Need help on a trunk link.

Can you post your configs?

On the 2950 try switchport mode trunk switchport encap dot1q.

Are you using a straight through or crossover? If memory serves correctly the 3550 supports auto sensing but the 3500XL is older and probably doesn't. That could be the reason the cables seem to work on one pair of switches and not the other.

The 2950 only supports dot1q. I am currently using fa0/1 interfaces on both switches.

3500XL
Switch_B#sh run
Building configuration...

Current configuration:
!
version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch_B
!
!
!
!
!
!
!
ip subnet-zero
!
!
!
interface FastEthernet0/1
keepalive 10
switchport trunk encapsulation dot1q
switchport mode trunk
!

interface FastEthernet0/24
keepalive 10
duplex full
speed 100
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface VLAN1
no ip directed-broadcast
no ip route-cache
!
!
line con 0
logging synchronous
transport input none
stopbits 1
line vty 0 4
login
line vty 5 15
login
!
end

2950
Switch_C#sh run
Building configuration...

Current configuration : 1229 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch_C
!
!
ip subnet-zero
!
!
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
!
!
!
!
interface FastEthernet0/1
switchport mode trunk
switchport nonegotiate
!

interface FastEthernet0/24
switchport mode trunk
switchport nonegotiate
speed 100
duplex full
!
interface Vlan1
no ip address
no ip route-cache
!
ip http server
!
line con 0
logging synchronous
line vty 0 4
login
line vty 5 15
login
!
!
end

I'm using a crossover, and have tried many cables.

Is the link up/up on both sides?

If so, what happens if you blank the configs and connect them? Then do just a switchport mode trunk and switchport trunk encaps dot1q and nothing else configured?

Both sides are down/down. I've blanked both configs and tried with a blank config with no luck. The default on the 3500XL is a static access port with ISL for trunking, so I corrected those two settings and still nothing. Also, I've ensured that Vlan 1 is the native Vlan for both switches.

Have you tried another port? If both sides are down/down it doesn't sound like its a config issue.

I've tried multiple ports and multiple cables. When I connect either switch to my SwitchA, they connect without any issues. I can connect both fa0/1 ports as they are configured now to my SwitchA and they come up without any issues.

If you do a no shut what happens? What are the port states in STP?

No shut has no effect. The 2950 says No spanning tree instance exists (keep in mind this is the only connection on either switch). The 3500XL shows everything in a blocking state (which I believe is the default state). Spanning tree shouldn't be an issue with only a single link connecting the two switches.

Switch_B#sh spanning-tree sum

UplinkFast is disabled
PortFast BPDU Guard is disabled

Name Blocking Listening Learning Forwarding STP Active

VLAN1 26 0 0 0 26
VLAN50 2 0 0 0 2
VLAN100 2 0 0 0 2
VLAN150 2 0 0 0 2
VLAN200 2 0 0 0 2
VLAN250 2 0 0 0 2
VLAN300 2 0 0 0 2
VLAN400 2 0 0 0 2
VLAN500 2 0 0 0 2
VLAN600 2 0 0 0 2

10 VLANs 44 0 0 0 44

Switch_C#sh spanning-tree

No spanning tree instance exists.

More outputs:

2950
Switch_C#sh int fa0/1
FastEthernet0/1 is down, line protocol is down (notconnect)
Hardware is Fast Ethernet, address is 000c.857c.9281 (bia 000c.857c.9281)
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)
Auto-duplex, Auto-speed, media type is 100BaseTX
input flow-control is unsupported output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:08:20, output 00:08:21, 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 0 bits/sec, 0 packets/sec
437 packets input, 35648 bytes, 0 no buffer
Received 410 broadcasts (0 multicast)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 410 multicast, 0 pause input
0 input packets with dribble condition detected
14546 packets output, 1047480 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

Switch_C#sh int fa0/1 sw
Name: Fa0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: Off
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
Appliance trust: none

3550XL
Switch_B#sh int fa0/1
FastEthernet0/1 is down, line protocol is down
Hardware is Fast Ethernet, address is 0007.50ae.6301 (bia 0007.50ae.6301)
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)
Auto-duplex , Auto Speed , 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:10:13, output 00:10:12, 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
190 packets input, 37485 bytes
Received 162 broadcasts, 0 runts, 0 giants, 0 throttles
86 input errors, 29 CRC, 57 frame, 0 overrun, 0 ignored

why is this incrementing? DTP is disabled on the other switch.
0 watchdog, 162 multicast
0 input packets with dribble condition detected
1251 packets output, 92874 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 output buffer failures, 0 output buffers swapped out

Switch_B#sh int fa0/1 sw
Name: Fa0/1
Switchport: Enabled
Administrative mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Disabled
Access Mode VLAN: 0 ((Inactive))
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: 1,50,100,150,200,250,300,400,500,600
Pruning VLANs Enabled: 2-1001

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

Interesting that the 2950 says its not connected. Is the port light on? All pins present?

