From: Matthew.Sypherd@xxxxxxx
Date: Thu May 31 2001 - 17:50:18 GMT-3
Just thought of something...
If you are concerned that this bug may cause problems in the lab, would
using a wildcard mask of 0.0.0.1 solve this dilemma? (Assuming there are no
other potential interface addresses within that very small range)
This way, we can continue to specify interfaces finely, and possibly avoid
the potential problems of this bug.
I don't have access to my lab right now, so can someone try this out in a
situation where the 0.0.0.0 was not redistributed, or can someone point out
potential problems with this method?
I've been using 0.0.0.0 masks for everything (unless specified otherwise in
the practice lab) and I would like to avoid problems without having to
totally rethink this on the fly. (Yeah, yeah, I know, but... tick
tock...tick tock)
To note, I always do a "o int" (alias exec o show ip ospf ) to verify I
have the correct interfaces defined in my OSPF process. I've caught
multiple omissions and typos with this!
RTP in 2 weeks and counting....My goodness how time flies!!!
Matthew C. Sypherd
CCNP+Security CCDP MCSE CCSE
Jim Graves
<jtg@lucent.c To: Brian Hescock <bhescock@cisco.
com>, "Jeff K." <jeffbk@austin.rr.com>
om> cc: Mike Hess <mahess@home.com>, <
ccielab@groupstudy.com>
Sent by: Subject: Re: 0.0.0.0 wildcard bits
and redistribution
nobody@groups
tudy.com
05/29/2001
08:22 AM
Please
respond to
Jim Graves
I can't think of any reason a 0.0.0.0 wildcard mask should make a
difference either -- but it does. Give it a try. Last night, I set up the
situation Walter talks about, and to my shock and horror he was right. I
used a 0.0.0.0 wildcard mask, and the network didn't show up. When I
changed the network statement to use a 0.0.0.255 wildcard mask, the network
showed up in EIGRP. Huh.
The same thing happens in bootcamp lab 3 if you replace the EIGRP LAN
network with some other network outside 137.20.0.0/16. I tried it with
both 192.168.50.0/24 and 172.20.50.0/24 (to rule out any kind of classful
silliness). Again, when I used 0.0.0.0, the connected network didn't show
up. With 0.0.0.255, it did. The same thing happened when I tried RIP v2
or a second OSPF process instead of EIGRP.
Why? Beats the heck out of me. I tested this using IOS versions 12.0(11),
12.0(15), and 12.0(7)T. I don't know if it's a bug of a feature, but it
sure is weird.
Jim
At 10:35 PM 5/28/2001 -0400, Brian Hescock wrote:
>I can't think of any way using a 0.0.0.0 wildcard bits would affect
>redistribution, unless it's a bug. All the ospf network command does is
>turn on ospf on
>the interface(s) covered by the network statement, that's all it does. It
>has zero effect on the network mask being advertised and no effect on
>redistribution. To everyone that said use a 0.0.0.0 mask (wildcard bits
>actually), thumbs up, it's the preferred method unless you have a lot of
>interfaces you need to turn
>ospf on. Not just for lab use but for production networks as well. Less
>chance for error and easier to troubleshoot.
>
>Brian
>
>On Mon, 28 May 2001, Jeff K. wrote:
>
> > You are exactly right with all the shortcuts. I've never considered
using
> > aliases because I never use them day to day and know that it will wind
up
> > slowing me down since I type pretty fast. I know that I can calculate
a
> > wildcard mask easily and don't have a problem with it. Not my point,
> > though... I was merely asking for an explanation as to why using the
> > 0.0.0.0 area mask would affect route redistribution, which is a
question
> > that hasn't been answered. In my opinion, it makes good common sense
> as you
> > put it to use the 0.0.0.0 mask except when using a wildcard mask that
will
> > allow you to group multiple interfaces into a single area (i.e., a
single
> > statement versus multiple statements). Since I always use logic when
> > assigning my interface addressing schemes, the all 0 mask allows me to
> > double check everything quickly and easily - I know what interface has
what
> > address and where it should be. Not that the wildcard mask makes that
any
> > more difficult - just my personal preference. If a bug or other
> > 'undocumented feature' requires me to use the exact mask, I will be
fine as
> > well... Anyway, if you have an answer for my original question about
why
> > the area mask affects route redistribution (what I originally responded
> to),
> > please respond. I am more curious than anything.
