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Cisco Bug: CSCuk55193 - Router crashes in tdp_rx_notify after disabling tag switching

Last Modified

Jan 31, 2017

Products (1)

  • Cisco IOS

Known Affected Releases

12.2S

Description (partial)

Symptoms: On a router that runs Cisco IOS Release 12.2S and that is configured 
for Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP), a 
configuration change that causes one or more LDP sessions to be terminated may 
cause the router to reload in a manner similar to the following:

%ALIGN-1-FATAL: Illegal access to a low address
addr=0x64, pc=0x41285C40, ra=0x41285C30, sp=0x44B1C378
  
%ALIGN-1-FATAL: Illegal access to a low address
addr=0x64, pc=0x41285C40, ra=0x41285C30, sp=0x44B1C378
  
TLB (store) exception, CPU signal 10, PC = 0x41285C40

The symptom may occur with either LDP or Tag Distribution Protocol (TDP). 

Conditions: This symptom is extremely unlikely to occur and requires 
a very unlikely timing of events between LDP and TCP. The symptom may occur in 
the following releases and their rebuilds: Release 12.2(18)S, 12.2(20)S,
12.2(22)S, and 12.2(25)S.

There are many configuration commands that may trigger the symptom, including 
entering the <CmdBold>no ip vrf<noCmdBold> command to remove a VRF that has
LDP-enabled interfaces, entering the <CmdBold>no mpls ldp router-id<noCmdBold> 
command to trigger a change to the LDP router ID, or entering the <CmdBold>no 
mpls ip<noCmdBold> interface configuration command to disable LDP on an 
interface.
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Bug Details Include

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