Sorry, I should have clarified that. Everything is connected. Different ports have been used and all with the same results. Also, different known good cables have been used and the same thing happens. No lights on either switch under any circumstance (when connecting B&C).

What happens if you unplug the cables and use terminal monitior then re plug the cables? (notconnect) is pretty strange when the cable is known to be good.

Second thought - can you undo the trunking configuration on the 2950 port, make it an access port and verify it works with a PC?

I configured it as a static access port connected to my third switch successfully. I can try using my wife's PC later today if I need to.

As far as term mon goes, this is what I get:

2950 to 3500 (good connection)
Switch_C(config-if)#
03:37:31: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, chang
ed state to down
Switch_C(config-if)#
03:37:32: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to down
Switch_C(config-if)#
03:37:40: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
03:37:41: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, chang
ed state to up

2950 to 3550XL (bad connection)
Switch_C(config-if)#shut
Switch_C(config-if)#
03:39:58: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administr
atively down
Switch_C(config-if)#no shut
Switch_C(config-if)#
03:40:04: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to down
Switch_C(config-if)#

Switch_B(config-if)#shut
Switch_B(config-if)#
03:42:21: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administr
atively down
Switch_B(config-if)#no shut
Switch_B(config-if)#
03:42:26: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
03:42:26: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to down
Switch_B(config-if)#

f0rgiv3n

I'm thinking it's a physical issue if the switch isn't seeing anything at all. No lights on the port means it doesn't have a link whatsoever! Have you tried to swing the port and cable that works in between A and B and move it to B and C, leaving the B side connected? And are you sure the crossover cable is known-good? have you hooked that up in between A and B to see if you get links between those two switches with that crossover?

f0rgiv3n wrote: »

I'm thinking it's a physical issue if the switch isn't seeing anything at all. No lights on the port means it doesn't have a link whatsoever! Have you tried to swing the port and cable that works in between A and B and move it to B and C, leaving the B side connected? And are you sure the crossover cable is known-good? have you hooked that up in between A and B to see if you get links between those two switches with that crossover?

All YES's. I can take either end of the cable and plug it into my other switch and immediately the link will come up. I can do this with multiple cables and multiple ports. I honestly wish it was just a hardware issue, but but I've tested EVERY combination of hardware to be sure that isn't the reason (unless there is some crazy reason the ports are simply incompatible).

It's got to have something to do with going from a POE device to a non POE device.

try power inline never in interface config for the POE switches switchport. Or No power inline from global config

CarlSaiyed wrote: »

try power inline never in interface config for the POE switches switchport. Or No power inline from global config

I've tried with both inline power enabled and disabled.

Switch_B(config-if)#no power inline
Switch_B(config-if)#shut
Switch_B(config-if)#
04:05:13: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administr
atively down
Switch_B(config-if)#no shut
Switch_B(config-if)#
04:05:18: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
04:05:18: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to down
Switch_B(config-if)#

brunogramalho

Have you tried to configure media-type rj45 on the 3550XL?

Have you just plugged in two blank ports and see if they come up? Need to narrow down the issue and trying to troubleshoot the config and hardware at the same time makes it difficult.

brunogramalho wrote: »

Have you tried to configure media-type rj45 on the 3550XL?

Unless I'm mistaken, that would only apply to the gig interfaces. The fa interfaces are all RJ48 ports.

networker050184 wrote: »

Have you just plugged in two blank ports and see if they come up? Need to narrow down the issue and trying to troubleshoot the config and hardware at the same time makes it difficult.

Yes, both between the two switches, and on each switch themselves.

fluk3d

del flash:/vlan.dat

fluk3d wrote: »

del flash:/vlan.dat

No, that has nothing to do with the trunk not coming up, and the vlans are good anyway. Switch A is my vtp server, with B and C as clients. Vlan replication is working fine.

So with a completely blank config on the ports they still stay down/down?