Specifications

143
Caveats for Cisco IOS Release 12.0
78-6455-12
Resolved Caveats—Cisco IOS Release 12.0(2)
• CSCdk10762
After a reboot, or CBUS complex restart, there is a small chance (one in several thousand) that one
or more T1s in a CT3 IP will not come back up properly. There are a very specific set of symptoms
for this failure:
– The line comes up at both ends, so all is well physically.
– No T1 alarms or performance monitoring errors are detected.
– The line protocol is down (assuming keepalives are enabled).
– The far-end router counts large numbers of CRC errors in its relevant show interface counters.
– The near-end router (that is, the relevant CT3IP interface) does not show any errors in its
counters.
– The T1 number is 1 through 20 (T1s 21 through 28 are not affected by this problem).
Once in this state, issuing the command microcode reload or reloading the router is the only way
out of this state.
All Cisco IOS releases that support CT3IP have recently been modified to include more details in
the hardware version string displayed in the output of the show controller t3 command. Prior to
firmware version 2.8.0 this display would merely show a H/W Version of 5 as seen in this example:
router# show cont t3 0/0/0
T3 0/0/0 is up.
CT3 H/W Version: 5, CT3 ROM Version: 1.2, CT3 F/W Version: 2.7.0
After upgrading to a Cisco IOS image that includes firmware version 2.8.0 or later, the above
display is enhanced to include more hardware version details as seen in these two examples:
router# show cont t3
T3 0/0/0 is up.
CT3 H/W Version : 5.0.0, CT3 ROM Version: 1.2, CT3 F/W Version: 2.8.0
router# show cont t3
T3 0/0/0 is up.
CT3 H/W Version : 5.0.1, CT3 ROM Version: 1.2, CT3 F/W Version: 2.8.0
Hardware versions 5.0.0 and 5.0.255 are subject to this caveat. Hardware version 5.0.1 is not. (If
you see a hardware version of 5 with no additional numbers, update your software to a more recent
version).
• CSCdk11808
Certain types of terminal adapters (for example, NEC) might toggle many control lines during the
DTR pulsing. These line status changes interrupt the port adapter 8T/4T+ controller and cause a
reset of the line by the IOS driver. Thus the DTR pulse is shortened.
• CSCdk18176
A router with bridging enabled on an ATM Interface (AIP) might continually reboot. A router at
the end of the PVC might fail with a software forced failure. This caveat was first identified in Cisco
IOS Release 11.1(18.1)CA.
• CSCdk31994
Beginning in Cisco IOS Release 11.3(4), a Cisco 4500 router configured for SRB might not remove
IP frames from an FDDI ring. This causes IP frames to circulate around the ring until the TTL
expires. This problem is seen when two or more Cisco 4500 routers are configured for SRB on the
same ring.