stability of IOS 12.0(5)T1

Hyunseog Ryu/Brookfield/Norlight HRyu at
Thu Nov 18 16:41:39 UTC 1999

Yes, I know, Paul.
But last time when we tried to upgrade to 12.0(7)S,
there was some strange thing happened.
If you read the previous email that I sent, you can understand the
For your convenience, the situation was as follow.
We runned IOS 11.2(12a)P on our Cisco 7507.
For compatability of new hardware, we tried to upgrade IOS to 12.0(7)S.
When we upgraded to 12.0(7)S, there was some abnormal thing happened.
Each traffic from the other interface didn't go through another interface.
Router doesn't work as router. ;<
We tried something, but it didn't work.
So we went back to previous IOS version.
Basically we put both version to flash PCMCIA card memory.
Because of that, it didn't take long time.

After that, I got some responses from you guys.
It was that IOS 12.0 or 11.0.(?)CC has some unstable fact related to
"ip cef" or Routing cache management.


"Paul G. Donner" <pdonner at> on 11/18/99 10:03:33 AM

To:   "Hyunseog Ryu/Brookfield/Norlight" <HRyu at>
cc:    (bcc: Hyunseog Ryu/Brookfield/Norlight)
Fax to:
Subject:  Re: stability of IOS 12.0(5)T1

For stability, the best thing to do is contact the TAC.

However, turning off caching and CEF will force your router into process
switching mode.  Process switching mode is the slowest form of forwarding.

Do you really want to do this?  Then you essentially obviate the need for
the 7500 processing power and the only thing left is the benefit of

You need to look at what features you require and talk with the TAC about
this and then find a stable version (if you haven't already done this)...
basedon the ffeatures you need and the load you put on the box.

Of course, if you don't need the horsepower, then this is a different


At 09:53 AM 11/18/1999 -0600, you wrote:
>Dear folks,
>Thank you for your kind comment about IOS 12.0(7)S.
>I got a lot of response from nanog-pals. :-)
>According to that comment and Cisco's recommend,
>we will try another IOS version, 12.0(5)T1.
>Currently we have Cisco 7507 and 2 physical HSSI interface
>(one is VIP2 module), 3 HSSI software interface (because of VIP2 module).
>And we put the PA-2T3+ card on Cisco 7507 for another connection.
>Problem is that PA-2T3+ can be recognized only by 11.1.(?)CC, 12.0(?)T, or
>12.0(?)S version.
>Cisco guy said that 12.0(?)S version is too early.
>So we will try 12.0(5)T1 on monday morning.
>Our Cisco 7507 has one RSP4 card with 256MB RAM.
>Is there anyone have experience with 12.0(5)T1?
>Is it stable?
>If it is not stable, we have only one option remaining, 11.1(?)CC.
>Please tell me your experiences.
>Basically we will try to turn off "ip cef" and "ip route-cache" option,
>I appreciate your comment.
>Thanks in advance.
>Hyunseog Ryu
>Network Engineer/Applications Engineering
>Norlight Telecommunications, Inc.
>275 North Corporate Drive
>Brookfield, WI 53045-5818
>Tel. +1.262.792.7965
>Fax. +1.262.792.7733

Paul Donner
 Consulting Engineering
 Office of the CTO
 Internet Architecture
ciscoSystems, Inc.


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