This chapter provides troubleshooting information about connectivity and performance problems in the Layer 2 network connections of an ATM switch router and includes the following sections:
Note For detailed cabling and hardware information for each port adapter, refer to the
Catalyst 8540 CSR Route Processor and Interface Module Installation Guide.
Layer 2 Switching and Bridging Overview
This section provides some overview information about Layer 2 switching and bridging.
Layer 2 Switching
The difference between Layer 2 and Layer 3 switching is the type of information inside the frame that is used to determine the correct output interface. With Layer 2 switching, frames are switched based on MAC address information. With Layer 3 switching, frames are switched based on network-layer information.
Layer 2 switching does not look inside a packet for network-layer information as does Layer 3 switching. Layer 2 switching is performed by looking at a destination MAC address within a frame. It looks at the frame destination address and sends it to the appropriate interface if the switch knows the destination address location. Layer 2 switching builds and maintains a switching table that keeps track of which MAC addresses belong to each port or interface.
If the Layer 2 switch does not know where to send the frame, it broadcasts the frame out to all its ports on the network, to learn the correct destination. When the frame reply is returned, the switch learns the location of the new address, and adds the information to the switching table.
The switch router performs Layer 2 switching using the following functions:
Places path destination address, source address, and VLAN information are stored in CAM tables.
Sends MAC Address update information to the route processor via Cisco IOS Interprocess Communications (IPC).
Considers Ethernet processor interface learning as "normal"
Updates the route processor from the Ethernet processor interface.
Broadcasts use and Broute VC to communicate with ports on other modules in same bridge group.
Sets spanning tree sets state of IOS-CPU.
Transmitted by IOS-CPU, and received by a Layer 2 ASIC, bridge PDUs are tunneled in the IPC messages.
Receives Bridge PDUs on trunk ports, and preserves port and tag information.
During transmission, bridge PDUs are tagged by the ASICs on trunk ports
Bridging
Cisco IOS software supports transparent bridging for Ethernet. In addition, Cisco supports all the mandatory Management Information Base (MIB) variables specified for transparent bridging in RFC 1286.
Cisco IOS software bridging functionality combines the advantages of a spanning tree bridge and a full multiprotocol router. This combination provides the speed and protocol transparency of an adaptive spanning tree bridge, along with the functionality, reliability, and security of a router.
The switch router can be configured to serve as both an IP and IPX router and a MAC-level bridge, bridging any traffic that cannot otherwise be routed. For example, a router routing IP traffic can also bridge the Digital local-area transport (LAT) protocol or NetBIOS traffic.
To configure bridging, you must perform the following tasks:
In global configuration mode:
Select Spanning Tree Protocol.
Assign a priority to the bridge (optional).
In interface configuration mode:
Determine which interfaces belong to the same bridge group.
These interfaces will be part of the same spanning tree. This allows the switch router to bridge all nonrouted traffic among the network interfaces comprising the bridge group. Interfaces not participating in a bridge group cannot forward bridged traffic.
If the packet's destination address is known in the bridge table, it is forwarded on a single interface in the bridge group. If the packet's destination is unknown in the bridge table, it is flooded on all forwarding interfaces in the bridge group. The bridge places source addresses in the bridge table as it learns them during the process of bridging.
A separate spanning tree process runs for each configured bridge group. Each bridge group participates in a separate spanning tree. A bridge group establishes a spanning tree based on the BPDUs it receives on only its member interfaces.
Assign a port path cost on the outgoing interface (optional). When configuring POS uplink interfaces and ATM uplink interfaces in conjunction with parallel Gigabit Ethernet links, we recommend that you explicitly assign the port path cost to these interfaces because the default value might not yield the optimal spanning tree.
Troubleshooting Layer 2 Switching
This section describes Layer 2 Switching troubleshooting and includes the following sections:
Figure 12-1 shows the broadcast process all interfaces use to update all the other CAM tables in the bridge group using the following processes:
Each interface is the root of a P2MP VC.
Leaves on all interfaces in the same bridge group are required to flood unknown unicast traffic received on that port.
Broadcasts VC setup when the interface is added to a bridge group.
Each interface is a leaf of point-to-multipoint (P2MP) VCs, with roots on all other interfaces of the bridge group.
