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This chapter presents troubleshooting information for connectivity and performance problems in tag switching (TS) environments. For an overview of tag switching on the ATM switch. See the chapter "Configuring Tag Switching" in the LightStream 1010 ATM Switch Software Configuration Guide.
This section assumes that you have confirmed that all physical port and network connections are working correctly using the information in the chapters "Troubleshooting ATM Switch Interface Connections" and "Troubleshooting ATM Switch Network Connections."
This chapter is separated into the following:
Tag switching is a high-performance packet-forwarding technology that assigns tags to mulitprotocol frames for transport across packet- or cell-based networks.
In conventional Layer 3 forwarding, as a packet traverses the network, each router extracts forwarding information from the Layer 3 header. Header analysis is repeated at each router (hop) through which the packet passes.
In a tag switching network, the Layer 3 header is analyzed just once. It is then mapped into a short fixed-length tag. At each hop, the forwarding decision is made by looking at the value of the tag only. There is no need to reanalyze the Layer 3 header. Because the tag is a fixed length, an unstructured value, looking it up is fast and simple.
A tag switching network consists of tag edge routers and tag switches, as shown in Figure 7-1. Tag edge routers are located at the edge of a tag switching network. They use standard routing protocols---such as Open Shortest Path First (OSPF)---to create routing tables, that identify routes through the network. Based on the routing tables, tag edge routers use the Tag Distribution Protocol (TDP) to apply and distribute tags to other tag edge routers or tag switches. Tag switches are located at the core of a tag switching network. They receive TDP information from the tag edge routers and build their own forwarding database. Tag switches then switch the packets based on the tags only (without looking at the Layer 3 header).
When a tag edge router at the entry point of a tag switching network receives a packet for forwarding:
1. The router analyzes the network layer header and performs any applicable network layer services such as security, accounting, or quality of service (QoS) classification.
2. The router chooses a route for the packet based on the information in its routing table, applies a tag, and forwards the packet to the next-hop tag switch.
3. The tag switch receives the tagged packet and switches the packet from switch to switch based on the tag only. The switches do not reanalyze the network layer header; they look only at the short fixed-length tag.
4. The packet reaches the tag edge router at the exit point of the tag switched network, where the tag is removed and the packet is delivered.
In the example network (see Figure 7-1) the primary campus network backbone is made up of two LightStream 1010 switches connected to two Cisco routers:
This network example is used to describe the troubleshooting examples in the rest of this chapter.
For detailed configuration information about tag switching refer to the chapter "Configuring Tag Switching" in the LightStream 1010 ATM Switch Software Configuration Guide.
This section describes initial troubleshooting steps that you should perform when first troubleshooting a tag switching connection.
At the LightStream 1010 ATM switch use the following commands to check the tag switching configuration:
| Command | Task |
|---|---|
Confirm the TDP identifier for the TS ATM switches or routers that might to be malfunctioning. | |
Confirm that each tag switching ATM switch or router can connect to the TDP identifier of its neighbor. | |
Confirm that tag switching is enabled on the switch. | |
Confirm the tag switching configuration on the ATM interface. | |
Confirm the tag switching VPI range on an interface. | |
Confirm the loopback interface 0 configuration. | |
Confirm the OSPF configuration. |
Use the following steps to confirm the TDP identifier for the TS switches or routers that might be malfunctioning:
Step 1 Use the show tag tdp discovery command to determine the tag discovery protocol identifier of the tag switching ATM switch.
AdminFl1Ls1# show tag-switching tdp discovery
Local TDP Identifier: 172.20.40.161:0 TDP Discovery Sources: Interfaces:
ATM1/0/0: xmit/recv TDP Id: 150.0.0.1:1 ATM3/0/0.10: xmit/recv TDP Id: 160.0.0.1:1 AdminFl1Ls1#
Step 2 Check the Local TDP Ident field. This indicates field the TDP identifier for the local TS ATM switch or router for this session.
Step 3 Check the Interfaces field. This field displays the interfaces engaging in TDP discovery activity:
If either xmit or recv do not appear, refer to the chapter "Configuring Tag Switching," of the LightStream 1010 ATM Switch Software Configuration Guide.
Use the following steps to Ping each tag switching ATM switch or router. This process confirms that each can connect to the TDP identifier of the neighbor:
Step 1 Use the ping command to confirm the connection to the TDP of the neighbor.
AdminFl1Ls1# ping
Protocol [ip]: Target IP address: 180.0.0.1
Repeat count [5]: Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: y
Source address or interface: 140.0.0.1
Type of service [0]: Set DF bit in IP header? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Loose, Strict, Record, Timestamp, Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. Sending 5, 100-byte ICMP Echoes to 180.0.0.1, timeout is 2 seconds: !!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 184/398/1188 ms AdminFl1Ls1#
Step 2 Check the Success rate field. This field should indicate 100 percent. If not, continue with the following troubleshooting steps.
