Re: Trunk port not working between C3850 and C3560X - Page 2

RookieNet55 · ‎12-24-2023

Hi everyone,

I have C3560X switch which is the current core, trying to add a new switch C3850-24XS via the trunk port. The link status is up, I can see the lights on both ports physically. But no communication between the switches via trunk port, no CDP neighbours either. There is VTP on both switches, C3560X is server and C3850 is configured as client, I have double checked the passwords and they are good.

Any help is appreciated on getting this trunk up and running. I can provide more config info as required.

Below are some configurations.

C3560X side

ip routing

interface Vlan100
description Management VLAN
ip address 172.18.100.1 255.255.255.0

interface GigabitEthernet0/24
switchport trunk encapsulation dot1q
switchport trunk native vlan 100
switchport trunk allowed vlan 100
switchport mode trunk

sh int gi0/24 status

Port Name Status Vlan Duplex Speed Type
Gi0/24 new san test connected trunk a-full a-1000 10/100/1000BaseTX

VTP Version                     : running VTP2
Configuration Revision          : 17
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 15
VTP Operating Mode              : Server
VTP Domain Name                 : CDCCORPVTP1
VTP Pruning Mode                : Disabled
VTP V2 Mode                     : Enabled
VTP Traps Generation            : Disabled
MD5 digest                      : 0x89 0x03 0xC4 0x18 0xAD 0x3D 0xAD 0xB3
Configuration last modified by 0.0.0.0 at 3-1-93 00:20:35
Local updater ID is 172.18.2.1 on interface Vl2 (lowest numbered VLAN interface found)

C3850 side

ip routing

interface Vlan100
ip address 172.18.100.9 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 172.18.100.1

interface TenGigabitEthernet1/0/24
switchport trunk native vlan 100
switchport trunk allowed vlan 100
switchport mode trunk

sh int te1/0/24 status

Port Name Status Vlan Duplex Speed Type
Te1/0/24 connected trunk a-full a-1000 10/100/1000BaseTX SFP

sh vtp status
VTP Version capable             : 1 to 3
VTP version running             : 2
VTP Domain Name                 : CDCCORPVTP1
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Disabled
Device ID                       : 0056.2bd9.1e80
Configuration last modified by 172.18.100.9 at 12-21-23 21:55:55

Feature VLAN:
--------------
VTP Operating Mode                : Client
Maximum VLANs supported locally   : 1005
Number of existing VLANs          : 7
Configuration Revision            : 0
MD5 digest                        : 0xB3 0x4C 0x27 0x65 0xCD 0x6D 0x7D 0x1C
                                    0xAF 0x5B 0x02 0x3A 0x60 0x47 0xA0 0xAF

balaji.bandi · ‎12-26-2023

This looks strange and buzzard for me totally- never come across these kind of issue before (until we are hitting any one of the side bugs ?)

My guesses will be :

1. Due to old code in 3650 may be ?

2. Try speed strict to speed 1000 or no speed negotiation - options

3. I also connect PC directly to port and configure the IP and test both the side you able to ping - the switch to be sure the ports are working (nothing weird going on)

4. you can also making layer 3 interface and test it. (i have suggested other post config)

On 3850 Try debugging see you can find any information : use below STP troubleshooting guide :

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/28943-170.html

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RookieNet55 · ‎12-27-2023

Here is what I tried to test the most basic item. I defaulted the config on both these interfaces on respective switches and then checked the CDP neighbours that doesn't show up anything.

CDP neighbours should still show up when there is physical connectivity between the links right ?
I am now suspecting the SFP, the SFP used in my case is "SFP-GE-T" on C3850 side, but no SFP on C3560 because that is just a regular gigabit RJ45 port switch. Also this SFP is officially supported for C3850-24XS but still running into this weird issue.

I will be onsite to test with more SFP's just in case and keep you posted. Sincere thanks for taking time to looking into my issue.

RookieNet55 · ‎12-27-2023

I made an access port on the switch, with vlan 100. The SVI of vlan 100 was 172.18.100.9 255.255.255.0

Ip routing was disabled on this switch.

Tried to connect the laptop and configured the ethernet to be on 172.18.100.55 255.255.255.0 , no gateway and no dns. It is a windows 10 laptop.

And no luck with ping to SVI via the access port. Swapped the SFP's and the cable

RookieNet55 · ‎12-27-2023

So it was indeed the SFP problem. I have was using Startech GLC-T compatible SFP's atleast what is said on the 10pk box, but on the SFP's itself the label was GLC-TST. And on reading the SFP in the switch it was showing up as SFP-GE-T. This SFP-GE-T says it is compatible on cisco compatibility matrix for C3850-24XS

Then I tried an old SFP that was lying around which said GLC-T on physical SFP module, but on reading in the switch it doesn't say the model name. But that worked on C3850's.

