07-11-2012 10:43 AM - edited 03-07-2019 07:43 AM
Hi all, I have 4 switches (2 x 2960 & 2 x 3500) connected together in 1 big loop (1 to 2 to 3 to 4) using fibre on the gigabit interface ports. My question relates to spanning-tree.
Switch 1 is the root bridge. Between switch 1 and switch4 i cannot establish lights on the interfaces g 0/1 (these interfaces are directly connected with fibre). Below is the output from both switches:-
switch1#show spanning-tree interface g 0/1
no spanning tree info available for GigabitEthernet0/1
switch4#
Interface Gi0/1 (port 40) in Spanning tree 1 is down
Port path cost 4, Port priority 128
Designated root has priority 24577, address d824.bd16.b500
Designated bridge has priority 32768, address 0006.2828.d180
Designated port is 40, path cost 12
Timers: message age 0, forward delay 0, hold 0
BPDU: sent 3, received 667
I would have thought one interface (int g 0/1 on switch 1 or switch4) would be in block status and the other remaining interface to be in fwd status. However as you can see from the above output there is no spanning-tree info available on switch1. On switch4 the interface is showing as down, which indicates there is no physical connection? I have replaced the fibre lead and the gbic modules in sw1 & sw4.
The result here is I have no redundant link (there is already a break between switch1 & switch4 becuase of this issue)
Can anyone shed any light on this please
07-11-2012 12:44 PM
Hi Shane,
I dont exactly know how to solve your problem, just wondering - if SW1 is root and is directly connected to SW4, you should expect Gi0/1 on SW1 to be designated - FWD state, but at SW4 Gi0/1 will be root port, so in FWD state too (not blocked). Correct me somebody if I am wrong.
Have you tried to change fiber to classical cross-over cable? Maybe it would also help to look in output of show int gi0/1 at both switches while they are connected and expected to work. Do these interterfaces work well in general?
Best Regards
Jan Janovic
07-11-2012 02:41 PM
Thanks for the reply Jan. I have checked the interfaces g 0/1 on switch1 and also switch4 as suggested, both are showing as down. I have replaced switch4, replaced the fibre connecting switch 1 and switch4 and replaced both gbics used on the interfaces g 0/1 of switch 1 & switch4. Interface g 0/2 on switch1 (connected to switch2) is DESG fwd.
07-11-2012 03:26 PM
Hello Shane,
Jan is heading in the correct direction - the up/down status of your ports is something that precedes STP, and is related to basic Layer1/Layer2 connectivity. If your ports are reported as down then they basically tell you they are disconnected - not blocked by STP.
Can you please post the complete output of the following commands from both Sw1 and Sw4?
Thank you!
Best regards,
Peter
07-11-2012 10:53 PM
Hello Peter, thanks for the reply. Please see below the outputs of sw1 and sw4 as suggested. On sw4 (3500xl) the cmd "show interface gi0/1 capabilities" is not allowed
SWITCH1#show interface gi0/1
GigabitEthernet0/1 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is d824.bd16.b519 (bia d824.bd16.b519)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Auto-duplex, Auto-speed, link type is auto, media type is 1000BaseSX SFP
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 21w6d, output 21w6d, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
66734 packets input, 12311737 bytes, 0 no buffer
Received 3894 broadcasts (1799 multicasts)
14 runts, 0 giants, 0 throttles
14 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1799 multicast, 0 pause input
0 input packets with dribble condition detected
168878 packets output, 42300964 bytes, 0 underruns
0 output errors, 0 collisions, 1 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
SWITCH1#show interface status | inc Gi0/1
Gi0/1 notconnect 1 auto auto 1000BaseSX SFP
SWITCH1#show interface gi0/1 capabilities
GigabitEthernet0/1
Model: WS-C2960-24PC-L
Type: 1000BaseSX SFP
Speed: 1000
Duplex: full
Trunk encap. type: 802.1Q
Trunk mode: on,off,desirable,nonegotiate
Channel: yes
Broadcast suppression: percentage(0-100)
Flowcontrol: rx-(off,on,desired),tx-(none)
Fast Start: yes
QoS scheduling: rx-(not configurable on per port basis),
tx-(4q3t) (3t: Two configurable values and one fixed.)
