Cisco Internetwork Troubleshooting Correcting the Problem at the Physical and Data Link Layers © 2005 Cisco Systems, Inc. All rights reserved. CIT

© 2005 Cisco Systems, Inc. All rights reserved. CIT Commands Used to Correct Physical and Data Link Problems arp –d [*] End-system command for deleting a specific entry or the entire contents of an ARP table. duplex {full | half | auto} router(config-if)# Configures the method by which an interface exchanges data. no shutdown router(config-if)# Activates an interface.

© 2005 Cisco Systems, Inc. All rights reserved. CIT encapsulation router(config-if)# Configures an encapsulation type on an interface. clock rate router(config-if)# Configures a clock rate on an interface. speed {10 | 100 | auto} router(config-if)# Configures the speed at which an interface transmits data. Commands Used to Correct Physical and Data Link Problems (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. CIT Example: Correcting a Serial Interface Problem at the Physical Layer Next Animation Click for Animation

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanJose(config)#interface serial1/0 SanJose(config-if)#no shutdown SanJose(config-if)#exit SanJose# Dec 12 14:00:43: %SYS-5-CONFIG_I: Configured from console by console Dec 12 14:00:44: %LINK-3-UPDOWN: Interface Serial1/0, changed state to up Dec 12 14:00:45: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to up Correcting a Serial Interface Problem at the Physical Layer 1. Enter interface configuration mode. 2. Activate the interface. 3. Exit interface configuration mode.

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanJose#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/ YES NVRAM up up Serial1/ YES NVRAM up up SanJose# Verifying the Correct Operation of SanJose

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanFran#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/ YES NVRAM up up Serial1/ YES NVRAM up up SanFran# Verifying the Correct Operation of SanFran

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanFran#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60 ms SanFran# Verifying Connectivity Across the Network

© 2005 Cisco Systems, Inc. All rights reserved. CIT Example: Correcting a Frame Relay Problem at the Data Link Layer Next Animation Click for Animation

© 2005 Cisco Systems, Inc. All rights reserved. CIT Orlando(config)#interface serial 1/0 Orlando(config-if)#no frame-relay lmi-type ansi Orlando(config-if)#exit Orlando# Dec 16 21:56:46: %SYS-5-CONFIG_I: Configured from console by console Orlando# Dec 16 21:57:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to up Orlando# Dec 16 21:57:32: %DUAL-5-NBRCHANGE: IP-EIGRP 101: Neighbor (Serial1/0) is up: new adjacency Orlando# Correcting a Frame Relay Problem at the Data Link Layer 1. Enter interface configuration mode. 3. Exit interface configuration mode. 2. Change the LMI type to ANSI.

© 2005 Cisco Systems, Inc. All rights reserved. CIT Orlando#show interface serial 1/0 Serial1/0 is up, line protocol is up Hardware is PowerQUICC Serial Description: Frame Relay link to Daytona Internet address is /30 MTU 1500 bytes, BW 128 Kbit, DLY usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation FRAME-RELAY, loopback not set Keepalive set (10 sec) LMI enq sent 462, LMI stat recvd 185, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 1023 LMI type is CISCO frame relay DTE. Orlando# Verifying the LMI Type on Orlando

© 2005 Cisco Systems, Inc. All rights reserved. CIT Orlando#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60 ms Orlando# Verifying Connectivity Across the Network

© 2005 Cisco Systems, Inc. All rights reserved. CIT Next Animation Click for Animation Example: Correcting Ethernet Problems at the Physical and Data Link Layers

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanFran#clear counters Clear "show interface" counters on all interfaces [confirm] SanFran# Correcting an Ethernet Problem at the Physical and Data Link Layers

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanFran#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms SanFran# Testing the Connection on an Ethernet Interface

© 2005 Cisco Systems, Inc. All rights reserved. CIT SanFran#show interfaces ethernet 0 Ethernet0 is up, line protocol is up Hardware is Lance, address is fcb0 (bia fcb0) Internet address is /24 MTU 1500 bytes, BW Kbit, DLY 1000 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:02:38, output 00:00:00, output hang never Last clearing of "show interface" counters 00:04:20 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 5 packets input, 570 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 input packets with dribble condition detected 92 packets output, 7774 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out SanFran# Verifying That the Ethernet Connection Is Functioning Properly

© 2005 Cisco Systems, Inc. All rights reserved. CIT Next Animation Click for Animation Example: Correcting a Fast Ethernet Problem at the Physical and Data Link Layers

© 2005 Cisco Systems, Inc. All rights reserved. CIT Tampa(config)#interface fastethernet 0/1 Tampa(config-if)#duplex full Tampa(config-if)#^Z Tampa# Dec 12 14:00:43: %SYS-5-CONFIG_I: Configured from console by console Correcting a Fast Ethernet Problem at the Physical and Data Link Layers

© 2005 Cisco Systems, Inc. All rights reserved. CIT Tampa#clear counters Clear "show interface" counters on all interfaces [confirm] Tampa# Resetting the Counters on the Fast Ethernet Interface

© 2005 Cisco Systems, Inc. All rights reserved. CIT Tampa#show interfaces fastethernet 0/1 FastEthernet0/1 is up, line protocol is up Hardware is Fast Ethernet, address is 000a.8a (bia 000a.8a ) MTU 1500 bytes, BW Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s input flow-control is off, output flow-control is off packets output, bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 PAUSE output 0 output buffer failures, 0 output buffers swapped out Tampa# Verifying the Correction of the Duplex Mismatch on the Fast Ethernet Interface

© 2005 Cisco Systems, Inc. All rights reserved. CIT Example: Correcting a Problem at the Physical and Data Link Layers Animations Done Click for Animation