A bit confused at the moment.

Leo Laohoo · ‎12-25-2023

@RookieNet55 wrote:

  Last input never, output 00:00:01, output hang never
     0 packets input, 0 bytes, 0 no buffer

If the ports are not trunk, does it work?

RookieNet55 · ‎12-25-2023

You mean to say I switch to access ports on both ends and test ?

Leo Laohoo · ‎12-25-2023

Yes.

And use Gi ports and not Ten port.

RookieNet55 · ‎12-25-2023

I tried setting both as access ports

switchport mode access

switchport access vlan 100

Above is the config on both ports of the both the switches. Ping doesn't work to either switches SVI vlan 100 ip's.

Regarding the Tengigabit port, I don't see the gigabit version of the same port when I run "sh ip int br", though the sfp is used is a 1gig copper

Leo Laohoo · ‎12-25-2023

Can we see the "sh interface" of the output from the 3850?

RookieNet55 · ‎12-26-2023

sh interface te1/0/24

TenGigabitEthernet1/0/24 is up, line protocol is up (connected)
  Hardware is Ten Gigabit Ethernet, address is 0056.2bd9.1e98 (bia 0056.2bd9.1e98)
  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 not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX SFP
  input flow-control is on, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/2000/0/0 (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 1000 bits/sec, 1 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     47196 packets output, 3724370 bytes, 0 underruns
     Output 3893 broadcasts (0 multicasts)
     0 output errors, 0 collisions, 5 interface resets
     0 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

MHM Cisco World · ‎12-25-2023

Show interface trunk

Show stp in both SW for vlan 100

Show interface status

MHM

RookieNet55 · ‎12-26-2023

Important thing is no cdp neighbours
sh interface trunk on C3850

sh int trunk

Port        Mode             Encapsulation  Status        Native vlan
Te1/0/24    on               802.1q         trunking      100

Port        Vlans allowed on trunk
Te1/0/24    1-4094

Port        Vlans allowed and active in management domain
Te1/0/24    1,100

Port        Vlans in spanning tree forwarding state and not pruned
Te1/0/24    1,100

STP vlan 100 on C3560 and interface status

VLAN0100
  Spanning tree enabled protocol ieee
  Root ID    Priority    32868
             Address     0018.7392.c600
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32868  (priority 32768 sys-id-ext 100)
             Address     0018.7392.c600
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/2               Desg FWD 4         128.2    P2p
Gi0/3               Desg FWD 4         128.3    P2p
Gi0/23              Desg FWD 4         128.23   P2p
Gi0/24              Desg FWD 4         128.24   P2p

sh int gi0/24 status

Port      Name               Status       Vlan       Duplex  Speed Type
Gi0/24    SAN switch test    connected    trunk      a-full a-1000 10/100/1000BaseTX

STP vlan 100 on C3850 and interface status

VLAN0100
  Spanning tree enabled protocol ieee
  Root ID    Priority    32868
             Address     0056.2bd9.1e80
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32868  (priority 32768 sys-id-ext 100)
             Address     0056.2bd9.1e80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Te1/0/24            Desg FWD 4         128.24   P2p


sh int te1/0/24 status

Port         Name               Status       Vlan       Duplex  Speed Type
Te1/0/24                        connected    trunk      a-full a-1000 10/100/1000BaseTX SFP

MHM Cisco World · ‎12-26-2023

two root bridge!!!
can I see
show interface trunk in both SW

MHM

RookieNet55 · ‎12-26-2023

Here is the trunk interfaces from the core switch C3560X

sh int trunk

Port        Mode             Encapsulation  Status        Native vlan
Gi0/2       on               802.1q         trunking      100
Gi0/3       on               802.1q         trunking      100
Gi0/18      on               802.1q         trunking      218
Gi0/23      on               802.1q         trunking      100
Gi0/24      on               802.1q         trunking      100

Port        Vlans allowed on trunk
Gi0/2       2-3,52,100,218,301-304
Gi0/3       52-53,100
Gi0/18      218
Gi0/23      100
Gi0/24      1-4094

Port        Vlans allowed and active in management domain
Gi0/2       2-3,52,100,218,301-304
Gi0/3       52,100
Gi0/18      218
Gi0/23      100
Gi0/24      1-3,52,100,218,301-304,1000

Port        Vlans in spanning tree forwarding state and not pruned
Gi0/2       2-3,52,100,218,301-304

Port        Vlans in spanning tree forwarding state and not pruned
Gi0/3       52,100
Gi0/18      218
Gi0/23      100
Gi0/24      1-3,52,100,218,301-304,1000

MHM Cisco World · ‎12-26-2023

as I guess there is two native in one SW this make STP not elect the correct root and all issue you face from this misconfig
match native vlan in all your SW and check.
MHM