[nsp] 7500 insertion force

[Rafi Sadowsky]

 Hi

 Anyone know how "service single-slot-reload-enable" affects the
OIR (75XX) problem ?

 What about 720X OIR experiences ?


 Please see in-line comments below for more detail

-- 
Thanks
	Rafi



Date: Fri, 6 Sep 2002 15:27:31 -0600
From: Clinton Work <work@scripty.com>
To: Cisco-NSP <cisco-nsp@puck.nether.net>
Subject: Re: [nsp] 7500 insertion force


The Cisco 7500 CBUS is shared amoung all the line cards attached
to it. When you do an OIR the bus is electrically interrupted and a
CBUS complex operation is started to rediscover the cards. This usually
means that all packet forwarding stops for 20-30 seconds. If your lucky,
everything comes back and the new card is ready for use. We have run
into a lot of problems with OIR and we now power off our 7513s before swapping
line cards.

CBUS complex:
http://www.cisco.com/warp/public/63/cbus_complex.html
http://www.cisco.com/warp/public/63/top_issues/router_issues/cbus_complex.html

 Quoting from the end of the second URL refernce:

---
How Can I Avoid a Cbus Complex When a VIP Reloads?

 A new feature called Single Line Card Reload (SLCR) has recently been
introduced in Cisco IOSŪ Software version 12.0(13)S. This feature allows
you to only reset the affected line card, as opposed to resetting all the
line cards in the system, which results in a shorter recovery time, and in
a much shorter traffic interruption.

 When this feature is enabled:

  * The affected card first downloads its microcode without blocking the
 traffic between other interface processors.

  * The MEMD is then re-carved. As stated above, this process only takes
 a few seconds. During that time, all traffic is interrupted.

 In summary, traffic interruption lasts around 20 seconds (microcode
download and re-carving) for the affected interface, and just a few
seconds for all other interfaces (compared to two minutes for all the
interfaces in a standard Cbus Complex).
---

 Quoting from:

<http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120limit/120s/120s13/slcr.htm>
---
 Feature Overview

 Before the introduction of the Cisco 7500 Single Line Card Reload
feature, the only method of correcting a line card hardware failure or a severe
software error for one line card on a Cisco 7500 series router required
the execution of a Cbus Complex, a process that reloaded every line card
on the network backplane. The time taken to complete the Cbus Complex was
often inconvenient, and no network traffic could be routed or switched
during the Cbus Complex process.

 The Cisco 7500 Single Line Card Reload feature allows users to correct a
line card failure on a Cisco 7500 series router by automatically reloading
the microcode on a failed line card. During the single line card reload
process, all physical lines and routing protocols on the other line cards
of the network backplane remain active. A single line card reload is also
significantly faster than the Cbus Complex process.
Benefits

Improved Line Card Recovery Time

 The time required to correct a line card hardware failure for one line
card is significantly improved when the Cisco 7500 Single Line Card Reload
feature is enabled. The entire system, which now only reloads one line
card instead of every line card, also experiences a dramatic improvement
in recovery time.

Network Traffic Flow Improvements

 Because the Cisco 7500 Single Line Card Reload feature only reloads the
line card with the hardware failure rather than all of the line cards on
the Cisco 7500 network backplane, the active line cards can continue to
forward network traffic.
---