© 2005 Cisco Systems, Inc. All rights reserved. CIT Seattle(config)#vtp mode transparent Setting device to VTP TRANSPARENT mode. Seattle(config)#no vlan 2 Seattle(config)#no vlan 3 Seattle(config)#no vlan 4 Seattle(config)#vlan 27 Seattle(config-vlan)#name Core_27 Seattle(config-vlan)#vlan 28 Seattle(config-vlan)#name Core_28 Seattle(config-vlan)#^Z Seattle# Dec 18 11:05:42: %SYS-5-CONFIG_I: Configured from console by console Dec 18 11:06:07: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan27, changed state to up Dec 18 11:06:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan28, changed state to up Seattle# Correcting the VTP Mode on Seattle

© 2005 Cisco Systems, Inc. All rights reserved. CIT Seattle# Dec 18 11:06:13: %BGP-5-ADJCHANGE: neighbor Up Dec 18 11:06:20: %BGP-5-ADJCHANGE: neighbor Up Seattle#show vlan VLAN Name Status Ports default active Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10, Fa0/11, Fa0/12, Fa0/13 Fa0/14, Fa0/15, Fa0/16, Fa0/17 Fa0/18, Fa0/19, Fa0/20, Fa0/21 Fa0/22, Fa0/23, Fa0/24, Gi0/1 Gi0/2 27 Core_27 active 28 Core_28 active 1002 fddi-default active 1003 token-ring-default active... Verifying VLAN Status on Seattle

© 2005 Cisco Systems, Inc. All rights reserved. CIT Seattle#show ip route... Gateway of last resort is to network B /16 [20/0] via , 00:00:20 B /16 [20/0] via , 00:00:20 B /16 [20/0] via , 00:00:20 B /16 [20/0] via , 00:00:21 B /16 [20/0] via , 00:00: /16 is variably subnetted, 7 subnets, 2 masks D /25 [90/ ] via , 23:19:43, FastEthernet0/5 C /25 is directly connected, Loopback0 D /25 [90/156160] via , 23:19:43, FastEthernet0/5... B /24 [20/0] via , 00:00:22 S* /0 [1/0] via Seattle# Verifying Network Routes on Seattle

© 2005 Cisco Systems, Inc. All rights reserved. CIT Seattle#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms Seattle# Verifying Connectivity Across the Network

© 2005 Cisco Systems, Inc. All rights reserved. CIT Cisco Systems Cisco Systems TAC: Internetwork Troubleshooting Handbook Cisco Systems technologies reference Support Resources for Correcting Physical and Data Link Layer Problems

© 2005 Cisco Systems, Inc. All rights reserved. CIT Standards Organizations Internet Engineering Task Force International Telecommunications Union Frame Relay Forum ATM Forum Support Resources for Understanding the Physical and Data Link Layer

© 2005 Cisco Systems, Inc. All rights reserved. CIT Procedure for Correcting Physical and Data Link Layer Problems 1 Verify that you have a valid saved configuration for any device on which you intend to modify the configuration. 3 Evaluate and document the results of each change that you make. 4 Verify that the changes you made actually fixed the problem without introducing any new problems. 5 Continue making changes until the problem appears to be solved. 6 If necessary, get input from outside resources. 2 Make initial configuration changes. 7 After the problem is resolved, document the solution.

© 2005 Cisco Systems, Inc. All rights reserved. CIT Summary Use the appropriate end system or Cisco commands and applications to correct an isolated problem. These are some physical and data link support resources: –Cisco Systems TAC –Internetwork Troubleshooting Handbook –Cisco Systems technologies reference Following a systematic procedure increases the chances that you will successfully and effectively correct an isolated problem at the physical or data link layer.

Completed Troubleshooting Logs © 2005 Cisco Systems, Inc. All rights reserved. CIT

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Core Router/Switch interface Port-channel11 no shut interface Port-channel12 no shut ! Troubleshooting LogTrouble Ticket B Core Router/Switch a) Users cannot get server or Internet

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Distribution Router Nothing neededNo issues Troubleshooting Log–Trouble Ticket B Distribution Router

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Access Router controller T1 0/0 linecode b8zs ! Serial interface 0/0:1 and 0/0:0 are down Troubleshooting Log–Trouble Ticket B Access Router

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Access Switch interface FastEthernet0/2 switchport access vlan 2 ! interface FastEthernet0/4 switchport access vlan 4 ! Some PCs ca not connect to anything Troubleshooting Log–Trouble Ticket B Access Switch

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Core Router/Switch vlan 27 name Core_27 ! vlan 28 name Core_28 ! int fas 0/5 duplex full speed 100 ! Troubleshooting Log–Trouble Ticket C Core Router/Switch a) Users cannot get server or Internet b) No connectivity to Distr rtr

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Distribution Router ! controller T1 0/0 no channel-group 0 timeslots 1-2 channel-group 0 timeslots 1-12 ! interface Serial0/0:0 description Fast Link to Daytona ip address no shut ! router eigrp 101 no passive-interface Serial0/0:0 ! Serial 0/0:0 and 0/0:1 are down (wrong channel group configured on ser 0/0:0); fixing channel group deletes no passive interface in EIGRP Troubleshooting Log–Trouble Ticket C Distribution Router

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Access Router ! a) interface FastEthernet0/0 speed 100 b) controller T1 0/0 framing esf ! Troubleshooting Log–Trouble Ticket C Access Router a) Fa 0/0 is down due to speed mismatch, users cannot get to anywhere b) Serial interface 0/0:1 and 0/0:0 are down

© 2005 Cisco Systems, Inc. All rights reserved. CIT ProblemSolution Access Switch Nothing neededNo issues Troubleshooting Log–Trouble Ticket C Access Switch