I have a communication problem between 3 switches and I have really need advise to solve the problem
The communication disconnect frequently (every 2-3 min for 10-15 sec)
I think the problem originate from main 3560 switch because the communication interrupt both other two switches that come from main switch
The problem is weird because I can solve the problem temporary by use simple 4 port switch between two Cisco switch and communication established without interrupt
Topology very simple like below
3 rd 2960 switch --------------Main 3560 switch-------------------- 2nd 3560 switch
Temporary solution without vlans
3 rd 2960 switch ---------simple hub (4 port)-----------Main 3560 switch----------simple hub (4 port)---------- 2nd 3560 switch
Main Switch and 3 rd 3560 switch Trunk config example
interface GigabitEthernet0/20
switchport trunk encapsulation dot1q
switchport trunk native vlan 10
switchport mode trunk
switchport nonegotiate
2960 switch example
interface GigabitEthernet1/0/48
switchport trunk native vlan 10
switchport mode trunk
switchport nonegotiate
Trunk port interface
MainSwitch#sh int gi0/20
GigabitEthernet0/20 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is b0fa.eb7e.1c14 (bia b0fa.eb7e.1c14)
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:54, output 00:00:04, 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: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 2000 bits/sec, 3 packets/sec
703255 packets input, 104881192 bytes, 0 no buffer
Received 608879 broadcasts (581903 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 581903 multicast, 0 pause input
0 input packets with dribble condition detected
2843929 packets output, 288502274 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
231 unknown protocol drops
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
What I tried to determine the problem;
- There is no physical redundant connection even so first I made main switch spanning-tree vlan 1-4094 priority 24576 and other spanning-tree vlan 1-4094 priority 28672 and spanning-tree vlan 1-4094 priority 32768 on top of that I use the command no spanning-tree vlan 1-4094 for 3 switches so that the be unaffected spanning-tree issue
- I used simple 4 port switch (like hub) between 2 cisco switch by change trunk port to access port. Yes communication was established without interrupt but I can only used one vlan. And No one wants to use simple switch between two Cisco switch
- I tried 3 different cat 6 cable to determine physical connection problem but result was same Actually I have already two connection problem come from main switch to other two and sh interface command reliability is 255/255 there is no bad physical connection certainly
- I change vtp mode off for 3 switch
- I change trunk port to access port switches connection for 1 vlan connection but result was same, disconnect issue went on frequently
- I closed all port of the 2960 switch except trunk port to be unaffected end devices and I tried to pint vlan ip and disconnect issue went on frequently
- I check cpu usage but there is no meaningful a peak
- I removed the command below trunk ports storm-control broadcast level 3.00
storm-control multicast level 3.00
storm-control action shutdown
storm-control action trap
- I have also tried to change speed trunk port gigabit to 100 mb/s
