When the PC clients run a Point-to-Point over Ethernet (PPPoE) client application, the Cisco Digital Subscriber Line (DSL) Router is configured as a pure bridge and the troubleshooting steps are the same as a pure bridging scenario. If you troubleshoot the Cisco DSL Router and determine that it is operating correctly, contact your Internet Service Provider (ISP) or the PPPoE client application vendor for additional assistance.
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This document is not restricted to specific software and hardware versions.
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There are many reasons why your DSL connection might not function properly. The goal of this section is to isolate the cause of the failure and repair it. The first troubleshooting step is to determine which layer of your Asymmetric Digital Subscriber Line (ADSL) service is failing. There are three layers in which the failure can occur.
Layer 1 – DSL physical connectivity to your ISP Digital Subscriber Line Access Multiplexer (DSLAM)
Layer 2.1 – ATM connectivity
Layer 2.2 – Point-to-Point Protocol over ATM (PPPoA), PPPoE, RFC1483 Bridging, or RFC1483 Routing
Layer 3 – IP
The easiest way to determine which layer you should begin to troubleshoot is to issue the command show ip interface brief. The output of this command differs slightly depending on your configuration.
827-ESC#show ip interface brief Interface IP-Address OK? Method Status Protocol ATM0 unassigned YES manual up up ATM0.1 unassigned YES unset up up Ethernet0 10.10.10.1 YES manual up up
If the statuses of ATM0 and ATM0.1 are up and the protocol is up, begin to troubleshoot at Layer 2.
If the ATM interfaces are down, or if they continue to come up and then go down (they do not stay up and up), begin to troubleshoot at Layer 1.
If the CD light is on, go to the Layer 2 Issues section of this document.
If the CD light is off, continue with the next question.
Verify this information with your ISP.
If the DSL port is not plugged into the DSL wall jack, connect the port to the wall with a 4-pin or 6-pin RJ-11 cable. This is a standard telephone cable.
Issue this command in enable mode on the router in order to determine if the ATM0 interface is administratively down.
Router#show interface atm 0 ATM0 is administratively down, line protocol is down <... snipped ...>
If the ATM0 interface status is administratively down, issue the no shutdown command under the ATM0 interface.
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface atm 0 Router(config-if)#no shut Router(config-if)#end Router#write memory
If the ATM0 interface status is down and down, the router does not see a carrier on the ADSL line. This generally indicates one of two issues:
The active pins on the DSL wall jack are incorrect.
Your ISP has not turned up a DSL service on this wall jack.
Cisco DSL Router xDSL Port Pinouts
The RJ-11 connector provides an xDSL connection to external media via a standard RJ-11 6-pin modular jack.
In order to determine if the ATM0 interface is down and down, issue the show interface atm 0 command from enable mode of the router:
Router#show interface atm 0 ATM0 is down, line protocol is down <... snipped ...>
If the ATM interface is down and down—not administratively down—check the pinout of your DSL wall jack. The DSL Router uses a standard RJ-11 (4-pin or 6-pin) cable to provide the ADSL connection to the wall jack. The center pair of pins on the RJ-11 cable is used to carry the ADSL signal (pins 3 and 4 on a 6-pin cable, or pins 2 and 3 on a 4- pin cable).
If you are sure you have the right pins on the wall jack and the ATM0 interface is still down and down, replace the RJ-11 cable between the ADSL port and your wall jack. If the interface is still down and down after you replace the RJ-11 cable, contact your ISP and have the ISP verify that DSL service has been enabled on the wall jack you use.
If you are not sure what pins on your wall jack are active, ask your ISP.
If you have verified that your ADSL cable is good and that you have the correct pinouts, the next step is to make sure you have the correct power supply for the 827.
Note: The 827 does not use the same power supply as other 800 Series Routers.
In order to determine if you have the correct power supply, on the back of the power adapter look for Output +12V 0.1A, -12V 0.1A, +5V 3A, -24V 0.12A, and -71V 0.12A. If your power supply is missing the +12V and -12V feeds, then it is for a different Cisco 800 Series Router and does not work on the 827. Note that if you use the wrong power supply, the Cisco 827 powers up but is unable to train up (connect) to the ISP DSLAM.
If everything up to this point in the Layer 1 troubleshooting procedure is correct, the next step is to make sure you have the correct DSL operating mode. Cisco recommends that you use dsl operating-mode auto if you are not sure what DMT technology your ISP uses. These are the commands to configure operating-mode autodetection:
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface atm 0 Router(config-if)#dsl operating-mode auto Router(config-if)#end Router#write memory
Obtain this information from your ISP or telephone company.
Complete these steps in order to determine whether you have the correct virtual path identifier/virtual circuit identifier (VPI/VCI) values configured on the router.
Verify your version of Cisco IOS® software.
Important: This does not work with Cisco IOS Software Release 12.1(1)XB.
Router#show version !--- Used to determine your Cisco IOS software release. Cisco Internetwork Operating System Software IOS (tm) C820 Software (C820-OSY656I-M), Version 12.1(3)XG3, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1) !--- The two lines immediately preceding appear on one line on the router. TAC:Home:SW:IOS:Specials for info Copyright (c) 1986-2000 by cisco Systems, Inc. Compiled Wed 20-Dec-00 16:44 by detang Image text-base: 0x80013170, data-base: 0x80725044 <... snipped ...>
Configure the router for debug logging.
