Can't get 2950 to link via IP

Unanswered Question
Nov 13th, 2007

I've got a catalyst 2950 which I've just done the initial configuration on. I've set the IP address of the switch, and with a PC plugged directly in, I can reach it via ping, telnet, and http. However, when I plug the same port into another switch (netgear, non-managed switch), I can not reach it. I've tried both a straight-through and a crossover ethernet cable.

When I attach the 2950 to the other switch, I get the following messages on the console:

00:03:47: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/1 VLAN1.

00:03:47: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/1 on VLAN0001. Inconsistent port type.

but can't figure out how to configure the 2950 to correct this.

thanks for any info,

-Ben

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allan.thomas Tue, 11/13/2007 - 13:02

Essentially the log message are indicating that the port types are inconsistent at both ends.

It appears that the port on the non-managed switch which you are connecting to is configured as Trunk interface, whereas the port on the 2950 is configured as an access port. Spanning-Tree will blocked this port in this condition, once the port types are correct, the port will forward again.

If you are trunking on this port then ensure that you configure your encapsulation as 802.1Q and not ISL.

Regards

Allan.

Seem like you have a mis-match on the port configuration. The switch says it received a BPDU on a non trunk port, BPDU are used in VPT vlan configuration and on trunk links. Do a show interface on the port and see if it is setup as a trunk link, use the info below to config your port.

CLI: Disabling a Trunk Port

You can disable trunking on a port by returning it to its default static-access mode.

Beginning in privileged EXEC mode, follow these steps to disable trunking on a port:

Command Purpose

Step 1

configure terminal

Enter global configuration mode.

Step 2

interface interface_id

Enter the interface configuration mode and the port to be added to the VLAN.

Step 3

no switchport mode

Return the port to its default static-access mode.

Step 4

end

Return to privileged EXEC.

Step 5

show interface interface-id switchport

Verify your entries.

In the display, check the Negotiation of Trunking field.

The "Finding More Information About IOS Commands" section contains the path to the complete IOS documentation.

CLI: Defining the Allowed VLANs on a Trunk

By default, a trunk port sends to and receives traffic from all VLANs in the VLAN database. All VLANs, 1 to 1005, are allowed on each trunk. However, you can remove VLANs from the allowed list, preventing traffic from those VLANs from passing over the trunk. To restrict the traffic a trunk carries, use the remove vlan-list parameter to remove specific VLANs from the allowed list.

A trunk port can become a member of a VLAN if the VLAN is enabled, if VTP knows of the VLAN, and if the VLAN is in the allowed list for the port. When VTP detects a newly enabled VLAN and the VLAN is in the allowed list for a trunk port, the trunk port automatically becomes a member of the enabled VLAN. When VTP detects a new VLAN and the VLAN is not in the allowed list for a trunk port, the trunk port does not become a member of the new VLAN.

Beginning in privileged EXEC mode, follow these steps to modify the allowed list of a 802.1Q trunk:

Command Purpose

Step 1

configure terminal

Enter global configuration mode.

Step 2

interface interface_id

Enter interface configuration mode and the port to be added to the VLAN.

Step 3

switchport mode trunk

Configure VLAN membership mode for trunks.

Step 4

switchport trunk allowed vlan remove vlan-list

Define the VLANs that are not allowed to transmit and receive on the port.

The vlan-list parameter is a range of VLAN IDs Separate nonconsecutive VLAN IDs with a comma and no spaces; use a hyphen to designate a range of IDs. Valid IDs are from 2 to 1001.

Step 5

end

Return to privileged EXEC.

Step 6

show interface interface-id switchport allowed-vlan

Verify your entries.

Step 7

copy running-config startup-config

Save the configuration.

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