3w6d: |
%LINK |
3-UPDOWN: Interface Virtual-Access1, changed state |
to up |
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3w6d: |
Vi1 DDR: Dialer statechange to up |
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3w6d: |
Vi1 DDR: Dialer call has been placed |
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3w6d: |
%LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:2 |
changed state to |
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|
up |
||||
3w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Accessl, changed s tate to up
3w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state t o down
3w6d: OSPF: Send with youngest Key 0
3w6d: %ISDN-6-CONNECT: Interface BRI0/0:2 is now connected to 7775020 R5
Example 8-59 displays the debug output when an ISDN call is made to R5 after OSPF neighbor adjacencies between R3 and R4 are terminated. The debug output shows that the neighbor adjacency state to R4 failing and an outgoing call to R3 being made followed by a successful OSPF adjacency.
Example 8-60 confirms OSPF neighbor adjacency to R5 and the fact that IP routing is now over the ISDN interface BRIO/O.
Example 8-60 show ip ospf neighbor on R3 R3#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
144.254.155.1 1 FULL/ - - 144.254.7.2 BRI0/0
144.254.152.1 0 FULL/DROTHER 00:01:19 144.254.4.2 FastEthernet0/ 0
144.254.0.0/16 is variably subnetted, 12 subnets, 5 masks O IA 144.254.6.0/29 [110/1563] via 144.254.7.2, 00:03:29, BRI0/0 O IA 144.254.5.0/27 [110/1563] via 144.254.7.2, 00:03:29, BRI0/0 O E1 144.254.2.0/30 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0 O 144.254.3.0/29 [110/1611] via 144.254.7.2, 00:03:29, BRI0/0
O E1 144.254.1.0/30 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0 O 144.254.154.0/24 [110/1564] via 144.254.7.2, 00:03:29, BRI0/0
O IA 144.254.155.0/24 [110/1563] via 144.254.7.2, 00:03:29, BRI0/0 O 144.254.152.0/24 [110/1612] via 144.254.7.2, 00:03:29, BRI0/0
O E1 144.254.151.0/24 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0
131.108.0.0/24 is subnetted, 3 subnets O E1 131.108.3.0 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0 O E1 131.108.2.0 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0 O E1 131.108.1.0 [110/1663] via 144.254.7.2, 00:03:29, BRI0/0 R3#
Finally, ensure that when ISDN is active, the ISDN subnet, 144.254.7.0/30, is reachable from all parts of the network.
Example 8-61 confirms the subnet in the routing table on the furthest router from R3, namely R1.
Example 8-61 show ip route on R1 R1#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
Example 8-61 show ip route on R1 (Continued)
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 144.254.1.2 to network 0.0.0.0
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D |
EX |
144 |
254 |
6 |
0/29 |
[170/302364416] via 144.254.2.2, 02:06:49, Tunnel0 |
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D |
EX |
144 |
254 |
7 |
0/30 |
[170/302364416] via 144.254.2.2, 00:16:26, Tunnel0 |
|
D |
EX |
144 |
254 |
4 |
0/26 |
[170/302364416] via 144.254.2.2, 01:26:04, Tunnel0 |
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D |
144 |
254 |
5 |
0/27 |
[90/297270016] via 144.254.2.2, 02:06:49, Tunnel0 |
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|
C |
144 |
254 |
2 |
0/30 |
is directly connected, Serial0/1 |
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D |
144 |
254 |
3 |
0/29 |
[90/297756416] via 144.254.2.2, 02:06:49, Tunnel0 |
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C |
144 |
254 |
1 |
0/30 |
is directly connected, Ethernet0/0 |
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D |
144 |
254 |
154.0/24 [90/297372416] via 144.254.2.2, 02:06:50, Tunnel0 |
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D |
EX |
144 |
254 |
155.0/24 [170/302364416] via 144.254.2.2, 01:23:27, Tunnel0 |
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D |
EX |
144 |
254 |
152.0/24 [170/302364416] via 144.254.2.2, 02:06:50, Tunnel0 |
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D |
EX |
144 |
254 |
153.0/24 [170/302364416] via 144.254.2.2, 00:16:17, Tunnel0 |
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C |
144 |
254 |
151.0/24 is directly connected, Loopback0 |
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131.10! |
3.0.0/16 is |
variably subnetted, 4 subnets, 2 masks |
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C |
131 |
108 |
3 |
0/24 |
is directly connected, Loopback3 |
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C |
131 |
108 |
2 |
0/24 |
is directly connected, Loopback2 |
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C |
131 |
108 |
1 |
0/24 |
is directly connected, Loopback1 |
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D |
131 |
108 |
0 |
0/22 |
is a summary, 02:57:04, Null0 |
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R* |
0.0.0. |
0/0 |
[120/1 |
via 144.254.1.2, 00:00:01, Ethernet0/0 |
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Example 8-62 displays a successful ping request from R1 to R3 BRI0/0 and R5 BRI0/0. Example 8-62 Ping 144.254.7.1 and 144.254.7.2fromR1
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R1#ping 144.254.7.1 |
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Type escape sequence to abort. |
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Sending 5, 100-byte ICMP Echos to !!!!! |
144.254.7.1 |
timeout is |
2 |
seconds: |
|
Success rate is 100 percent (5/5) |
round-trip |
min/avg/max |
= |
36/38/40 ms |
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R1#ping 144.254.7.2 |
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Type escape sequence to abort. |
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Sending 5, 100-byte ICMP Echos to !!!!! |
144.254.7.2 |
timeout is |
2 |
seconds: |
|
Success rate is 100 percent (5/5) |
round-trip |
min/avg/max |
= |
4/6/8 ms |
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R1# |
NOTE The show isdn status IOS command details if any calls are active. R3 must have a call active only when the Frame-Relay connection to R4 is not routing IP. The following display is taken when the Frame-Relay link is operational:
R3#show isdn status
Global ISDN Switchtype = basic-5ess ISDN BRI0/0 interface dsl 0, interface ISDN Switchtype = basic-5ess Layer 1 Status:
ACTIVE Layer 2 Status:
TEI = 64, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status:
0 Active Layer 3 Call(s) Active dsl 0 CCBs = 0
The Free Channel Mask: 0x80000003 Total Allocated ISDN CCBs = 0
Currently, there are no Layer 3 calls. When the ISDN interface is operational, you should see, at most, two calls. The following display is taken when one ISDN B channel is active:
R3#show isdn status
Global ISDN Switchtype = basic-5ess ISDN BRI0/0 interface dsl 0, interface ISDN Switchtype = basic-5ess Layer 1 Status:
ACTIVE Layer 2 Status:
TEI = 64, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status:
1 Active Layer 3 Call(s)
CCB:callid=803F, sapi=0, ces=1, B-chan=1, calltype=DATA Active dsl 0 CCBs = 1 The Free Channel Mask: 0x80000002 Total Allocated ISDN CCBs = 1
You should also use show commands in any CCIE lab to make sure you have satisfied the questions, as just seen, in the case of ensuring ISDN is active only when a failure occurs.
Continue reading here: Dynamic Access List Lock and Key Feature 5 Points
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