Use the following steps to confirm that tag switching is configured on the ATM switch and its interfaces:
Step 1 Use the show running-config command to confirm that tag switching is enabled on the switch.
AdminFl1Ls1# show running-config
Building configuration... Current configuration: ! version 11.3 no service pad ! <Information deleted> ! interface ATM0/1/1ip unnumbered Loopback0
tag-switching ip ! interface ATM1/0/0 ip address 150.0.0.1 255.255.255.224
tag-switching ip ! <Information deleted> ! end AdminFl1Ls1#
Step 2 Check the tag switching ATM switch interface to confirm that tag switching is enabled on the connections.
For detailed interface configuration information about tag switching, refer to the section "Enabling Tag Switching on the ATM Interface," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
Use the following steps to display the status of TDP sessions. The neighbor information branch can have information about all TDP neighbors or can be limited to the neighbor with a specific IP address or, TDP identifier, or to TDP neighbors known to be accessible over a specific interface.
Step 1 Use the show tag-switching tdp neighbor command to display the status of TDP sessions.
AdminFl1Ls1# show tag-switching tdp neighbor
Peer TDP Ident: 1.0.12.12:2; Local TDP Ident 1.0.11.11:2
TCP connection: 1.0.12.12.11008 - 1.0.11.11.711
State: Oper; PIEs sent/rcvd: 2199/2198; Downstream on demand
Up time: 02:31:58 TDP discovery sources: ATM0/0/1 Peer TDP Ident: 1.0.12.12:8; Local TDP Ident 1.0.11.11:7 TCP connection: 1.0.12.12.11015 - 1.0.11.11.711 State: Oper; PIEs sent/rcvd: 2119/2130; Downstream on demand Up time: 02:31:39 TDP discovery sources: ATM0/1/0.19 Peer TDP Ident: 1.0.12.12:7; Local TDP Ident 1.0.11.11:6 TCP connection: 1.0.12.12.11016 - 1.0.11.11.711 State: Oper; PIEs sent/rcvd: 2120/2119; Downstream on demand Up time: 02:31:38 TDP discovery sources: ATM0/1/0.18
Step 2 Check the Peer TDP Ident field. This field indicates the TDP identifier of the neighbor (peer device) for this session.
Step 3 Check the Local TDP Ident field. This field indicates the TDP identifier for the local TS switch or router for this session.
Step 4 Check the TCP connection field. This field indicates the TCP connection used to support the TDP session. The format for displaying the TCP connection is peer IP address.peer port local IP address.
Step 5 Check the PIEs sent/rcvd field. This field indicates the number of TDP protocol information elements (PIEs) sent to and received from the session peer device. The count includes the transmission and receipt of periodic keepalive PIEs, which are required for maintenance of the TDP session.
Step 6 Check the Up time field. This field indicates the length of time the TDP session has existed.
Use the following steps to confirm the tag switching interface configuration on the ATM switch:
Step 1 Use the show tag-switching interface command to confirm the configuration and connection of the tag switching interfaces.
AdminFl1Ls1# show tag-switching interface
Interface IP Tunnel Operational ATM1/0/0 Yes No Yes ATM3/0/0 Yes No Yes AdminFl1Ls1#
Step 2 Check the IP field. This field indicates whether the interface is configured to tag IP packets.
Step 3 Check the Operational field. This field shows whether the packets are being tagged.
Step 4 Use the show tag interface detail command to confirm the tag switching VPI range on interface.
AdminFl1Ls1# show tag interface detail
Interface ATM1/0/0:
IP tagging enabled
TSP Tunnel tagging not enabled
Tagging not operational
MTU = 4470
ATM tagging: Tag VPI = 1, Control VC = 0/32
Interface ATM3/0/0:
IP tagging enabled
TSP Tunnel tagging not enabled
Tagging not operational
MTU = 4470
ATM tagging: Tag VPI range = 5 - 6, Control VC = 6/32
<Additional text omitted.>
Step 5 Check the IP tagging enabled field. This field indicates whether Tag Switching is enabled on this interface.
Step 6 Check the ATM tagging field. This field indicates the VPI range of the interface.
For detailed interface configuration information about tag switching, refer to the section "Enabling Tag Switching on the ATM Interface," chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
Use the following steps to confirm the loopback interface 0 configuration on the ATM switch:
Step 1 Use the show interface loopback 0 command to confirm the loopback interface 0 configuration on the switch.