Figure 12-1 Layer 2 Switching Broadcasts Used to distribute CAM Updates
Following is the process the switch uses to learn the MAC addresses as show in Figure 12-2:
1. Interface module microcode learns a new MAC Address
2. Interface module microcode sends an IPC to the route processor to update the bridging table
3. Aged entries are removed from the CAM
4. Interface module microcode sends an IPC to the route processor to remove the aged entry from bridging tables
Layer 2 unknown unicast switching is accomplished by the following:
Having all unknown unicast packets sent over the broadcast VC
Depending on the IOS version installed, Layer 2 broadcasts are sent differently:
With Release 12.0(4a)W5(11a) and earlier, Layer 2 broadcasts are sent to the route processor
With Release 12.0(5)W5(13) and later, Layer 2 broadcasts are sent using the P2MP (BCAST) VC only
Note The route processor is not reachable using any of the bridged interfaces. Administrative
tasks to the route processor are preformed using the Console or route processor Ethernet
interface
Figure 12-2 Layer 2 Learning Process
Bridging over Fast EtherChannel
MAC address learning in the switch router occurs differently depending on the IOS version installed.
For Cisco IOS Release 12.0(4a)W5(11a) and earlier, MAC address learning occurs as follows:
The first member of Fast EtherChannel learns the source address via incoming traffic (Egress Learn).
Other members learn the source address (Egress Learn) via IPCs from the Route Processor. These are static entries and will not age out in the CAM.
Static entries are deleted explicitly via IPCs from route processor.
For Cisco IOS Release 12.0(5)W5(13) and later, MAC address learning occurs as follows:
The first member of a Fast EtherChannel learns the source address via Traffic (Egress Learn).
Other members learn the source address (Egress Learn) from the first member, via IPCs over the P2MP VC.
Layer 2 entries age out in the CAM.
Troubleshooting Layer 2 Switching
To troubleshoot a Layer 2 switching problems, use the following commands:
Command
Purpose
show bridge group
Displays bridge group configuration and status information.
show bridge
Displays the status of all the bridge groups on the switch router.
show spanning-tree number
Displays the spanning tree topology for a bridge group.
show interfacesbvi number
Displays BVI interface configuration, status, and statistics. Use this command when the BVI is part of a bridge group.
show interfaces {fastethernet | gigabitethernet} slot/subslot/port (on the ingress interface)
Displays interface configuration, status, and statistics on the ingress interface.
show interfaces {fastethernet | gigabitethernet} slot/subslot/port (on the egress interface)
Displays interface configuration, status, and statistics on the egress interface.
show switch bridge-table entry
Displays bridge table entry summary.
show epc freecam interface {fastethernet | gigabitethernet} slot/subslot/port
Displays information about free space in the content addressable memory.
show epc if-entry interface {fastethernet | gigabitethernet} slot/subslot/portall
Displays all interface entry information for the specific interface.
show epc patricia interface {fastethernet | gigabitethernet} slot/subslot/portmac detail (on the ingress interface)
Displays the MAC patricia tree for the ingress interface.
show epc patricia interface {fastethernet | gigabitethernet} slot/subslot/portmac detail (on the egress interface)
Displays the MAC patricia tree for the egress interface.
As stated before, once the first interface learns a new destination address, source address, and VLAN, that information must be broadcasts to all other interfaces to allow them to update their CAM. That information is broadcast using the Broute VC to communicate with ports on other modules in the same bridge group. Figure 12-3 shows interface Fast Ethernet 0/0/0 using broadcast VC 0 to broadcast an update (to the CAM) to interfaces Fast Ethernet 0/0/1 and 0/0/2.
Figure 12-3 Broadcasting CAM Updates
To confirm that Broute VC 0 is up, use the show atm vc cast p2mp interface fastethernet slot/subslot/port command as shown in the following example.
