[c-nsp] Unidirectional CDP traffic

[Daniel Dib]

On to, mar 31, 2011 at 13:22:19, Gökhan Gümüş wrote:
> Subject: [c-nsp] Unidirectional CDP traffic
> 
> Hi all,
> 
> One of our customer is experiencing a strange problem.
> We are providing a link between London and Stockholm via DWDM.
> Customer is not able to ping remote site.
> Strange things from Stockholm he can see London site as CDP neighbor.
> From London he can not...
> Configs are below;
> 
> === London ===
> LIXCORML01#cle count gi3/16
> Clear "show interface" counters on this interface [confirm] 
> LIXCORML01#p 10.119.44.150
> 
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 10.119.44.150, timeout is 2 seconds:
> .....
> Success rate is 0 percent (0/5)
> 
> -----Stockholm----
> 
> SOXCORML01#sh cdp nei gi3/11
> Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
>                   S - Switch, H - Host, I - IGMP, r - Repeater, P - 
> Phone,
>                   D - Remote, C - CVTA, M - Two-port Mac Relay
> 
> Device ID        Local Intrfce     Holdtme    Capability  Platform
> Port ID
> LIXCORML01.abc <http://lixcorml01.nd.barcapint.com/>
>                  Gig 3/11          133             R S I  WS-C4900M Gig
> 3/16
> SOXCORML01#
> 
> Interface configs are below;
> 
> === London ===
> interface GigabitEthernet3/16
>  description euNetworks BAR0001_LON_STO_GE_26254_001 to SOXCORML01
> Gi3/11  switchport access vlan 628  switchport trunk native vlan 628 
> switchport trunk allowed vlan 628,728  switchport mode trunk  speed 
> nonegotiate end === === Stockholm === interface GigabitEthernet3/11 
> description euNetworks BAR0001_LON_STO_GE_26254_001 to LIXCORML01
> Gi3/16  switchport access vlan 628  switchport trunk native vlan 628 
> switchport trunk allowed vlan 628,728  switchport mode trunk  speed 
> nonegotiate  spanning-tree portfast end
> 
> === London ===
> LIXCORML01#sh int gi3/16 sw
> Name: Gi3/16
> Switchport: Enabled
> Administrative Mode: trunk
> Operational Mode: trunk
> Administrative Trunking Encapsulation: dot1q Operational Trunking
> Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 628
> (628-SOX-PROD) Trunking Native Mode VLAN: 628 (628-SOX-PROD) 
> Administrative Native VLAN tagging: enabled 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 Native VLAN tagging:
> enabled Administrative private-vlan trunk encapsulation: dot1q 
> Administrative private-vlan trunk normal VLANs: none Administrative 
> private-vlan trunk associations: none Administrative private-vlan 
> trunk
> mappings: none Operational private-vlan: none Trunking VLANs Enabled:
> 628,728 Pruning VLANs Enabled: 2-1001 Capture Mode Disabled Capture 
> VLANs Allowed: ALL
> 
> Unknown unicast blocked: disabled
> Unknown multicast blocked: disabled
> Appliance trust: none
> ===
> === Stockholm ===
> SOXCORML01#sh int gi3/11 sw
> Name: Gi3/11
> Switchport: Enabled
> Administrative Mode: trunk
> Operational Mode: trunk
> Administrative Trunking Encapsulation: dot1q Operational Trunking
> Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 628
> (628-LIX-PROD) Trunking Native Mode VLAN: 628 (628-LIX-PROD) 
> Administrative Native VLAN tagging: enabled 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 Native VLAN tagging:
> enabled Administrative private-vlan trunk encapsulation: dot1q 
> Administrative private-vlan trunk normal VLANs: none Administrative 
> private-vlan trunk associations: none Administrative private-vlan 
> trunk
> mappings: none Operational private-vlan: none Trunking VLANs Enabled:
> 628,728 Pruning VLANs Enabled: 2-1001 Capture Mode Disabled Capture 
> VLANs Allowed: ALL
> 
> Unknown unicast blocked: disabled
> Unknown multicast blocked: disabled
> Appliance trust: none
> SOXCORML01#
> ===
> 
> Anybody had such an experience before?
> 
> Thanks and regards,
> Gokhan Gumus
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If he can see London from STHLM that would imply that TX from London and RX
in STHLM is working as expected. The issue should be with LONDON RX and
STHLM TX. On the London port you have both the port configured as access and
as a trunk, that can cause weird things. Is this the same in STHLM also? You
are using speed nonegotiate which shouldn't cause issues like this but it's
better to have auto enabled unless you absolutely cannot get the link stable
with it. What about the counters for the interfaces in LONDON and STHLM, are
they increasing? And are they increasing both inbound and outbound?

/Daniel