AdminFl1Ls1# show interface loopback 0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 2.2.2.2/24
MTU 1500 bytes, BW 8000000 Kbit, DLY 5000 usec, rely 255/255, load 1/255
Encapsulation LOOPBACK, loopback not set, keepalive set (10 sec)
Last input 00:00:03, output never, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/0, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 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
73 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
AdminFl1Ls1#
Step 2 Check the Loopback 0 status field. It should be up.
Step 3 Check the line protocol field. It should be up.
Step 4 Check the Internet address field. It should display the IP address of the loopback interface on this ATM switch.
For detailed interface configuration information about loopback, refer to the section "Configuring a Loopback Interface," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
Use the following steps to confirm the OSPF configuration on the ATM switch:
Step 1 Use the show ip ospf command to confirm the OSPF configuration of the ATM switch.
AdminFl1Ls1# show ip ospf
Routing Process "ospf 10000" with ID 150.0.0.0 Supports only single TOS(TOS0) routes SPF schedule delay 5 secs, Hold time between two SPFs 10 secs Number of DCbitless external LSA 0 Number of DoNotAge external LSA 0 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Area BACKBONE(0) (Inactive) Number of interfaces in this area is 3 Area has no authentication SPF algorithm executed 2 times Area ranges are Link State Update Interval is 00:30:00 and due in 00:28:44 Link State Age Interval is 00:20:00 and due in 00:18:44 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 0 AdminFl1Ls1#
Step 2 Check the Routing Process field. The ospf number and ID number should match the numbers configured.
If not, refer to the OSPF configuration information, refer to the section "Configuring OSPF," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
This section describes troubleshooting TDP control channel virtual path identifier (VPI) and virtual channel identifier (VCI).
Although not necessary for most configurations, you can change the default VPI and VCI of the TDP control channel if you want to use a nondefault value.
Use the following commands to check the tag switching TPD neighbor connections:
| Commands | Task |
|---|---|
Confirm the tag switching TDP neighbor connection. |
Use the following steps to check the tag switching TPD neighbor connections:
Step 1 Use the show tag-switching tdp neighbor command to confirm the tag switching TDP neighbor connections:
Step 2 Check the Peer TDP Ident field. This field indicates the TDP identifier of the neighbor (peer device) for this session.
Step 3 Check the Local TDP Ident field. This field indicates the TDP identifier for the local TS switch or router for this session.
Step 4 Check the TCP connection field. This field indicates the TCP connection used to support the TDP session. The format for displaying the TCP connection is peer IP address.peer port local IP address.
Step 5 Check the PIEs sent/rcvd field. This field indicates the number of TDP PIEs sent to and received from the session peer device. The count includes the transmission and receipt of periodic keepalive PIEs, which are required for maintenance of the TDP session.
Step 6 Check the Up time field. This field indicates the length of time the TDP session has existed.
Use the following steps to confirm the VPI and VCI configuration of the tag switching interface on the ATM switch interface:
Step 1 Use the show tag interface atm card/subcard/port detail command to confirm the configuration and connection of the tag switching interface VPI and VCI.
Switch# show tag interfaces atm 0/0/1 detail
Interface ATM0/0/1:
IP tagging enabled
TSP Tunnel tagging not enabled
Tagging operational
MTU = 8940
ATM tagging: Tag VPI range = 2 - 5, Control VC = 6/32
Switch#
Step 2 Check the IP tagging field. This field shows whether the interface is configured to tag IP packets.
Step 3 Check the Tagging operational field. This field shows whether the packets are being tagged.
Step 4 Check the ATM tagging field. This field indicates the VPI range of the interface.
For detailed tag switching VPI and VCI configuration information, refer to the section "Configuring a VPI Range," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide,
This section describes troubleshooting a tag switching connection configured on a VP tunnel.
For detailed information about VP tunnel tag switching configuration refer to the section "Configuring Tag Switching on VP Tunnels," in the chapter "Configuring Tag Switching" in the LightStream 1010 ATM Switch Software Configuration Guide.
To confirm VP tunnel configuration of tag switching, perform the following task in EXEC mode:
| Command | Task |
|---|---|
Confirm the VP tunnel configuration on an interface. | |
show tag-switching tsp-tunnels {ip_address | all | head | middle | tail | remote} [tunnel-interface-num] [brief] | Confirm the TSP1 tunnel status and configuration. |
| 1TSP = tag switching path |
Use the following steps to confirm the VP tunnel configuration of tag switching:
Step 1 Use the show atm vp command to confirm VP tunnel configuration.