Switch# show atm vc cast p2mp interface fastethernet 0/0/0
Interface VPI VCI Type X-Interface X-VPI X-VCI Encap Status
FastEthernet0/0/0 0 202 PVC FastEthernet0/0/1 0 227 UP
FastEthernet0/0/2 0 228 UP
Using the cross-connect VCI information from the previous output, confirm that Broute VC 0 is configured on the other interfaces in the bridge group use the show atm vc traffic interface fastethernet slot/subslot/port 0 X-VCI command as shown in the following examples:
Switch# show atm vc traffic interface fastethernet 0/0/0 0 202
Interface VPI VCI Type rx-cell-cnts tx-cell-cnts
FastEthernet 0 202 PVC 0 0
Switch# show atm vc traffic interface fastethernet 0/0/1 0 227
Interface VPI VCI Type rx-cell-cnts tx-cell-cnts
FastEthernet 0 227 PVC 0 0
Switch# show atm vc traffic interface fastethernet 0/0/2 0 228
Interface VPI VCI Type rx-cell-cnts tx-cell-cnts
FastEthernet 0 228 PVC 0 0
Figure 12-4 is an example network of two Layer 2 switches, and is used in the following troubleshooting steps.
Figure 12-4 Layer 2 Troubleshooting Example Network
The following are the processes used to troubleshoot Layer 2 switching connections:
Check the route processor "View" of the spanning tree.
Verify information on interface modules.
Verify VC status between ports.
To troubleshoot Layer 2 switching, perform the following steps:
Step 1 Use the show spanning-tree command to display bridge group information as shown in Figure 12-4.
Switch# show spanning-tree 1
Bridge group 1 is executing the IEEE compatible Spanning Tree protocol
.
(Information Deleted)
.
Port 43 (FastEthernet12/0/1) of Bridge group 1 is forwarding
.
(Information Deleted)
.
Port 58 (GigabitEthernet11/0/1.1 ISL) of Bridge group 1 is forwarding
Step 2 Find the entries in the show spanning-tree command output for the interfaces in question and check the Port fields to confirm the ports at Fast Ethernet12/0/1 and Gigabit Ethernet 11/0/1.1 ISL are forwarding.
Step 3 Use the show bridge command to display bridge group information.
Switch# show bridge 1
.
(Information Deleted)
.
Bridge Group 1:
Address Action Interface
0010.e3aa.aaaa forward Fa12/0/1
0090.21bb.bbbb forward Gi11/0/1.1
Find the entries for those interfaces in the show bridge command output. Note the Address fields to see that the MAC addresses being forwarded to the Fast Ethernet12/0/1 and Gigabit Ethernet 11/0/1.1 ISL connections are in the bridge table. These addresses are used in the following step.
Step 4 Use the show epc mac interface FastEthernet interface command with the MAC address parameter. Add the MAC address being forwarded to interface FastEthernet 12/0/1.
Switch# show epc mac interface FastEthernet 12/0/1 0010.e3aa.aaaa
MACaddr:0010.e3aa.aaaa IF Number:43 MAC Local
Note the IF Number field; in this example, the number is "43." You will need this number in the following command.
Step 5 Use the show epc mac interface GigabitEthernet interface command with the MAC address parameter. Add the MAC address being forwarded to interface GigabitEthernet 11/0/1.1 ISL.
Switch# show epc mac interface FastEthernet 12/0/1 0090.21bb.bbbb
MACaddr:0090.21bb.bbbb IF Number:58
Note the IF Number field; in this example, the number is "58." You will need this number in the following command.
Step 6 Use the show epc patricia interface FastEthernet interface command with the mac detail parameters.
Switch# show epc patricia interface FastEthernet 12/0/1 mac detail
.
(Information Deleted)
.
7# MAC addr:0090.21bb.bbbb IF Number:58 Entry:Remote
Learned 10450 times used
CAM location: 101D
8# MAC addr:0010.e3aa.aaaa IF Number:43 Entry:Local
Learned 0 times used
CAM location: 0FF8
Total number of MAC entries: 8
Step 7 Verify that the information from this command is consistent with the command outputs in Step 5.
If there are inconsistencies or non-zero invalid entries in the tables, you can use the clear bridge command to rebuild the tables.
Step 8 Check the Entry field.
Interface Number 58 has learned of this entry via the flooding from IF Number 42 and it is marked as Remote. Interface number 43 has learned these entries as local entries, which is typical bridge behavior.
Note Entries marked as MyMac are for internal use. These are static entries and are for spanning
tree BPDUs and CDP. The MAC address marked as HSRP is the actual BIA Mac address
of the port. This entry is only present if there is a BVI defined for that bridge group.
Verify that the information from the show epc patricia command output is consistent with the command outputs in Step 4.
If there are inconsistencies or non-zero invalid entries in the tables, you can use the clear bridge command to rebuild the tables.
Caution Use the clear bridge command carefully. It causes a temporary increase in switch router activity which can lead to traffic disruptions.
