From: Ken Diliberto (ken@kdmd.net)
Date: Fri Oct 10 2003 - 00:39:45 GMT-3
Take this example:
PC1-SW1===SW2-PC2
PC1 - Personal Computer #1
PC2 - Personal Computer #2
SW1 - Switch #1
SW2 - Switch #2
The === is a redundant link of Fast Ethernet or GigEthernet. For this
example, we'll say GigE. SW1 G0/1 connects to SW2 G0/1, SW1 G0/2
connects to SW2 G0/2. Spanning Tree has G0/2 on SW2 in blocking state.
If something goes bonkers (technical for "What just happened???" or "Is
the network down again???") then SW2 might see the MAC address for PC1
move from G0/1 to G0/2. This could happen if Spanning Tree reconverges
because PC1 turns on bridging or one of the switches decides it's time
to recalculate it's topology. When everything settles down, PC1 might
move back to G0/1 from G0/2.
If conditions are really bad, both G0/1 and G0/2 could go into
forwarding at the same time. The SW2 sees PC1 on both G0/1 and G0/2,
but processes the MAC address on one port at a time. The resulting
message might be something like this:
%RTD-1-ADDR_FLAP G0/1 relearning 10000 addrs per min.
Add more PC/end node devices and you'll get higher numbers for [dec].
Another cause to consider:
An office has 2 network jacks which happen to plug into different
switches. PORTFAST is configured on each port. The person in the
office thinks they can double their bandwidth by plugging both jacks
into the same hub with their three machines. You've now set the
conditions for this problem. Sometimes it's easy to find while others
it's very difficult.
YMMV, Some assembly required, batteries not included, etc.
Hope this helps.
Ken
Tom Young wrote:
> I found the error message of my switch on cisco website.
> But My english is very poor, could understand it 100%, who
> can explain it more detaily ?
>
> Thanks alot
>
> 1. %RTD-1-ADDR_FLAP [chars] relearning [dec] addrs per min
>
> Normally, MAC addresses are learned once on a
> port.Occasionally, when a switched network reconfigures,
> due to either manualor STP reconfiguration, addresses
> learned on one port are relearned on adifferent port.
> Howeve r, if there is a port anywhere in the switched
> domainthat is looped back to itself, addresses will jump
> back and forth between the real port and the port that is
> in the path to the looped back port. Inthis message,
> [chars] is the interface, and [dec] is th e number of
> addressesbeing learnt.
>
>
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This archive was generated by hypermail 2.1.4 : Mon Nov 24 2003 - 07:52:59 GMT-3