Announcement

Collapse
No announcement yet.

Fiber Connectity issue between two Cisco 3550 Switches

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Fiber Connectity issue between two Cisco 3550 Switches

    I am facing an issue while connecting two Cisco LAN Switches Via Fiber module.
    These Two were already connected by a provider (my Location A-> provider--> My Location B) via FE ports, and working ok.

    A Fiber link between Two end was laid, link got up, but if i unplugged or shut the FE port which is via Provider to check my own Fiber connectivity, both switch don't ping each other, no data, though interface and line protocol remain up.
    Media was tested repeatedly and found no issue.

    Confs are as under

    End-A
    -----------------
    interface GigabitEthernet0/1
    switchport trunk encapsulation dot1q
    switchport mode trunk
    speed nonegotiate
    !

    End-B
    ----------------
    interface GigabitEthernet0/2
    switchport trunk encapsulation dot1q
    switchport mode trunk
    speed nonegotiate
    !

    Both Switches are Cisco 3550.

    Any possible help please....
    1- to activitate this link to full operational mode.
    2- can i set priority level too of these two link, keeping fiber link on first.

    Best regards

    Masriffa

  • #2
    Re: Fiber Connectity issue between two Cisco 3550 Switches

    When you shut the FE port down do the trunk links go down too? You can check your logs on the switch to verify that. How many vlans are on this switch. Spanning tree requires at least one active port in that vlan to keep the spanning tree instance of that vlan up.


    Also spanning tree will always prefer the fiber link as it has a lower cost and if both links are connected to the same switches spanning tree should put the fe link in a non forwarding state (loop prevention mechanism) If you have multiple vlans you can assign the spanning tree cost/priority so different vlans prefer one link over the other.


    Best thing to do is enable logging on your switches. Are you learning mac addresses across the fiber link? Also is that fiber link a direct connection or are you going through your providers equipment? (IE another provider switch)
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)

    Comment


    • #3
      Re: Fiber Connectity issue between two Cisco 3550 Switches

      thanks for the last detailed help.

      When shut the FE port access to Site-B loses the control. though Site A show up status of both controller and protocol.

      there are 3 VLAN on as under
      Vlan 100
      IP address
      for Voice
      !
      VLAN 200
      no ip address
      for data
      !
      VLAN 500
      no ip address
      for another data
      !

      in logging found a native vlan issue, correct that one on both End.
      after that observer traffic on that, but FE port too showing data in and out. according to your statement it should block FE port, but currently its not happening.
      now confs are as under

      Site-A
      -----------------
      interface GigabitEthernet0/1
      switchport trunk encapsulation dot1q
      switchport trunk native vlan 100
      switchport mode trunk
      speed nonegotiate
      !

      Site-B
      ----------------
      interface GigabitEthernet0/2
      switchport trunk encapsulation dot1q
      switchport trunk native vlan 100
      switchport mode trunk
      speed nonegotiate
      !


      both FE and GE interfaces are showing connected status.
      Fiber link is direct Switch to Switch ( no provider involved).

      hopeful for further help.

      1 question: how can i learn mac on fiber ?

      Comment


      • #4
        Re: Fiber Connectity issue between two Cisco 3550 Switches

        Assuming both uplinks are layer 2 connections the cost should be lower on the fiber connection. You can verify this by looking at the spanning tree info for your particular vlans. If for some reason the FE connection has a lower cost then you can increase on the FE connection or lower the cost on the fiber connection.

        You can view your spanning tree info for those particular ports using:


        show spanning tree interface "your interface"
        CCNA, CCNA-Security, CCNP
        CCIE Security (In Progress)

        Comment


        • #5
          Re: Fiber Connectity issue between two Cisco 3550 Switches

          FE cost is 19
          GE cost is 4

          Status of both ports are as under:

          Port Name Status Vlan Duplex Speed Type
          Fa0/2 Connected to connected trunk a-full a-100 10/100BaseTX


          Port Name Status Vlan Duplex Speed Type
          Gi0/2 Connected To connected trunk a-full a-1000 1000BaseLX


          best regards

          Comment


          • #6
            Re: Fiber Connectity issue between two Cisco 3550 Switches

            Are you learning any mac addresses on the fiber ports? Maybe try clear the mac table. Also are the gi ports in the forwarding state? Are the fe ports in the forwarding state?
            CCNA, CCNA-Security, CCNP
            CCIE Security (In Progress)

            Comment


            • #7
              Re: Fiber Connectity issue between two Cisco 3550 Switches

              yes observing MAC on GE port
              tried by clearing mac address-table, put no result, as traffic observed on both Port i.e. FE and GE ports parallel.
              Both ports (FE too) are in Forwarding states.

              hopeful for further help.


              best regards

              Comment


              • #8
                Re: Fiber Connectity issue between two Cisco 3550 Switches

                Hmm, not sure what the issue is. Is the FE circuit a layer 2 circuit? Trying to figure out if your provider is also tagging those frames in its network (Q in Q tunnel).
                CCNA, CCNA-Security, CCNP
                CCIE Security (In Progress)

                Comment


                • #9
                  Re: Fiber Connectity issue between two Cisco 3550 Switches

                  FE Circuit is a layer 2 one.

                  Further elaboration is as under
                  have 5 metropolitan, Layer 2 interconnect with Provider.
                  Provider is returning that (5 points) traffic at Centralized point, from where we are outing towards our ISP.


                  best regards

                  Comment


                  • #10
                    Re: Fiber Connectity issue between two Cisco 3550 Switches

                    The question is are they tagging the frames again in their network, which is referred to as a Q in Q tunnel.

                    http://www.cisco.com/en/US/docs/swit...nq_tunnel.html
                    CCNA, CCNA-Security, CCNP
                    CCIE Security (In Progress)

                    Comment


                    • #11
                      Re: Fiber Connectity issue between two Cisco 3550 Switches

                      According to the provider statement, tunneling is being done between two points.
                      Fiber connectivity is between there SDH (no idea about their SDH vendor) and my end Cisco Lan Switch (at my described end, its connected in Cisco at Ethernet Port, Media convertor is being used for fiber to ethernet conversion).

                      Comment

                      Working...
                      X