Guest

Cisco 2500 Series Routers

Cisco 2520, 2521, 2522, and 2523 Poor SDLC Performance


June 10, 1996


Products Affected

All Cisco 2520, 2521, 2522, and 2523 routers manufactured before May 24, 1996 are subject to this problem.

Problem Description

Cisco Systems has discovered a problem with the Cisco 2520, 2521, 2522, and 2523 routers where the router can experience poor Synchronous Data Link Control (SDLC) performance on the low-speed asynchronous/synchronous serial ports (interfaces Serial 2 to Serial 9). The low-speed asynchronous/synchronous serial interface has trouble maintaining clock synchronization when configured as follows:

  • The interface is configured for encapsulation sdlc-primary or encapsulation sdlc-secondary.

  • The interface is configured for nrzi-encoding.

  • The interface is configured as a DCE.

The low-speed asynchronous/synchronous serial interface may drop SDLC frames with this configuration. The symptoms of this problem are poor performance, dropped sessions, and excessive Cyclic Redundancy Check (CRC) errors on the interface (as shown with the Cisco IOS® Software show interface command).

All Cisco 2520, 2521, 2522, and 2523 routers manufactured before May 24, 1996 are subject to this problem.

Problem Symptoms

The symptoms of this problem are poor performance, dropped sessions, and excessive Cyclic Redundancy Check (CRC) errors on the interface (as shown with the Cisco IOS Software show interface command).

Workaround/Solution

The fix for this problem requires both a hardware revision (00000002) and a software fix (DDTS CSCdi57040 (registered customers only) ), which is incorporated into Cisco IOS Software Releases 11.0(9) and 11.1(4) and later revisions.

To identify whether a router is subject to this problem, you can use one of the following methods:

  • Issue the show interface command. The hardware revisions that are subject to the problem are 00000000 and 00000001. Hardware revision 00000002 contains the hardware fix which resolves this problem:

    cisco 2520 (68030) processor (revision E) with 4096K/2048K bytes of memory.
    Processor board ID 02351913, with hardware revision 00000002
    
  • Open the chassis and examine the motherboard revision number (near the DRAM SIMM socket). The problem revisions and fixed revisions are shown in the table below.

Cisco 2520, 2521, 2522, and 2523 Motherboard Revisions

Product

Problem Revisions

Fixed in Revisions

CISCO2520 with no DRAM on motherboard

800-00590-01

800-00590-02

800-00590-03

CISCO2520 with 2-MB DRAM on motherboard

800-00587-01

800-00587-02

800-00587-03

CISCO2521 with no DRAM on motherboard

800-00589-01

800-00589-02

800-00589-03

CISCO2521 with 2-MB DRAM on motherboard

800-00588-01

800-00588-02

800-00588-03

CISCO2522 with no DRAM on motherboard

800-00592-01

800-00592-02

800-00592-03

CISCO2522 with 2-MB DRAM on motherboard

800-00591-01

800-00591-02

800-00591-02

CISCO2523 with no DRAM on motherboard

800-00593-01

800-00593-02

800-00593-03

CISCO2523 with 2-MB DRAM on motherboard

800-00594-01

800-00594-02

800-00594-03

Note:?The fix for this problem also incorporates the fix for the Cisco 2520 and 2522 router reload problem described in Field Notice: Cisco 2520 and Cisco 2522 Router Reload.

Physical Replacement of Parts

Cisco will provide warranty replacement systems free of charge for these units. To get a warranty replacement Cisco 2520-2523 router, please provide the following information. If you purchased the Cisco 2520-2523 router from a reseller or distributor, contact the reseller or distributor, who will arrange for the replacement hardware. If you purchased the Cisco 2520-2523 router directly from Cisco Systems, you may e-mail this information to swapout@cisco.com or fax it to (408) 526-7118, attention Upgrades Group.

Configuration:

Quantity of Cisco 2520:

Quantity of Cisco 2521:

Quantity of Cisco 2522:

Quantity of Cisco 2523:

Serial Number of each 2520-2523:

Amount of Flash Memory, DRAM on each 2520-2523:

Cisco IOS Software subset and version on each 2520-2523:

Original Sales Order Number:

Original Purchase Order Number (or tracking number):

Your Name:

Your E-mail Address:

Your Phone Number:

Ship To:

Company Name:

Address:

Line 2 Address:

City:

State:

Zip/Postal Code:

Country:

Desired Freight Forwarder/Carrier:

Ship To Contact Name:

E-mail address:

Phone Number:

If you have any questions regarding the replacement program, please contact Cisco Systems Customer Service at (800) 553-NETS or (408) 526-7208 and ask for the Upgrades Group or send e-mail to swapout@cisco.com. If you need technical assistance with the Cisco 2520-2523 router, please contact the Cisco Systems Technical Assistance Centers.

Sincerely,

Cisco Systems

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: