This document discusses and provides a sample configuration of Fast EtherChannel (FEC) and 802.1Q trunking, between a Catalyst 2948G-L3 switch that runs Cisco IOS® software and switches that run CatalystOS (all models, including Catalyst 4000, 5000, and 6000 series switches).
For a list of Catalyst switches that support 802.1Q and ISL trunking encapsulations, refer to System Requirements to Implement Trunking.
There are certain guidelines for the configuration of EtherChannel and trunking. Refer to the documentation for your switch software. For example, if you are running CatalystOS (CatOS) software release 8.2.x on a Catalyst 6500/6000, refer to the Catalyst 6500 Series Software Configuration Guide, 8.2 and carefully examine any configuration guidelines and restrictions in the Configuring Ethernet VLAN Trunks and Configuring EtherChannel sections.
The information in this document is based on these software and hardware versions:
Catalyst 2948G with CatOS 7.1.2 installed (802.1Q only)
Catalyst 2948G-L3 with Cisco IOS Software Release 12.0(14)W5(20) installed
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
For more information on document conventions, refer to the Cisco Technical Tips Conventions.
The use of EtherChannel can provide increased bandwidth and redundancy. EtherChannel is convenient because it scales the bandwidth without any increase in the complexity of the design. Spanning-tree treats the EtherChannel bundle as a single link, so no loops are introduced. Routing protocols also treat the EtherChannel as a single routed interface with a common IP address. EtherChannel bundling provides up to 1600 Mbps FEC (Fast EtherChannel), full duplex, or 16 Gbps Gigabit EtherChannel (GEC). Trunking carries traffic from several VLANs over a point-to-point link between the two devices. Two methods of trunking are Inter-Switch Link Protocol (ISL, a Cisco-proprietary protocol) or 802.1Q (an IEEE standard). This document specifically deals with 802.1Q trunking.
In this section, the configurations presented will include a four-port FEC and 802.1Q trunk between the 2948G-L3 and a CatOS switch.
Note: To find additional information about the commands in this document, use the Command Lookup Tool (registered customers only) .
This document uses this network setup:
This document uses these configurations:
Catalyst 2948G |
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CatOS (enable) show config This command shows non-default configurations only. Use 'show config all' to show both default and non-default configurations. ............ ....................... .. begin ! # ***** NON-DEFAULT CONFIGURATION ***** ! ! #time: Thu Nov 21 2002, 15:24:27 ! #version 7.1(2) ! ! #system web interface version(s) set prompt CatOS ! #test ! #frame distribution method set port channel all distribution mac both ! #ip set interface sc0 1 10.10.10.1/255.255.255.0 10.10.10.255 set interface sl0 down set interface me1 down set ip alias default 0.0.0.0 set ip alias cat 10.10.10.2 ! #spantree #vlan <VlanID> ! #set boot command set boot config-register 0x2102 clear boot system all ! !--- Ports 2/1 to 2/4 are assigned to a port channel. #port channel set port channel 2/1-4 29 ! #multicast filter set igmp filter disable ! #module 1 : 0-port Switching Supervisor ! !--- The trunking mode is specified as 802.1Q, because it !--- is the only encapsulation that is supported on the !--- 2948G. The mode is set to nonegotiate, because the !--- 2948G-L3 does not support Dynamic Trunking Protocol (DTP). #module 2 : 50-port 10/100/1000 Ethernet set trunk 2/1 nonegotiate 802.1Q 1-1005 set trunk 2/2 nonegotiate 802.1Q 1-1005 set trunk 2/3 nonegotiate 802.1Q 1-1005 set trunk 2/4 nonegotiate 802.1Q 1-1005 !--- The channel mode is set to on, because 2948G-L3 !--- does not support Port Aggregation Protocol (PAgP). set port channel 2/1-4 mode on end |
Catalyst 2948G-L3 |
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2948G-L3# show run Building configuration... Current configuration: ! version 12.0 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname 2948G-L3 ! enable secret 5 $1$bNvR$33puy1WCyrdKMvlnj61Js. ! ip subnet-zero ! ! !--- The logical port-channel interface must be created !--- before you put the physical interfaces into the !--- channel group.interface port-channel1. no ip address no ip directed-broadcast hold-queue 300 in ! !--- Specify the native VLAN: VLAN 1 in this example, !--- which is the default. For performance and security !--- reasons, it is recommended that you keep the user !--- traffic off of the native or management VLAN. interface Port-channel1.1 encapsulation 802.1Q 1 native ip address 10.10.10.2 255.255.255.0 no ip redirects no ip directed-broadcast ! interface Port-channel1.2 encapsulation 802.1Q 2 ip address 10.10.11.2 255.255.255.0 no ip directed-broadcast ! !--- Specify all of the physical ports that are part !--- of the logical port channel interface. interface FastEthernet1 no ip address no ip directed-broadcast channel-group 1 ! interface FastEthernet2 no ip address no ip directed-broadcast channel-group 1 ! interface FastEthernet3 no ip address no ip directed-broadcast channel-group 1 ! interface FastEthernet4 no ip address no ip directed-broadcast channel-group 1 ! !--- Output suppressed. ! ip classless ! ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end |
This section provides information to confirm that your configuration is working properly.
show port channel—Displays EtherChannel information. It also displays the load-balance or frame-distribution scheme, port, and port-channel information.