Step 9 Use the show epc patricia interface GigabitEthernet interface command with the vlan number and details parameters.
Switch# show epc patricia interface GigabitEthernet 11/0/1 vlan 1 detail
15# MAC addr:0090.21bb.bbbb IF Number:58 Entry:Local
Learned 0 times used
CAM location: 1034
16# MAC addr:0010.e3aa.aaaa IF Number:43 Entry:Remote
Learned 6029 times used
CAM location: 101B
Step 10 Check the Entry field. The Entry field descriptions are the same as those in Step 8.
Verify that the information from the show epc patricia command output is consistent with the command outputs in Step 4.
If there are inconsistencies or non-zero invalid entries in the tables, you can use the clear bridge command to rebuild the tables.
Step 11 Use the show epc if-entry interface FastEthernet interface entry GigabitEthernet interface.subinterface command to display the CAM table entry.
Switch# show epc if-entry interface FastEthernet 12/0/1 entry GigabitEthernet 11/0/1.1
IF Entry for GigabitEthernet11/0/1.1 on FastEthernet12/0/1
Mac(hex) - 00:90:21:dd:dd:dd
isMyInteface : False isSubInterface : True
Status Up Broute VC - 662 Bcast VC - 747
Netmask: 32
FEC disabled
ISL, Vlan 1
State : Forwarding
Bridge-Group enabled
IP routing off bridging on
IPX routing off bridging on
Appletalk routing off
In Encapsulation:
ICMP Redirect disabled Unreachable disabled
IP Multicast disabled: ttl-threshold: 0
Step 12 Confirm the following:
Brouter VC status is up.
State is forwarding.
All routing protocols, IP, IPX, and Appletalk are off.
Step 13 Use the same command again but with the interface entries reversed.
Switch# show epc if-entry interface GigabitEthernet 11/0/1.1 entry FastEthernet 12/0/1
IF Entry for FastEthernet12/0/1 on GigabitEthernet11/0/1
Mac(hex) - 00:90:21:cc:cc:cc
isMyInteface : False isSubInterface : False
Status Up Broute VC - 622 Bcast VC - 747
Netmask: 32
FEC disabled
Trunking Disabled
State : Forwarding
Bridge-Group enabled
IP routing off bridging on
IPX routing off bridging on
Appletalk routing off
In Encapsulation:
ICMP Redirect disabled Unreachable disabled
IP Multicast disabled: ttl-threshold: 0
Step 14 Confirm the following:
Brouter VC status is up.
State is forwarding.
All routing protocols, IP, IPX, and Appletalk are off.
Troubleshooting Layer 2 connections differs from troubleshooting Layer 3 connections in the following ways:
MAC entries are learned and not downloaded from route processor.
Not all Ethernet processor interface CAM entries in the same bridge group contain all entries.
You must verify the status of the Broute and the Bcast VC on both the ingress and egress ports.
If you determine the Layer 2 connection is flooding instead of switching, check the following:
If the destination address of the traffic is known:
Check the Layer 2 CAM of the ingress interface for the specific destination address. If the entry exists, then note the destination interface number.
Use the show epc ifmapping command and note the name-string of the interface.
Display the interface table in the ingress interface for the destination interface (obtained from the Layer 2 CAM).
Get the BROUTE VC from the show epc if-entry interface command described earlier.
Use the show atm vc traffic interface interface-namestring0 BROUTE-VC command.
Confirm that the "rx" and "tx" counters are increasing when traffic is switched (by entering the previous command, waiting, and entering the same command again).
If the destination address is unknown:
Use the show epc patricia interface command to display the interface table in the ingress interface for all the interfaces in the bridge-group.
Get the BROUTE VCs from the show epc if-entry interface command described earlier, for all the interfaces in the bridge group.
Use the show atm vc traffic interface interface-namestring0 BROUTE-VC command.
Confirm that the "rx" and "tx" counters are increasing when traffic is switched (by entering the previous command, waiting, and entering the same command again).
Packets are Switched but are Not Appearing on the Wire
If you are sure the packets are being switched but the connection does not appear on the wire, try the following:
Use a Sniffer to see whether they are actually being sent on the wire.
If the packets are not seen by Sniffer, then identify the output interface.