CoS rewrite: yes
ToS rewrite: yes
UDLD: yes
Inline power: no
SPAN: source/destination
PortSecure: yes
Dot1x: yes
Multiple Media Types: rj45, sfp, auto-select
SWITCH1#show run int gi0/1
Building configuration...
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
switch4#show interface gi0/1
GigabitEthernet0/1 is down, line protocol is down
Hardware is Gigabit Ethernet, address is 0006.2828.d199 (bia 0006.2828.d199)
MTU 1500 bytes, BW 0 Kbit, DLY 0 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Auto-duplex , 1000Mb/s, media type is SX
output flow-control is off, input flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 16:19:14, output 16:19:59, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 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
2584 packets input, 309915 bytes, 0 no buffer
Received 2536 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1702 multicast, 0 pause input
68 packets output, 12336 bytes, 0 underruns
0 output errors, 0 collisions, 1 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
switch4#show interface status | inc Gi0/1
Gi0/1 notconnect 1 Auto 1000 1000BASESX
switch4#show interface gi0/1 capabilities
^
% Invalid input detected at '^' marker.
switch4#show interface gi0/1 ?
accounting Show interface accounting
crb Show interface routing/bridging info
ethernet Show ethernet vlan type
fair-queue Show interface Weighted Fair Queueing (WFQ) info
flow-control Show flow control information
irb Show interface routing/bridging info
link-trap Show interface traps on no link
mac-accounting Show interface MAC accounting info
precedence Show interface precedence accounting info
pruning Show interface pruning information
random-detect Show interface Weighted Random Early Detection (WRED) info
rate-limit Show interface rate-limit info
status Show interface line status
switchport L2 interface information
trbrf Show BRF tokenring vlan type
type Show vlan types
| Output modifiers
switch4#show run int gi0/1
Building configuration...
Current configuration:
!
interface GigabitEthernet0/1
end
07-11-2012 11:16 PM
Hello Shane,
Thank you for the reply. The output you have posted suggests that there is a basic connectivity problem between your two switches.
The most natural question is whether the fiber and the optical GBICs/SFPs are okay and properly matched. Are you able to verify that each GBIC/SFP is capable of linking up successfully with some other GBIC/SFP that is proved to work? If these modules are using two fibers, you could make a test with looping the GBIC/SFP by interconnecting its Tx and Rx port, however, I recommend caution here - a longer fiber or an attenuator is recommended in order not to overload the Rx detector.
Also, the 1000BaseSX needs multimode fiber to be used - I assume you are using the proper fiber type.
Best regards,
Peter
07-12-2012 10:23 AM
Hi Paul
If I swap the 'suspect' fibre, gbic & sfp between sw1 & sw4 with the 'working' fibre, gbic & sfp between sw2 & sw3, the fault remains between sw1 & sw4. The connection between sw2 & sw3 becomes active. This proves there is no fault with the fibre, gbic or sfp. I agree there is a basic layer1 / 2 connectivity issue from the output of the interfaces however I believe I have confimed all hw as working. I will do further testing and keep you updated. Thanks for your help so far
07-12-2012 11:30 AM
Hello Shane,
You're welcome but the "thank you" you gave me is not deserved yet.
As the fault seems to be stuck between Sw1 and Sw4, I am starting to wonder if the SFP/GBIC slot itself (not the transceiver but rather the socket) on either of these switches is working properly. Would either of Sw1/Sw4 Gi0/1 ports come up if it was connected to a different and guaranteedly working fiber port/transceiver? Try to avoid interconnecting Sw1 and Sw4 Gi0/1-s in particular.
Also, can you try using the media-type sfp on the 2960 Gi0/1 port? Are you using genuine Cisco SFP/GBIC?
Best regards,
Peter
07-14-2012 09:14 AM
Can you provide the running config for both swithces? All that is needed the the config for the interface on switch 1 connected to switch 4 and the config for the interface on swich 4 connect to switch one.
Regards,
Sebastian
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