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New Member

VSS Switchport Issue

Hello Guys,

I am having an issue withVSS ports that I was hopingyou could assist with. I have a pair of 4500x switch, and VSS is completely configured and working properly, however when I uplink both switches using the same port on both to another switch, I cannot pass traffic between them. I have a trunk port setup on both ends, and vlans on both sides, however traffic doesn't cross the trunks. I have tested these same ports as layer 3 routed ports and they work fine. I uplink directly into my laptop with them using a copper GBIC, but when i connect to another cisco switch, traffic does not pass. Could there be a setting im missing to be configrued on the 4500x switches?

  • LAN Switching and Routing
1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: VSS Switchport Issue

John

A thought occured to me after i logged off last night.

The switch is using 100Mbps connections. Is the router doing the same ?

Are the ports on the 4500 you are connecting to capable of running 10/100/1000Mbps connections ?

Jon

22 REPLIES
Hall of Fame Super Blue

Re: VSS Switchport Issue

John

Are you using an etherchannel  to connect to the other switch ? Can you post the config for the connection from all switches + a "sh int trunk" (assuming it is a trunk) from both ends.

Jon

New Member

Re: VSS Switchport Issue

Hey Jon,

Thanks for the prompt response, I've attached the requested config output below. If you need anything else, just let me know. I am tryin to communciate over VLAN 19.

Cisco Layer 2 Switch

interface FastEthernet0/1

switchport mode trunk

!

interface FastEthernet0/2

switchport mode trunk

!

Switch# show int trunk

Port        Mode             Encapsulation  Status        Native vlan

Fa0/1       on               802.1q         trunking      1

Fa0/2       on               802.1q         trunking      1

Port        Vlans allowed on trunk

Fa0/1       1-4094

Fa0/2       1-4094

Port        Vlans allowed and active in management domain

Fa0/1       1,19-20,200

Fa0/2       1,19-20,200

Port        Vlans in spanning tree forwarding state and not pruned

Fa0/1       1,19-20,200

Fa0/2       1,19-20,200

Cisco 4500x Switch Primary

interface TenGigabitEthernet1/1/3

description UPLINK_TO_SWITCH

switchport mode trunk

interface TenGigabitEthernet2/1/3

description UPLINK_TO_SWITCH

switchport mode trunk

4500x#show int trunk

Port        Mode             Encapsulation  Status        Native vlan

Te1/1/3     on               802.1q         trunking      1

Te2/1/3     on               802.1q         trunking      1

Po10        on               802.1q         trunking      1

Po20        on               802.1q         trunking      1

Port        Vlans allowed on trunk

Te1/1/3     1-4094

Te2/1/3     1-4094

Po10        1-4094

Po20        1-4094

Port        Vlans allowed and active in management domain

Te1/1/3     1,19-20,200

Te2/1/3     1,19-20,200

Po10        1,19-20,200

Po20        1,19-20,200

Port        Vlans in spanning tree forwarding state and not pruned

Te1/1/3     1,19-20,200

Te2/1/3     1,19-20,200

Po10        none

Po20        none

Hall of Fame Super Blue

VSS Switchport Issue

John

Can you post "sh spanning-tree vlan 19" from the switches ?

So these are individual trunks by the look of it. Is there a reason you have not used a port channel from the L2 switch to the 4500s which is a more common setup with VSS ie.

the L2 switch has both ports in an etherchannel and then each link is terminted on a different 4500.

Finally, how exactly are you testing this ie. from a client in vlan 19 on the L2 switch to client attached to the 4500s or between the switches. Perhaps you can clarify ?

Jon

New Member

VSS Switchport Issue

Hey Jon,

Below is the output fronm show spanning tree on both switch. Correct individual trunks. Looking at the output below, it looks like both switches are reporting as the bridge. Could that be the issue I am having?

As far as testing goes, I have a client laptop in the 2960 switch, in vlan 19. It hs an IP on that vlan, and I have an SVI for vlan 19 setup on both the 2960 and the 4500x. The laptop cannot traverse the trunks to get to the 4500x SVI for vlan 19.

4500x#show spanning-tree vlan 19

VLAN0019

  Spanning tree enabled protocol ieee

  Root ID    Priority    32787

             Address     7c69.f667.57b0

             This bridge is the root

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32787  (priority 32768 sys-id-ext 19)

             Address     7c69.f667.57b0

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type

------------------- ---- --- --------- -------- --------------------------------

Te1/1/3             Desg FWD 4         128.3    P2p

Te2/1/3             Desg FWD 4         128.1283 P2p

Switch#show spanning-tree vlan 19

VLAN0019

  Spanning tree enabled protocol ieee

  Root ID    Priority    32787

             Address     001b.0dea.e200

             This bridge is the root

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32787  (priority 32768 sys-id-ext 19)

             Address     001b.0dea.e200

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1            Desg FWD 19        128.1    P2p

Fa0/2            Desg FWD 19        128.2    P2p

Hall of Fame Super Blue

VSS Switchport Issue

John

STP is certainly not right as they both see themselves as root. You do actually have a loop. Imagine a switch connected to another switch with two separate links, this is what you have and STP should be blocking one of those ports. I'm not sure why it hasn't unless it somethig specific to VSS.

Is the 2960 a new switch to be added ?

If so can you change the config to use an etherchannel on both ends of the link rather than separate trunk links because i think this has the potential to cause big problems for you.

Jon

New Member

VSS Switchport Issue

Hi Jon,

I've now tried to connect a router directly into the 4500x, and the 4500x's cannot see this either. It couldnt see the switch with cdp neighbor, and now cannot see the router. This is also probably why spanning tree had two separate instances. I would have to assume the issues is with these 4500x switches, but the issue seems to be only when connected to cisco devices.

I am using copper GBICs, so maybe this is the issue as well, but the interfaces look clean. Could VSS be causing these issues, and are communication issues with 4500x switches configured with VSS a known issue?

New Member

VSS Switchport Issue

I have confirmed when I assign a static IP to the 4500x switch port with the copper GBIC and directly connect my laptop into it I can ping it, however when I directly connect a Cisco 1800 Router the ping fails.

New Member

VSS Switchport Issue

actually i apoligize Jon, The issue seems to be with the switchports on the 4500x. most lilely pointing to the copper gbics. I have thousands of CRC errors on both ports.

New Member

VSS Switchport Issue

sorry for all the messages lol. Do u have any idea why these GBICS wouldn't work and are cuasing thousands of CRC errors. These are brand new GLC-T 1000Base T Copper GBICs from Cisco, and both are showing CRC errors, only when connected to the cisco router and cisco switch. When I directly connect the ports to my laptop, the CRC errors stop.

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