Use the show controller {FastEthernet | GigabitEthernet}card/subcard/port command and check the following:
The MTx and SRx registers for doubts in transmission
The MRx and STx registers for doubts in reception
Layer 2 CAM Display
You might need to check for a specific MAC address on an interface. If so, use the show epc patricia interface {FastEthernet | GigabitEthernet}card/subcard/port mac command. The following is an example with a description of some useful MAC addresses:
Switch# show epc patricia interface fastethernet 0/0/0 mac
1# MAC addr:0000.0000.0000 VC:0 Entry:
2# MAC addr:0900.2b01.0001 MyMAC VC:4 Entry:
3# MAC addr:0180.c200.0000 MyMAC VC:4 Entry:
4# MAC addr:0100.0ccc.cccc MyMAC VC:4 Entry:
5# MAC addr:0010.073d.8207 HsrpMAC VC:4 Entry:
6# MAC addr:0008.e0bc.4190 MyMAC VC:4 Entry:
Total number of MAC entries: 6
In this example check the following:
MAC address 3# and 4# are spanning tree BPDU addresses
MAC address 6# is the interface fastEthernet 0/0/0 Mac-address (IRB only)
Check for Spanning Tree Loop
The spanning-tree algorithm in the IOS software is probably not the source of the spanning tree loop. The spanning-tree loop probably exists because of a problem in the end-to-end connectivity. Try one of the following tests to confirm you do not have a spanning-tree loop:
Use the show epc patricia interface {FastEthernet | GigabitEthernet}card/subcard/port{mac | vlan #} command to confirm the spanning tree multicast address is present in the Layer 2 CAM. See the section "Layer 2 CAM Display" section.
If the spanning tree MAC address is not in the output, then spanning tree is the problem.
Use show spanning-tree bridge-group bridge-group-number command and check for the string "BPDU: sent 0, received 0" in the output. If both switch routers connected with back-to-back interfaces "received 0," then there is a physical layer connectivity problem between the switch routers.
Refer to the Layer 3 Software Feature and Configuration Guide if any changes are necessary to the configuration of the interface.
Layer 2 Bridging Troubleshooting Commands
To troubleshoot a Layer 2 bridging problem, use the following commands:
Command
Purpose
show bridge group
Displays bridge group configuration and status information.
show bridge
Displays the status of all the bridge groups on the switch router.
show spanning-tree number
Displays the spanning tree topology for a bridge group.
show interfacesbvi number
Displays BVI interface configuration, status, and statistics. Use this command when the BVI is part of a bridge group.
show interfaces {fastethernet | gigabitethernet} slot/subslot/port (on the ingress interface)
Displays interface configuration, status, and statistics on the ingress interface.
show interfaces {fastethernet | gigabitethernet} slot/subslot/port (on the egress interface)
Displays interface configuration, status, and statistics on the egress interface.
show switch bridge-table entry
Displays bridge table entry summary.
show epc freecam interface {fastethernet | gigabitethernet} slot/subslot/port
Displays information about free space in the content addressable memory.
show epc if-entry interface {fastethernet | gigabitethernet} slot/subslot/portall
Displays all interface entry information for the specific interface.
show epc patricia interface {fastethernet | gigabitethernet} slot/subslot/portmac detail (on the ingress interface)
Displays the MAC patricia tree for the ingress interface.
show epc patricia interface {fastethernet | gigabitethernet} slot/subslot/portmac detail (on the egress interface)
Displays the MAC patricia tree for the egress interface.
If a BVI is involved, use the following commands:
Command
Purpose
show bridge group
Displays bridge group configuration and status information.
show interfacesirb
Displays integrated routing and bridging configuration and status for all interfaces.
show smf
Displays software MAC address information.
show interfacesbvi number
Displays BVI interface information.
show bridge numbergroup
Displays the status of the member ports in the specified bridge group.
show bridge number
Displays the status of the bridge group.
show epc patricia interface {fastethernet | gigabitethernet} slot/subslot/portmac detail
Displays the MAC patricia tree for the specified interface physical interface in the bridge group with a problem.
Troubleshooting Integrated Routing and Bridging
This section describes troubleshooting Integrated Routing and Bridging (IRB) on the Catalyst 8510 MSR and Catalyst 8540 MSR and Catalyst 8510 CSR and Catalyst 8540 CSR switches.