!--- Verify that the port channel is UP (connected, on) and that !--- all the physical ports are members (channel ID). CatOS (enable) show port channel Port Status Channel Admin Ch Mode Group Id ----- ---------- -------------------- ----- ----- 2/1 connected on 29 801 2/2 connected on 29 801 2/3 connected on 29 801 2/4 connected on 29 801 Port Device-ID Port-ID Platform ----- ------------------------------- ---------------------- -------------- 2/1 2948G-L3 FastEthernet1 cisco Cat2948G 2/2 Not directly connected to switch 2/3 2948G-L3 FastEthernet3 cisco Cat2948G 2/4 2948G-L3 FastEthernet4 cisco Cat2948G
Note: It is quite normal for port 2/2 not to be directly connected to the switch. Output of the show port channel command on the switch that is connected to a router normally looks like this example. Because the router does not participate in PAgP (used to negotiate channels) and the channeling is on, the ports show the FEC neighbor information using Cisco Discovery Protocol (CDP) data. Cisco IOS software sends out CDP packets on both the channel interface and the physical interfaces. One of the Catalyst ports sees multiple CDP neighbors and reports not directly connected to switch. This is a cosmetic issue, and more information is available in Cisco Bug ID CSCdp04017 (registered customers only) .
show port channel statistics—Displays the Admin Group of the port channel and displays whether PAgP is in use on the port channel.
Verify that PAgP is not in use on the links.
CatOS (enable) show port channel status Port Admin PAgP Pkts PAgP Pkts PAgP Pkts PAgP Pkts PAgP Pkts PAgP Pkts Group Transmitted Received InFlush RetnFlush OutFlush InError ----- ------- ----------- --------- --------- --------- --------- --------- 2/1 29 0 0 0 0 0 0 2/2 29 0 0 0 0 0 0 2/3 29 0 0 0 0 0 0 2/4 29 0 0 0 0 0 0
show trunk—Displays the the trunking mode, encapsulation, and native VLAN.
Verify that trunking is enabled on the physical interfaces and on the port channel interface. Also, verify that the trunking mode is correctly set to nonegotiate.
Note: On a 802.1Q trunk, the native VLAN must match on both sides.
CatOS (enable) show trunk * - indicates vtp domain mismatch Port Mode Encapsulation Status Native vlan -------- ----------- ------------- ------------ ----------- 2/1 nonegotiate 802.1Q trunking 1 2/2 nonegotiate 802.1Q trunking 1 2/3 nonegotiate 802.1Q trunking 1 2/4 nonegotiate 802.1Q trunking 1 Port Vlans allowed on trunk -------- ----------------------------------------------------------------- 2/1 1-1005 2/2 1-1005 2/3 1-1005 2/4 1-1005 Port Vlans allowed and active in management domain -------- ----------------------------------------------------------------- 2/1 1 2/2 1 2/3 1 2/4 1 Port Vlans in spanning tree forwarding state and not pruned -------- ----------------------------------------------------------------- 2/1 1 2/2 1 2/3 1 2/4 1
show interfaces port-channel 1—Provides the status of the port channel and the ports that are a member of the port channel group.
Verify that all of the physical interfaces that are a part of the EtherChannel can be seen as members.
2948G-L3# show interfaces port-channel 1 Port-channel1 is up, line protocol is up Hardware is FEChannel, address is 0008.a308.1c07 (bia 0000.0000.0000) MTU 1500 bytes, BW 400000 Kbit, DLY 100 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) Half-duplex, Unknown Speed, Media type unknown ARP type: ARPA, ARP Timeout 04:00:00 No. of active members in this channel: 4 Member 0 : FastEthernet2 Member 1 : FastEthernet1 Member 2 : FastEthernet4 Member 3 : FastEthernet3 Last input 00:00:00, output 00:00:55, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/300, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 596128 packets input, 50714549 bytes, 0 no buffer Received 7 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 watchdog, 0 multicast 0 input packets with dribble condition detected 44294 packets output, 17498215 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
show cdp neighbor—Lists all of the directly connected Cisco devices that are discovered through CDP.
Verify that the switch on the other end is visible through all physical ports.
2948G-L3# show cdp neighbor Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater Device ID Local Intrfce Holdtme Capability Platform Port ID JAB032400H2 Port-channel1.1 126 T S WS-C2948 2/3 JAB032400H2 Port-channel1.1 124 T S WS-C2948 2/4 JAB032400H2 Port-channel1.1 123 T S WS-C2948 2/1 JAB032400H2 Port-channel1.1 123 T S WS-C2948 2/2
There is currently no specific troubleshooting information available for this configuration.