2950 Can't not pingable, CDP half operational

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Nov 12th, 2008
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I have got a 2950 EI running 12.1.19 EA10. It is connected via fiber to a 3550-12G running 12.2.44. The port on the 3550 is set to access mode and the 2950 has no config on it's port. The 2950 sees the 3550 via CDP but the 3550 does not see the 2950 via CDP. CDP is enabled on both and on all ports. The 2950 is also no pingable and can not ping anything itself. VLAN 1 does have an ip is no shutdown. I have wr erased and reloaded and still get the same thing. Do i need to upgrade the IOS? Even if I am directly connected to the switch I can't ping so if i need to upgrade i will probably have to Xmodem..

The strange thing is pcs connected to it work fine so I know traffic is flowing.

Thanks in advance for the assistance!

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Giuseppe Larosa Wed, 11/12/2008 - 10:01
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Hello Matthew,

verify with sh int gx/y switchport if they have negotiated a trunk.

both symptoms point to a native vlan mismatch.

Hope to help


MUHAMMAD SHAHEEN Wed, 11/12/2008 - 12:50
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on the switch port at 3550 connecting to 2950 switch, issue the following 2 commands, this should fix the problem.

swithport mode trunk

switchport trunk encap dot1q

then configure your 2950 with ip address.

Hope this helps...


glen.grant Wed, 11/12/2008 - 12:54
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Sounds like it trunked the port and you have a native vlan mismatch which can screw up cdp . Put switchport mode access on your 2950 so it can't trunk, by default it will try to trunk as the port is defaulted as "desirable". If still having a problem post your link configs for both sides. The 2950 has to have an address and a default gateway set . You do not need to upgrade any code , the config is wrong somewhere.


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