EngFl1Ls1# show atm vp
Interface VPI Type X-Interface X-VPI Status ATM4/0/0 51 PVP ATM1/1/0 101 UP ATM1/1/0 101 PVP ATM3/0/0 51 UP EngFl1Ls1#
Step 2 Check the Status field. The PVP status should be up. If not, check the VP tunnel configuration. Refer to the section "Configuring Tag Switching on VP Tunnels" in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
Use the following steps to confirm the tag switching VP tunnel configuration:
Step 1 Use the show tag-switching tsp-tunnels command to confirm VP tunnel configuration on each router or ATM switch in the network. The following example starts at the headend:
EngFL1LS1# show tag-switching tsp-tunnels
Signalling Summary:
TSP Tunnels Process: running
RSVP Process: running
Forwarding: enabled
TUNNEL ID DESTINATION STATUS CONNECTION
10.106.0.6 0 10.2.0.12 up up
EngFL1LS1#
Step 2 Use the show tag-switching tsp-tunnels command to confirm VP tunnel configuration at the middle ATM switch(es) or router(s):
AdminFL1LS1# show tag-switching tsp-tunnels
Signalling Summary:
TSP Tunnels Process: running
RSVP Process: running
Forwarding: enabled
TUNNEL ID DESTINATION STATUS CONNECTION
10.106.0.6 0 10.2.0.12 up up
AdminFL1LS1#
Step 3 Use the show tag-switching tsp-tunnels command to confirm VP tunnel configuration at the tailend ATM switch or router:
AdminFL1Rt1# show tag-switching tsp-tunnels
Signalling Summary:
TSP Tunnels Process: running
RSVP Process: running
Forwarding: enabled
TUNNEL ID DESTINATION STATUS CONNECTION
10.106.0.6 0 10.2.0.12 up up
AdminFL1Rt1#
Step 4 Verify that the TSP Tunnels Process is running. If not, enter the tag-switching tsp-tunnels command to enable the process globally on the ATM switch or router.
Step 5 Verify that the RSVP Process is running. If not, enter the tag-switching tsp-tunnels command on the interfaces used by the tunnel to enable the process on the interface.
Step 6 If this is a router connection, verify that Forwarding is enabled on the router. If not, enter the ip cef distributed switch or ip cef switch commands to enable IP Cisco Express Forwarding (CEF) globally on the router.
Step 7 Use the show tag-switching interface command to check the VP tunnel interface configuration at each ATM switch or router in the tunnel. The following example starts at the headend:
EngFl1Ls1# show tag-switching interface
Interface IP Tunnel Operational
ATM4/0/0 Yes No Yes
ATM1/1/0 Yes No Yes
EngFl1Ls1#
Step 8 Use the show tag-switching interface command to check the VP tunnel interface configuration at the middle ATM switch(es) or router(s):
AdmminFl1Ls1# show tag-switching interface
Interface IP Tunnel Operational
ATM3/0/0 Yes Yes Yes
ATM1/0/0 Yes Yes Yes
AdminFl1Ls1#
Step 9 Use the show tag-switching tsp-tunnels command to confirm VP tunnel configuration at the tailend ATM switch or router:
AdmminFl1Rt1#show tag-switching interface
Interface IP Tunnel Operational
ATM0/0 Yes Yes Yes
Ethernet 2/3 Yes Yes Yes
AdminFl1Rt1#
Step 10 Verify that the interfaces used by the tunnel have Yes in the Tunnel column.
If not, use the tag-switching tsp-tunnels command on the interface(s) used by the tunnel to enable TSP tunnels.
Refer to the section "Configuring Tag Switching on VP Tunnels," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
Step 11 Verify the interfaces used by the tunnel are operational. The interfaces should have Yes under the Operational column.
If not, check the interface configuration and refer to the section "Configuring Tag Switching on VP Tunnels," in the chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
This section describes debug commands that you can use to troubleshoot tag switching connections on an ATM switch.
Use the following commands to debug tag switching connections on an ATM switch:
| Command | Task |
|---|---|
Debug tag switching adjacency database events. | |
Debug tag switching ATM Tag Distribution Protocol (TDP) events. | |
Debug tag switching packets. | |
debug tag-switching tdp {advertisements | bindings | directed-neighbors | pies [received | sent] | session [io | state] | transport [connections | events | timers]} | Debug TDP switching events. |
Debug tag switching Tag Forwarding Information Base (TFIB). | |
debug tag-switching traffic-eng {events | interfaces | metrics | routing-table} | Debug tag switching traffic engineering. |
debug tag-switching tsp-tunnels {events | signalling | tagging} | Debug tag switching TSP tunnels. |
For detailed interface configuration information, refer to the section "Enabling Tag Switching on the ATM Interface," in chapter "Configuring Tag Switching," in the LightStream 1010 ATM Switch Software Configuration Guide.
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