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#logging console Router(config)#logging buffer Router(config)#service timestamp debug datetime msec Router(config)#service timestamp log datetime msec Router(config)#end Router#write memory Building configuration... [OK] Router#terminal monitor
Enable debugging on the router.
Router#debug atm events ATM events debugging is on Router# 2d18h: 2d18h: RX interrupt: conid = 0, rxBd = 0x80C7EF74 length=52 2d18h: Data Cell received on vpi = 8 vci = 35 !--- Your VPI/VCI. 2d18h: 2d18h: RX interrupt: conid = 0, rxBd = 0x80C7EEC0 length=52 2d18h: Data Cell received on vpi = 8 vci = 35 2d18h: 2d18h: RX interrupt: conid = 0, rxBd = 0x80C7EECC length=52 2d18h: Data Cell received on vpi = 8 vci = 35 2d18h: 2d18h: RX interrupt: conid = 0, rxBd = 0x80C7EED8 length=52 2d18h: Data Cell received on vpi = 8 vci = 35
Make sure you have debug ATM events that run on the Cisco DSL Router, and then go to a working Internet connection and begin to ping the IP address your ISP statically assigned to you.
It does not matter whether you have configured this IP address on the Cisco DSL Router. What is important is that your ATM interface is up/up and that you ping the IP address your ISP gave you. If you do not see the expected output after the ping test, contact your ISP for support.
Disable debugging on the router.
<< wait 60 seconds >>
Router#undebug all !--- Used to turn off the debug events. All possible debugging has been turned off.
Verify your VPI/VCI values, and then make the necessary changes to your configuration. If you do not see output during the 60 seconds of debugging, contact your ISP.
In a bridged environment, pinging the default gateway is a good test of connectivity. In general, if you can ping to your default gateway, you know that Layer 1 and Layer 2 services function properly. Open an MS-DOS window and try to ping the default gateway.
C:\>ping 192.168.1.1 Pinging 192.168.1.1 with 32 bytes of data: Reply from 192.168.1.1: bytes=32 time<10ms TTL=247 Reply from 192.168.1.1: bytes=32 time<10ms TTL=247 Reply from 192.168.1.1: bytes=32 time<10ms TTL=247 Reply from 192.168.1.1: bytes=32 time<10ms TTL=247 Ping statistics for 192.168.1.1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms
If your success rate is 80 to 100 percent, try to ping a valid Internet address (18.104.22.168 is www.cisco.com). If you can ping the default gateway from the PC but you cannot ping another Internet address, make sure you have only one static default route in the configuration (for example, IP route 0.0.0.0 0.0.0.0 192.168.1.1).
For the previous example, if you already have a correct static default route and cannot ping Internet addresses, contact your ISP in order to resolve the routing issue.
If the ping test fails, you see output similar to this. In this case, continue with the troubleshooting steps that follow.
C:\>ping 192.168.1.1 Pinging 192.168.1.1 with 32 bytes of data: Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for 192.168.1.1: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms
For your Cisco DSL Router to forward packets to your ISP, your bridged interface must be in a forwarding state. If your bridged interface is in a blocking state, there is a loop in your network that you have to remove before you are able to pass traffic. The most common cause of a loop in a DSL network is to have two bridged DSL circuits to the same ISP.
Router#show spanning-tree Bridge group 1 is executing the ieee compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0001.96a4.a8bc Configured hello time 2, max age 20, forward delay 15 Current root has priority 32768, address 0000.0c25.36f4 Root port is 3 (ATM0), cost of root path is 1562 Topology change flag not set, detected flag not set Number of topology changes 2 last change occurred 00:00:56 ago from Ethernet0 Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15 Timers: hello 0, topology change 0, notification 0, aging 300 Port 2 (Ethernet0) of Bridge group 1 is forwarding Port path cost 100, Port priority 128, Port Identifier 128.2. Designated root has priority 32768, address 0000.0c25.36f4 Designated bridge has priority 32768, address 0001.96a4.a8bc Designated port id is 128.2, designated path cost 1562 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 44, received 0 Port 3 (ATM0) of Bridge group 1 is forwarding Port path cost 1562, Port priority 128, Port Identifier 128.3. Designated root has priority 32768, address 0000.0c25.36f4 Designated bridge has priority 32768, address 0000.0c25.36f4 Designated port id is 128.17, designated path cost 0 Timers: message age 2, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 2, received 53 Router#
When you are sure that your bridged interface is forwarding, you need to determine if you have the Layer 2 media access control (MAC) address of the gateway router of your ISP. Use the show bridge command to check for the Layer 2 address. This command lists all the Layer 2 entries for a specific bridge group.
In this example, there are two entries in the bridge table. The first entry is the MAC address of the PC client in the LAN. The second entry is the MAC address of the ISP gateway router (default gateway). If the MAC address of the ISP gateway router is not in the bridge table, contact your ISP in order to verify your network settings.
Router#show bridge Total of 300 station blocks, 298 free Codes: P - permanent, S - self Bridge Group 1: Address Action Interface Age RX count TX count 0010.a492.e1d2 forward Ethernet0 4 163 4 0010.7bb9.bd1a forward ATM0 0 4 3 Router#
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