From: Wes Smith (wesmith@rogers.com)
Date: Wed Mar 31 2004 - 15:48:43 GMT-3
There's a few of these gotcha's .
We'd enabled ospf fast hello's on some 7301's. We used 50ms hellos,
with a 1 second dead time.
We expected it to be twitchy, but it worked well, ...
Untill I poped the flash card out of the router...
That caused the box to drop all the ospf adjacencies. due to a file
system bug that hogs CPU for a little to long
It had always done this .. but you didn't know there was a problem until
we configured the fast hellos.
Wes
Richard Dumoulin wrote:
>Ouch !! How did you notice that. Is it demonstrable ?
>
>--Richard
>
>-----Mensaje original-----
>De: McCallum, Robert [mailto:robert.mccallum@thus.net]
>Enviado el: miircoles, 31 de marzo de 2004 17:33
>Para: 'dburnett@click1.net'; Howard C. Berkowitz
>CC: ccielab@groupstudy.com
>Asunto: RE: What IOS really does with commands (was Re: ISIS Problem.
>
>
>Something for you all to note is that many routers and IOS versions when you
>do a wr mem you induce a 350ms
>Outage of traffic flowing through the box. Now some of you may say "big
>deal" but put a voice switch or a time
>Sensitive application and watch it die every time you save the config. Some
>IOS versions now only do this the first
>Time you save the config i.e. just after it is reloaded others still do it
>every time. Also changing the boot system commands induces the same delay
>(there is no way round this).
>
>Robert McCallum
>CCIE #8757 R&S
>01415663448
>07818002241
>
>
>
>>-----Original Message-----
>>From: dburnett@click1.net [mailto:dburnett@click1.net]
>>Sent: 31 March 2004 16:25
>>To: Howard C. Berkowitz
>>Cc: ccielab@groupstudy.com
>>Subject: Re: What IOS really does with commands (was Re: ISIS Problem.
>>
>>
>>Where may someone find more information (as much as may be publicly
>>available) about how IOS creates and stores the data
>>structure that it modifies from entered keywords (aka commands)?
>>
>>----- Original Message -----
>>From: "Howard C. Berkowitz" <hcb@gettcomm.com>
>>To: <ccielab@groupstudy.com>
>>Sent: Sunday, March 28, 2004 9:20 PM
>>Subject: What IOS really does with commands (was Re: ISIS Problem.
>>
>>
>>
>>
>>>At 7:56 AM -0800 3/28/04, Joseph Rinehart wrote:
>>>
>>>
>>>>?Sometimes the router will slightly alter commands in the active
>>>>configuration when you enter them. I had this happen on an
>>>>access-list
>>>>
>>>>
>>last
>>
>>
>>>>week and it nearly drove me crazy at first.
>>>>
>>>>
>>>Something worth knowing to anyone studying for CCIE, but rarely
>>>spelled out specifically, is that the router doesn't just
>>>
>>>
>>record, or
>>
>>
>>>even alter the commands when you enter them -- it
>>>
>>>
>>interprets them and
>>
>>
>>>then throws them away. The earlier courses can give you the
>>>impression that the commands are entered are stored
>>>
>>>
>>somewhere in RAM.
>>
>>
>>>They are not.
>>>
>>>On slower routers, did you ever notice the slight delay
>>>
>>>
>>before "show
>>
>>
>>>running" displays? Show running is essentially a reverse
>>>
>>>
>>compiler or
>>
>>
>>>formatted dump that goes throgh the data structures of the
>>>
>>>
>>router and
>>
>>
>>>creates the configuration statements it thinks would have put the
>>>router into the states reflected by the current values of the data
>>>structures. The delay is due to the significant processing
>>>
>>>
>>involved
>>
>>
>>>in recreating the statements.
>>>
>>>
>>>
>>>>I think this is what is happening, and you would need to
>>>>
>>>>
>>change it by
>>
>>
>>>>specifying Level-1 in the redistribution statement, I believe the
>>>>syntax
>>>>
>>>>
>>is
>>
>>
>>>>"redistribute isis 1 level-1-only metric 4"
>>>>
>>>>
>>>
>>>
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>
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