I agree with Fredrik. If both ports are set to switchport mode access and the access VLAN on each port is VLAN 1, then native VLAN mismatch really should have no impact on connectivity.
You may have an unnecessary "switchport trunk native vlan x" command in the configuration of one or both ports, left over from when it may have been configured as a switchport mode trunk. Double-check your config for this. It is not uncommon to have several switchport trunk-related commands remain in the config when the port mode is changed from trunk to access.
Even though the ports are set up for access mode, CDP will communicate any relevant information about the port configurations to other Cisco devices which may be attached to them. If this message is really annoying, you can turn off CDP on just those ports, as Fredrik suggests; but then you would lose the benefit of having CDP exchange other important information between the two switches.
Try sh cdp nei details to see what native VLAN number is advertised from the opposite side.
If you were not able to fix the problem by removing config trunk commands, you don't have to disable CDP on the port. You can just degrade it to CDP ver 1 (not sending native VLAN info) by no cdp advertise-v2 (an disadvantage is that this is a global command).
Are the 3550 ports configured as routed ports (i.e. no switchport)? I have seen the exact same thing with Catalyst 6500's running Native IOS connected to 3500XL switches. I think CDP is trying to be too clever in reading the VLAN ID from the CDP messages it receives; I think there is no VLAN ID in the CDP messages from the routed ports. I am sure everything will work fine but the messages are damn annoying. I suggest turn CDP off the 2950s?
[toc:faq]The ProblemOn traditional switches whenever we have a trunk
interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...