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Cisco IOS Software Releases 12.1 Mainline

Field Notice: NAT Issues with Cisco IOSý Software Release 12.1(4)


September 23, 2000



Products Affected

Product

Comments

Cisco IOS Software Release 12.1(4)

?

Problem Description

When a Network Address Translation (NAT) router is configured with Address Overload, any application traffic going through this NAT router with embedded address and port information may not work. This problem has been noted in Cisco IOS Software Releases 12.1(3.4) and higher.

The following applications are affected:

  • File Transfer Protocol (FTP)

  • Trivial File Transfer Protocol (TFTP)

  • NetMeeting

  • Streamworks

  • RealAudio

  • NBSS

  • VDOLive

  • VXtreme

Background

The root cause is that the FTP ls command (see Cisco bug ID CSCds15078 below) stops responding over the NAT router.

Problem Symptoms

Sample Configuration

e0 e1
ftp-Client ----- NAT Router --------- ftp-Server
1.0.0.1 in out 2.0.0.2

NAT Sample Configuration 1

int Ethernet0
ip nat inside
     
int Ethernet1
ip nat outside
     
ip nat inside source list 1 pool pool1 overload
ip nat pool pool1 2.0.0.5 2.0.0.10 netmask 255.255.255.0
access-list 1 permit 1.0.0.1

NAT Sample Configuration 2

 int ethernet0
     ip nat inside
     
     int ethernet1
     ip nat outside
     
     ip nat inside source list 1 interface Ethernet1 overload
     access-list 1 permit 1.0.0.1

Workaround/Solution

The fix for this defect has been integrated into Release 12.1(4.1) and is subsequently available in Release 12.1(5). Release 12.1(4.1) is an interim release available only from the Cisco TAC.

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

CSCds15078

FTP ls command hangs over NAT.

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: