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Cisco IOS Software Releases 11.2

Field Alert: EIGRP and ARP Issues in Cisco IOS Software Releases 11.1 and 11.2


Updated January 19, 1998


Description

Read this entire document carefully. It has been updated since its initial release to include important new defect and resolution information.

This notice describes unexpected behavior of the EIGRP routing protocol and the Address Resolution Protocol (ARP), and other symptoms related to IP protocols. Listed below are the products affected, a description of the symptoms, and details about specific software defects that have been submitted against these behaviors.

Cisco Systems, Inc. strives to maintain the highest software quality standards in the internetworking industry. We also seek to provide you, our customers and partners, with the most thorough and advanced software quality information as part of the services available under your Cisco service agreement.

Products Affected

The Cisco IOS Software revisions below are affected by CSCdj60533 and CSCdj58676, except where noted.

Software Release

Images Affected

Resolution

11.2

All images 11.2(9.1) - 11.2(10), 11.2(10a) **

11.2(11)

11.2P

All images 11.2(9.1)P - 11.2(10)P, 11.2(10a)P **+

11.2(10a)P1, 11.2(11)P

11.2BC

All images 11.2(9.1)BC - 11.2(10)BC, 11.2(10a)BC **

11.2(11)BC

11.2XA

All images 11.2(9)XA & 11.2(9)XA1

N/A ++

11.1 *

All images 11.1(15.1) - 11.1(15.5)

11.1(16)

11.1AA *

All images 11.1(15.1)AA - 11.1(15.5)AA

11.1(16)AA

11.1CA *

All images 11.1(15)CA - 11.1(15.5)CA

11.1(16)CA

11.1IA *

All images 11.1(15)IA - 11.1(15.5)IA

11.1(16)IA

* 11.1-based releases affected by CSCdj58676 only

** All (10a) releases also affected by CSCdj65737

+ 11.2(10a)P c5300 images also affected by CSCdj58853

++ See explaination for XA releases in "Workarounds and Solutions" section

Problem Description

Description of IP Protocols Defect CSCdj60533

The ARP lookup routine may suspend, causing unexpected behaviors for IP protocols. For example, if the OSPF routing process is traversing a list of neighbors to send LSA packets and the ARP routine is called, the ARP routine suspension could cause a system reset.

This defect was introduced by code changes associated with CSCdj39289. The change made by CSCdj60533 is to back out the code committed by CSCdj39289, therefore the behavior reported in CSCdj39289 may still occur, for instance, packets generated by the router itself (such as syslog) may be dropped while ARP lookup takes place.

Description of EIGRP Defect CSCdj58676

This defect was introduced by code changes associated with CSCdj28874. This defect affects redistribution of routes into the EIGRP routing process. The following types of routes may not be correctly redistributed:

  • A directly connected route

  • A static route with the next hop set to an interface

  • A static route with the next hop set to a dynamically learned route

The defect becomes apparent only after a dynamic event, therefore when redistribution is initially configured, EIGRP will reflect correct information in the topology table, however after any sort of dynamic event (such as an interface-changing state) the topology table is no longer valid and routing updates sent will be inaccurate.

Description of EIGRP Redistribution Defect CSCdj65737

This defect was introduced by code changes associated with CSCdj58676. The issue is that routes are not being redistributed into EIGRP from other routing protocols, if both protocols are routing for the same major network. The code changes for CSCdj58676 were only applied to 11.2(10a), 11.2(10a)BC and 11.2(10a)P releases, therefore, those releases are the only ones impacted by CSCdj65737.

Description of EIGRP Redistribution Defect CSCdj28874

When a network is included in the EIGRP routing process because it is specified with the network x.x.x.x command and that same network is redistributed into EIGRP via the redistribute connected command, there will be two entries for the network in the EIGRP topology table.

If the interface connecting that network goes down, only one of the two entries will be removed from the topology table. The entry learned via redistribution will remain in the topology table and be advertised, even though it is no longer valid.

Description of EIGRP Defect CSCdj58853

This defect only affects the AS5300 platform (c5300 images) for release 11.2(10a)P. The symptom is that EIGRP summary routes are not being advertised. The specific failure found by Cisco internal testing is that routes assigned to the address pool for dial-up clients are not being advertised as summary routes. This symptom has not been reported in a customer environment to date.

If you are a registered CCO user and you have logged in, you can view bug details.

Workarounds and Solutions

A workaround for both CSCdj60533 and CSCdj39289 is to configure static ARP cache entries for devices on LAN segments with the router until a new software version containing the fix is released. This approach may not be viable for segments with many hosts, however, for backbone or DMZ/firewall segments with few hosts and routers, this is recommended. It is also possible to decrease the possibility of problem occurrence by increasing the timeout value for ARP cache entries. The default timeout interval is four (4) hours.

Both CSCdj58676 and CSCdj60533 will be resolved as of Cisco IOS Software Releases 11.2(10a), 11.2(10a)P and 11.2(10a)BC. Release 11.2(11)P will be the upgrade path for customers currently using 11.2(9)XA or 11.2(9)XA1.