Your network may require you to bridge local traffic within several segments while having hosts on the bridged segments reach the hosts or routers on routed networks. For example, if you are migrating bridged topologies into routed topologies, you may want to start by connecting some of the bridged segments to the routed networks.
IP Switching with IRB Overview
Using the IRB feature, you can route a given protocol between routed interfaces and bridge groups within a single switch router. Specifically, local or unroutable traffic will be bridged among the bridged interfaces in the same bridge group, while routable traffic will be routed to other routed interfaces or bridge groups.
Because bridging is in the data-link layer (Layer 2) and routing is in the network layer (Layer 3), they have different protocol configuration models. With IP, for example, bridge group interfaces belong to the same network and have a collective IP network address. In contrast, each routed interface represents a distinct network and has its own IP network address. Integrated routing and bridging uses the concept of a Bridge-Group Virtual Interface (BVI) to enable these interfaces to exchange packets for a given protocol.
A BVI is a virtual interface within the campus switch router that acts like a normal routed interface. A BVI does not support bridging, but it actually represents the corresponding bridge group to routed interfaces within the switch router. The interface number is the link between the BVI and the bridge group.
Layer 3 switching software supports the routing of IP and IPX between routed interfaces and bridged interfaces in the same router, in both fast-switching and process-switching paths.
Note BVIs do not support IP multicast routing.
Before Configuring IRB
Consider the following before configuring IRB:
The default route/bridge behavior in a bridge group (when IRB is enabled) is to bridge all packets. Make sure you explicitly configure routing on the BVI for protocols that you want routed.
Packets of nonroutable protocols such as local-area transport (LAT) are always bridged. You cannot disable bridging for the nonroutable traffic.
The protocol attributes should not be configured on the bridged interfaces when using IRB to bridge and route a given protocol. Bridging attributes cannot be configured on the BVI.
A bridge links several network segments into one large, flat network. To bridge a packet coming from a routed interface among the bridged interfaces, the whole bridge group should be represented by one interface.
The BVI has default data-link and network-layer encapsulations. These encapsulations are the same as on the Ethernet, except that you can configure the BVI with some encapsulations that are not supported on a normal Ethernet interface.
Troubleshooting IRB Connections
To troubleshoot the IRB configuration, use the following commands:
Command
Purpose
show interfaces bviinterface-name
Displays BVI information, such as the BVI MAC address and processing statistics.
show interfaces irb
Displays the following BVI information:
Protocols that this bridged interface can route to the other routed interface if this packet is routable
Protocols that this bridged interface bridges
Entries in the software MAC-address filter
Troubleshooting IRB is a combination of both Layer 2 and Layer 3 troubleshooting. Check the following:
When using these processes be aware of the following differences:
Each physical Interface of the Bridge-Group has two MAC Addresses.
BVI MAC Address (same as the first Member of the Bridge-Group)
Physical MAC Address
Packets destined to any of these MAC addresses will be considered for routing.
The CAM must be programmed so the ingress interface can forward frames to a specific egress interface.
High route processor utilization is common when using IRB routing.
Packets get switched by the route processor when the Layer3 (IP or IPX) adjacency gets invalidated in the Layer3 CAM. This is caused by MAC address aging in the Layer 2 CAM.
Follow these steps to troubleshoot the status of an IRB configuration:
Step 1 Use the show interface bvi numbercommand to check the configuration and status of the BVI.
Switch# show interface bvi 1
BVI1 is up, line protocol is up
Hardware is BVI, address is 0000.0ccb.292c (bia 0000.0000.0000)
Ether Channel is a trunking technology that groups together multiple full-duplex 802.3 Ethernet interfaces to provide fault-tolerant, high-speed links between switches, routers, and servers. EtherChannel is a logical aggregation of multiple Ethernet interfaces. EtherChannel forms a single higher bandwidth routing or bridging endpoint. EtherChannel is designed primarily for host-to-switch connectivity or Inter-Switch Link (ISL) switch-to-switch connectivity (for example, connectivity to a Catalyst 5500 switch).
In summary, EtherChannel provides the following benefits:
Logical aggregation of bandwidth
Load balancing
Fault tolerance
The EtherChannel interface (consisting of up to four Ethernet interfaces) is treated as a single interface, which is called a port channel. You must configure EtherChannel on the EtherChannel interface rather than on the individual member Ethernet interfaces. You create the EtherChannel interface by using the interface port-channel interface configuration command. The switch router supports up to 64 port channels.
