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New Member

Verifying Trunk vlan tagging

Hello,

I have a 2960 switch connected to another. The I need to verify that vlan0010 on one switch is forwarding tagged traffic between the other switch it is hooked up to through the Gi0/1 port. How do I verify this? I have a server that's multihomed (Broadcom) on the other side an it is supposed to be on this vlan with one of it's network interfaces. We had a pwer outage and now it cannot communicate on this vlan. However, everything else on the vlan can reach all the other nodes accept this server in the front of my building. All the devices in the same room are linked to the same switch which has one port (fa0/17) on vlan0010 and can ping eachother just fine. The server is hooked to port 24 on my server room switch and Gigabit port one goes to a fiber converter all the way to the back. It then gets converted from fiber to cat5e again and links into the switch (2960) in the backroom. Any help appreciated.

Thanks,

Jeff

Everyone's tags (4)
5 REPLIES

Re: Verifying Trunk vlan tagging

try this:

switchport nonegotiate

on the trunk interface and make sure that the vlan is allowed on that trunk.

a question, if there is only a server off interface fa0/24 that needs to speak only with the subnet in vlan 10, why did you set a trunk rather then a static access port?

interface fa0/24

sw mo acce

sw access vlan 10

end

wr mem

!

Alessio

New Member

Verifying Trunk vlan tagging

I am ressurecting this thread again to follow up on this question. Why would I not use trunking to enable the other switch to know about my vlan on the other switch? This was the way it was configured when I started working at this location. Would static switch access be a better choice to do in  this case?

Thanks,

Jeff

Re: Verifying Trunk vlan tagging

Hey, u can check the trunk between the switches and the server with "show interface trunk" command. If that doesn't help send me more details about the trunk config please of the inter connecting ports and the server port.

Sent from Cisco Technical Support iPhone App

New Member

Verifying Trunk vlan tagging

Ok. Here is what I have on this so far. Vlan port assignment somehow got wiped out. I went in and put the right port back on the switch in my front room. Now the server interface can communicate with everything on vlan0010 with addresses 192.168.2.x except for .10. I keep getting request timed out for this one. I put a static IP on my wired laptop adapter that is in the same address range asnd I can ping everything consistently just fine on that vlan. My question now is why can't my server ping just this one IP address when my laptop has not an issue at all getting to it? By the way something else interesting. Earlier this morning I could ping everything on the network except .20. I bring the server back up from a restart (Dell R710 with Broadcom 5709C NetXtreme 2) and then I can't reach .10. subsequent resatrts and I still cannot reach .10 but I can reach everything else.

I mirrored a port to capture everything from the switch in the back room to port 23. I hooked into port 23 with wireshark and saw the pings going back and forth but I also saw loads of multicast traffic going to 239.192.2.x, 239.192.3.x, and 239.192.4.x Turns out these multicast transmittions are from my Allen Bradely PLC interface (3 of them). With IGMP on by default I'm thinking this can't be causing too much of an issuie but then again this multicast traffic accounts for over %50 of my pcap.

Alessio--shouldn;'t I have trunking enabled when linking 2 Cat 2960s together that need to be aware of the same vlan? What would be the configuration for two switches for static access?

Verifying Trunk vlan tagging

Hi Jeff,

When you set a trunk you are only tagging frame. Indeed nothing changes except this tag more. From this the communication can happen as long as you are in the same broadcast domain:

Switch A

Conf t

Int fa0/1

Des non-trunk pipe to switch b

Sw

No sh

Sw mo acc

Sw acc vlan 10

Speed 100

Duplex full

Speed nonegotiate

End

Wr

!

Switch B

Conf t

Int fa0/10

Des non-trunk pipe to switch a

Sw

No sh

Sw mo acc

Sw acc vlan 10

Speed 100

Duplex full

Speed nonegotiate

End

Wr

!

Clearly, only one vlan will work in your domain that in most of the cases is a quite relevant restriction

Hth

Alessio

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