CSCdj58676 will be resolved as of Cisco IOS Software Releases 11.1(16), 11.1(16)AA, 11.1(16)CA, and 11.1(16)IA.

The following Cisco IOS software releases are deferred, have been removed from availability on the CCO Software Center, and will not be available through manufacturing:

  • 11.2(10) - All images

  • 11.2(10)P - All images

  • 11.2(10)BC - All images

11.1-based releases are affected only by CSCdj58676 and are not being deferred. Customers using or wishing to use an affected 11.1-based release should review their configurations and determine if the defect applies to them.

11.2(9)XA and 11.2(9)XA1 are affected by both CSCdj58676 and CSCdj60533 and are not being deferred. These releases are intended for a very limited set of Cisco products (AS5300 and Cisco 3600 with digital modem Network Modules). Typical network topologies for AS5300 installations are not likely to experience the symptoms caused by CSCdi60533, and the workaround of using static ARP cache entries is viable in most cases.

Typical network topologies for C3600 installations are somewhat likely to experience the symptoms caused by CSCdj60533 and that should be considered when deploying release 11.2(9)XA for digital modem support.

Important Update Note

The code changes committed by CSCdj58676 resolved some issues, but created the symptoms reported in CSCdj65737. The code changes for CSCdj58676 were only committed to releases 11.2(10a), 11.2(10a)BC and 11.2(10a)P, therefore they are the only ones affected by CSCdj65737.

The fix to CSCdj65737 will be to back out the code changes committed by CSCdj58676 and CSCdj28874. That change will have the effect of reintroducing the behavior reported by CSCdj28874. The code back-outs of CSCdj65737 and reintroduction of CSCdj28874 will appear in the following releases:

  • 11.2: 11.2(11), 11.2(11)BC, 11.2(11)P

  • 11.1: 11.1(16), 11.1(16)AA, 11.1(16)CA, 11.1(16)IA

All defect resolution information pertaining to CSCdj58676 is superseded by the details relating to CSCdj65737.

You can avoid the symptoms of CSCdj28874 by specifying only individual networks that are not directly connected to be redistributed into EIGRP instead of using the redistribute connected command.

CSCdj58853 affects only c5300 images in the 11.2(10a)P release. It is expected to be resolved as of 11.2(11)P.

DDTS

To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.

DDTS

Description

CSCdj60533

Back out CSCdj39289, which causes invalid suspend in ARP lookup.

CSCdj39289

Self-generated packet wrongly dropped when sending ARP request.

CSCdj58676

EIGRP redistribution doesn't work when interface flaps.

CSCdj65737

Redistribution into EIGRP fails if protocol routing into same major

CSCdj28874

EIGRP topology entry from redistribute connected does not clear.

CSCdj58853

EIGRP summary routes are not being propagated.

Important Update Note

The code changes committed by CSCdj58676 resolved some issues, but created the symptoms reported in CSCdj65737. The code changes for CSCdj58676 were only committed to releases 11.2(10a), 11.2(10a)BC and 11.2(10a)P, therefore they are the only ones affected by CSCdj65737.

The fix to CSCdj65737 will be to back out the code changes committed by CSCdj58676 and CSCdj28874. That change will have the effect of reintroducing the behavior reported by CSCdj28874. The code back-outs of CSCdj65737 and reintroduction of CSCdj28874 will appear in the following releases:

  • 11.2: 11.2(11), 11.2(11)BC, 11.2(11)P

  • 11.1: 11.1(16), 11.1(16)AA, 11.1(16)CA, 11.1(16)IA

All defect resolution information pertaining to CSCdj58676 is superseded by the details relating to CSCdj65737.

You can avoid the symptoms of CSCdj28874 by specifying only individual networks that are not directly connected to be redistributed into EIGRP instead of using the redistribute connected command.

CSCdj58853 affects only c5300 images in the 11.2(10a)P release. It is expected to be resolved as of 11.2(11)P.

Background

Defect CSCdj60533 has the potential to affect a large portion of the Cisco customer base.The defect occurs only when the Address Resolution Protocol (ARP) lookup routine is invoked and subsequently suspends. The suspend is most likely to occur when an ARP_Reply packet is not immediately received in response to an ARP_Request packet sent by the router. Because conditions (such as the state of an interface) may change while the router resends the ARP_Request and waits for a response, the potential exists for unpredictable results.

Defect CSCdj58676 affects only a subset of the Cisco customer base. Only networks running the EIGRP routing protocol and using route redistribution have the potential of being impacted. Versions affected only by this defect and not CSCdj60533 will not be deferred, and users should consider their exposure to the defect before deploying the affected versions of the software.

Defect CSCdj65737 also only affects networks running the EIGRP routing protocol and using route redistribution. The changes made by CSCdj65737 will be removing code committed by CSCdj28874 and CSCdj58676, thereby reverting back to the less serious behavior described by CSCdj28874. That behavior will be corrected in future releases. See the Field Notice describing releases 11.2(10a), 11.2(10a)BC and 11.2(10a)P for further details.

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:

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