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ISL and Dot 1 q trunk causing input and crc errors

mahesh18
Frequent Contributor
Frequent Contributor

Hi all,

i have two switches and i have trunk connection between them .

switch 1

3548XL#sh int fa0/9
FastEthernet0/9 is up, line protocol is up
  Hardware is Fast Ethernet, address is 0003.6b7b.5a09 (bia 0003.6b7b.5a09)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 128/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 100Mb/s, 100BaseTX/FX
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 13:53:36, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:00:53
  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 1000 bits/sec, 3 packets/sec
     0 packets input, 7755 bytes
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     108 input errors, 108 CRC, 0 frame, 0 overrun, 0 ignored*************************************
     0 watchdog, 0 multicast
     0 input packets with dribble condition detected
     150 packets output, 10502 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
3548XL#  sh run int fa0/9
Building configuration...

Current configuration:
!
interface FastEthernet0/9
duplex full
speed 100
switchport mode trunk
end

3548XL#sh int fa0/9 swi
3548XL#sh int fa0/9 switchport
Name: Fa0/9
Switchport: Enabled
Administrative mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: isl ******************************************
Operational Trunking Encapsulation: isl
Negotiation of Trunking: Disabled
Access Mode VLAN: 0 ((Inactive))
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: 1,10,20,30
Pruning VLANs Enabled: 2-1001

Priority for untagged frames: 0
Override vlan tag priority: FALSE
Voice VLAN: none
Appliance trust: none
Self Loopback: No

--Switch A shows ISL  trunk and input and crc errors on port fa0/9

Switch B

2950T#                      sh int fa0/5
FastEthernet0/5 is up, line protocol is up (connected)
  Hardware is Fast Ethernet, address is 000b.bece.bbc5 (bia 000b.bece.bbc5)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Half-duplex, 100Mb/s, media type is 100BaseTX
  input flow-control is unsupported output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 14:01:30, output 00:00:01, 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 2000 bits/sec, 3 packets/sec
  5 minute output rate 1000 bits/sec, 2 packets/sec
     174610 packets input, 16877016 bytes, 0 no buffer
     Received 174608 broadcasts (174608 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 174608 multicast, 0 pause input
     0 input packets with dribble condition detected
     119330 packets output, 8508389 bytes, 0 underruns
     0 output errors, 0 collisions, 2 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
2950T# sh run int fa0/5
Building configuration...

Current configuration : 56 bytes
!
interface FastEthernet0/5
switchport mode trunk
end

2950T#                      sh int fa0/5 swi
2950T#                      sh int fa0/5 switchport
Name: Fa0/5
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

--- As you can see that both switches have trunk mismatch.

my question is why trunk mismatch type creates errors  on on side of switch port and not another.

--as we can see that ISL type trunk port has errors while dot1 q have not why?

thanks

mahesh

8 Replies 8

sudkulka
Cisco Employee
Cisco Employee

Besides trunking mismatch, you have duplex mismatch on both ends. You could try the following

- match duplex ( either allow auto neogtiation on both sides or configure duplex full on both ports)

If errors continue, then on 2950 configure "dot1q tag native" globally as a test.

Regards,

Sudha

mahesh18
Frequent Contributor
Frequent Contributor

Hi,

i fix the duplex mismatch

errors still continue

and command

2950T(config)#int fa0/5
2950T(config-if)#dot1q tag native
                     ^
% Invalid input detected at '^' marker.

does not work

thanks

mahesh

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

as we can see that ISL type trunk port has errors while dot1 q have not why?

It's because the one that has line errors is a 3500XL and the one that doesn't is a 2950.  The 2900/3500XL switches are the first generation of "modern" switches but they are a basket-case when it comes to auto-negotiation of speed and duplex.  Change the speed and duplex settings to auto and see if it goes well but DO NOT reboot the 3500XL switch because the result will not be the same every time.

mahesh18
Frequent Contributor
Frequent Contributor

Hi,

thanks for reply

i hardocded both sides and errors are incrementing.

i will test with auto and keep you posted

mahesh18
Frequent Contributor
Frequent Contributor

Hi leolaohoo

thanks for reply.

i did auto at both ends and both ends show auto   --- speed  100 and   duplex full.

still i can see errors on 3548xl. also i clear counters and errors are incrementing.

Hi,

Wanted to add few points, CRC means the checksum on receiving side is not matching with the one sent from source side meaning either data has gone corrupted while in transmission or the sending side sent bad data. This can happen due to bad cable, if there is any interference near the wire (copper) etc.

So, I will suggest

--Make sure speed/duplex matches which you already mentioned, make both ends to have same encapsulation (unless it is not possible).

--Make sure cable is fine, if possible try replacing it if you have not done that already.

--If above two doesn't help you then check what is the behavior if you change port on switch, make port as access port or if you connect a PC to the port.

If we have duplex mismatch then it cause collisions because half-duplex side thinks that it should not receive data while it is transmitting and full-duplex side can transmit/receive both at same time.

I hope this will help you in solving your problem or at least will give you directions.

-Shahid

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

Right.  If it's auto-full, auto-100 in the 3500XL, then make sure it's the same thing on the 2950.  Unfortunately, you'll need to constantly check both sides for speed and duplex settings.

mahesh18
Frequent Contributor
Frequent Contributor

hi,

thanks for reply.

i check both sides are set to auto auto and they are set to full duplex 100 .

duplex settings do not change.

thanks

mahesh

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