EtherChannel connections are fully compatible with Cisco IOS VLAN and routing technologies. The ISL VLAN trunking protocol can carry multiple VLANs across an EtherChannel, and routers attached to EtherChannel links can provide full multiprotocol routing with support for host standby using Host Standby Router Protocol (HSRP).
Your switch router supports Fast EtherChannel (FEC) and Gigabit EtherChannel (GEC).
Cisco Fast EtherChannel technology builds upon standards-based 802.3 full-duplex Fast Ethernet to provide a reliable high-speed solution for the campus network backbone. Fast EtherChannel provides bandwidth scalability within the campus by providing increments of 200 Mbps to 800 Mbps.
Cisco Gigabit EtherChannel technology provides bandwidth scalability within the campus by providing increments of 2 Gbps to 8 Gbps.
Note EtherChannel does not support IP/IPX filtering at Layer 3 with the ACL daughter card.
Note For more detailed information about EtherChannel, refer to the
"Configuring LAN Interfaces" chapter in the
C isco IOS Interface Configuration Guide.
Troubleshooting Bridging Over Fast EtherChannel
To troubleshoot the EtherChannel status and configuration, use the following commands:
Command
Purpose
show interfaces port-channel number
Displays the status of the physical interface.
show epc fe-channel interface {fastethernet | gigabitethernet} slot/subslot/port channel port-channel number
Displays all EPC interface information for the specific interface and port channel.
show epc if-entry interface {fastethernet | gigabitethernet} slot/subslot/port entry port-channelnumber
Displays interface entry information for the specific interface.
Follow these steps to troubleshoot the EtherChannel status and configuration:
Step 1 Use the show interfaces port-channel number command to confirm the EtherChannel status and configuration.
Switch# show interfaces port-channel 1
Port-channel1 is up, line protocol is up
Hardware is FEChannel, address is 0010.073c.0513 (bia 0000.0000.0000)
MTU 1500 bytes, BW 300000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Unknown duplex, Unknown Speed
ARP type: ARPA, ARP Timeout 04:00:00
No. of active members in this channel: 3
Member 0 : FastEthernet1/0/4 , Full-duplex, 100Mb/s
Member 1 : FastEthernet1/0/6 , Full-duplex, 100Mb/s
Member 2 : FastEthernet1/0/7 , Full-duplex, 100Mb/s
Last input 00:00:00, output never, output hang never
0 output buffer failures, 0 output buffers swapped out
Switch#
Step 2 Check the Port-channel field. It should indicate up.
Step 3 Note the MAC address assigned to the port channel. It will be used in Step 4.
Step 4 Use the show epc if-entry interface command with the entry interface parameters to display the status of the Broute VCs.
Switch# show epc if-entry interface fastEthernet 1/0/4 entry port-channel 1
IF Entry for Port-channel1 on FastEthernet1/0/4
Mac(hex) - 00:10:07:3C:05:13
isMyInteface : True isSubInterface : False
Status Up Broute VC - 97 Bcast VC - 0
Netmask: 32
FEC enabled ( Flow-based Load-balancing )
Trunking Enabled
State : Not-Applicable/Listening/Blocking
Bridge-Group disabled
IP routing off bridging off
IPX routing off bridging off
Appletalk routing off
In Encapsulation:
ICMP Redirect enabled Unreachable enabled
IP Multicast disabled: ttl-threshold: 0
ACL Indexs:
Input ACL: 0 Output ACL: 0
ACL Flags:
Input IP: OFF Output IP: OFF
Input IPX: OFF Output IPX: OFF
Switch#
Step 5 Confirm that the MAC address in this step matches the MAC address displayed in Step 1.
For inconsistencies between the adjacency table and the EPC IP address table, use the clear arp or clear adjacencies command to rebuild the tables. When you use these commands, the router will send an ARP request for all entries in the ARP cache. As replies come back, it will refresh the cache. If any entries time out, they will be cleared from the table. The router will then build the adjacency table using this information, and populate the interface EPC IP address table.
Step 6 Use the show epc if-entry interface command with the entry interface parameters to display the status of the VCs.
Switch# show epc fe-channel interface fastEthernet 1/0/4 channel port-channel 1
FEC Group (Port-channel1) Information on FastEthernet1/0/4