Cisco 7000 Series Routers

Updated March 26, 1998

March 16, 1998

Products Affected

Cisco IOS Versions Affected

Table 1: The Cisco IOS Software revisions below are affected by CSCdj52309.

The system conditions that could cause one of the described failure conditions to occur are expected to be rare; however, because of the severity of the problems, the Cisco IOS software images listed in Table 1 are deferred (not posted on CCO) as of March 16, 1998 and linestopped (no orders will be shipped with these images), as of March 13, 1998.

Table 1-Affected/Deferred Images

Problem Description

A catastrophic problem has been identified that affects all 7500 and Catalyst 5000 RSM users. The problem occurs when using packet tunneling* in combination with certain timing conditions, packet sizes, and buffer-usages. Affected images are being deferred and special images are being built.

Bug Details

For more information, refer to Cisco bug ID CSCdj52309 (registered customers only) - Packet errors when using pak_copy().

When the packet tunneling* logic on systems equipped with Route Switch Processors (RSPs) or Route Switch Modules (RSMs) causes datagrams to be copied from SRAM to DRAM, an arithmetic error results in more bytes being copied than is remembered for cleanup processing. Re-uses of the tunneling* logic, in certain rare combinations of timing, packet-sizes, and buffer-usages, may result in those unaccounted bytes causing several anomalous system behaviors including:

• packet errors

• possibly other anomalous errors

This software defect is exposed to all RSP and RSM images in the releases stated in Table 2.

It is strongly recommended that 7500 and Catalyst 5000 RSM customers install the solution and upgrade all Cisco 7500 and Catalyst 5000 RSM products using the Cisco IOS versions described in Table 3 below.

^* Tunneling is being used as an abbreviation in this context to refer to a specific fast-switch to process-level code path traversed by Translational (TLB), Source Route (SRB), and Remote Source Route Bridging (RSRB).

Workarounds

There are two possible workarounds. Cisco bug ID CSCdj33812 provides a configuration command to avoid the software defect. This workaround is available in the Cisco IOS version listed in Table 2 below. If the versions in use are below Table 2 versions, use the second workaround.

Warning:?The two workarounds may drop performance down approximately 40 percent from the standard cached performance.

CSCdj33812 Workaround for CSCdj52309

Table 2-Cisco bug ID CSCdj33812 is supported as of:

Cisco bug ID CSCdj33812 incorporated a configurable command that will be stored in NVRAM.

Configure memory cache-policy io uncached to workaround CSCdj52309. To determine what memory cache policies are currently configured on your router, use the show rsp command.

Router#config
  Configuring from terminal, memory, or network [terminal]?
  Enter configuration commands, one per line.  End with CNTL/Z.
  Router(config)#memory cache-policy io uncached  
  Router(config)#end

  Router#show rsp
  Throttle count 0, DCL timer count 0 active 0, configured 1
  netint usec 4000, netint mask usec 200
  DCL spurious 0

 Caching Strategies:
  Processor private memory: write-back
  Kernel memory view: write-back
  IO (packet) memory: uncached
  Buffer header memory: uncached
 
 Router#

To restore the MEMD caching policy to the original write-through policy, issue the memory cache-policy io write-through command.

Note:?The command no memory cache-policy io uncached will not work.

Router#config
 Configuring from terminal, memory, or network [terminal]?
 Enter configuration commands,one per line.  End with CNTL/Z.
 Router(config)#memory cache-policy io write-through
 Router(config)#end

 Router#show rsp
   Throttle count 0, DCL timer count 0
 active 0, configured 1
 netint usec 4000, netint mask usec 200
 DCL spurious 0
 
 Caching Strategies:
   Processor private memory: write-back
   Kernel memory view: write-back
   IO (packet) memory: write-through
   Buffer header memory: uncached

If operating with images that do not have the Cisco bug ID CSCdj33812 support, use the following command:

Router#
Router#test rsp cache memd-fastswitch uncache
Router#

Note:?The above command will need to be entered after every reload.

Solution

To eliminate the problems mentioned in the preceding section, Cisco strongly recommends that you download and install one of the Cisco IOS software release updates listed in Table 3 below.

Table 3 : Cisco IOS Software Release Updates

^*111.2(12a) is based off of 11.2(12) maintenance release plus CSCdj52309 fix.

^*2 11.2(12a)P is based off of 11.2(12)P maintenance release plus CSCdj52309 fix.

^*3 11.2(12a)BC is based off of 11.2(12)BC maintenance release plus CSCdj52309 fix.

^*4 11.3(2a) is based off of 11.3(2) maintenance release plus CSCdj52309 fix.

^*5 11.3(2a)T is based off of 11.3(2)T maintenance release plus CSCdj52309 fix.

Next interim build (.3) will contain fix plus .1 and .2 interim build fixes.

Other Considerations

Cisco IOS 10.3, 11.0, and 11.1 Major and ED releases are not exposed to CSCdj52309. Though these releases share the same arithmetic problem, the tunneling* software is different, and there is no known or predicted combination of timing, packet-sizes, and buffer-usages which results in the same or different anomalous behaviors associated with the releases describe in the section Solution.

Cisco bug ID CSCdj52309 is used to repair the arithmetic problem in 10.3, 11.0, and 11.1 releases; however, no special images are being created because the anomalous behaviors are not present in those releases.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

• Open a service request on Cisco.com
• By email
• By telephone

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