Troubleshooting: 3550-2 fa0/1 amber.

fa0/1 of 3550-2 is amber; bad!
Device ID Local Intrfce Holdtme Capability Platform Port ID
2950-1 Fas 0/2 124 S I WS-C2950- Fas 0/2

only one is connected, no cdp packets received from fa0/1 of 2950.

3550-2#sh int status

Port Name Status Vlan Duplex Speed Type
Fa0/1 connected 1 a-full a-100 10/100BaseTX
Fa0/2 connected 1 a-full a-100 10/100BaseTX
<output truncated>

3550-2#sh run int fa0/1
Building configuration…

Current configuration : 68 bytes
!
interface FastEthernet0/1
switchport mode dynamic desirable
end

3550-2(config)#int fa0/1
3550-2(config-if)#switchport mode trunk
Command rejected: An interface whose trunk encapsulation is “Auto” can not be configured to “trunk” mode.

3550-2#sh dtp int fa0/1
DTP information for FastEthernet0/1:
TOS/TAS/TNS: ACCESS/DESIRABLE/ACCESS
TOT/TAT/TNT: NATIVE/NEGOTIATE/ISL
Neighbor address 1: 000000000000
Neighbor address 2: 000000000000
Hello timer expiration (sec/state): 19/RUNNING
Access timer expiration (sec/state): never/STOPPED
Negotiation timer expiration (sec/state): never/STOPPED
Multidrop timer expiration (sec/state): never/STOPPED
FSM state: S2:ACCESS
# times multi & trunk 0
Enabled: yes
In STP: no

Statistics
———-
0 packets received (0 good)
0 packets dropped
0 nonegotiate, 0 bad version, 0 domain mismatches,
0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other
98 packets output (98 good)
49 native, 49 software encap isl, 0 isl hardware native
0 output errors
0 trunk timeouts
1 link ups, last link up on Mon Mar 01 1993, 00:00:43
0 link downs

Is my 3550-2 trying to negotiate an ISL from 2950? 2950 does not support ISL…

3550-2(config-if)#switchport trunk encapsulation dot1q
3550-2(config-if)#
*Mar 1 00:28:18.295: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
3550-2(config-if)#
*Mar 1 00:28:21.295: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
3550-2(config-if)#
*Mar 1 00:28:21.915: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/1 VLAN1.
*Mar 1 00:28:21.915: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/1 on VLAN0001. Inconsistent port type.

Anyway I turn off negotiate, and specify dot1q to be the vlan encapsulation for trunking. Now fa0/1 is in inconsistent state. But I can hardcode my fa0/1 as a trunk now. So previously my fa0/1 was in negotiating mode.

3550-2(config-if)#switchport mode trunk
3550-2(config-if)#
*Mar 1 00:31:08.623: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
3550-2(config-if)#
*Mar 1 00:31:11.635: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
3550-2(config-if)#
*Mar 1 00:31:11.915: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 100 on FastEthernet0/1 VLAN1.
*Mar 1 00:31:11.915: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking FastEthernet0/1 on VLAN0001. Inconsistent local vlan.

Ha… this means native vlan of 3550-2 fa0/1 and 2950-2 fa0/1 are different. But anyway now the fa0/1 of 3550-2 is green.

3550-2(config-if)#
3550-2(config-if)#
*Mar 1 00:31:26.915: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking FastEthernet0/1 on VLAN0001. Port consistency restored.

After awhile port consistency restored.. it is quite slow…hmm…

3550-2#sh cdp nei
Capability Codes: R – Router, T – Trans Bridge, B – Source Route Bridge
S – Switch, H – Host, I – IGMP, r – Repeater, P – Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID
2950-2 Fas 0/1 154 S I WS-C2950- Fas 0/1
2950-1 Fas 0/2 155 S I WS-C2950- Fas 0/2

Ok, all is working now…