> >
> > Thanks,
> >
> > -Jeff
> > ----- Original Message -----
> > From: "Mike Hess" <mahess@home.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Monday, May 28, 2001 7:06 PM
> > Subject: RE: how anal is the lab grading
> >
> >
> > > Why not just be smart and use a network statement and the right
wildcard
> > > mask for every interface that you are putting into OSPF? It seems
common
> > > sense to me not to try and get too pretty or cut too many corners and
> then
> > > get end up with a problem with 15 minutes left just because you were
too
> > > lazy to be more specific in the first place.
> > >
> > > Some people advocate the use of too many shortcuts. I see a lot of
people
> > > advocating shortcuts such as this, using a whold slew of alias
commands,
> > > etc. Just learn the material and don't try to save seconds when it's
the
> > > minutes and hours that really matter.
> > >
> > > Back to my original point, if you cannot at this point calculate a
simple
> > > wildcard mask then you are going for the wrong certification. Perhaps
it
> > is
> > > not the grading.... :-)
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf
Of
> > > Jeff K.
> > > Sent: Monday, May 28, 2001 5:27 PM
> > > To: Walter Chen; Peter Van Oene; ccielab@groupstudy.com
> > > Subject: Re: how anal is the lab grading
> > >
> > >
> > > You lost me on the second paragraph. Why would using the 0.0.0.0
> > wild-card
> > > mask for interface area identification affect redistribution? This
mask
> > > just allows you to use the interface's address. Obviously the subnet
> mask
> > > of your interfaces will affect redistribution, but I don't see how
the
> > > 0.0.0.0 area mask will. You can definitely mess up your OSPF
topology by
> > > using the wrong mask (i.e., interfaces in the wrong area, interfaces
> added
> > > to OSPF that weren't supposed to be). Let me know what your thoughts
are
> > on
> > > this. Maybe I am forgetting something or am just misunderstanding
> > > something.
> > >
> > > Thanks,
> > >
> > > -Jeff
> > > ----- Original Message -----
> > > From: "Walter Chen" <wchen@iloka.com>
> > > To: "Peter Van Oene" <pvo@usermail.com>; <ccielab@groupstudy.com>
> > > Sent: Monday, May 28, 2001 3:04 PM
> > > Subject: Re: how anal is the lab grading
> > >
> > >
> > > > IMHO, you can use 0.0.0.255 mask if you have other 1.1.1.x/29
networks
> > > onthe
> > > > same router and they also belong to the same OSPF area. However,
if
> > these
> > > > networks should not be in OSPF or in the same area, you definitely
> > should
> > > > not use 0.0.0.255 mask. The absolutely sure and correct way is to
use
> > > > 0.0.0.7 mask for 1.1.1.0/29 network.
> > > >
> > > > You can use 0.0.0.0 mask in cases if you do not need to
redistribute
> > > > 1.1.1.0/29 into other routing protocols on this same router.
However,
> > if,
> > > > say, your 192.168.1.0/24 belongs to EIGRP and you want to
reistribute
> > > > between OSPF and EIGRP, the 1.1.1.0/29 network will NOT be passed
into
> > > EIGRP
> > > > if you have used 0.0.0.0 mask.
> > > >
> > > > Walter
> > > >
> > > > ----- Original Message -----
> > > > From: Peter Van Oene <pvo@usermail.com>
> > > > To: <ccielab@groupstudy.com>
> > > > Sent: Monday, May 28, 2001 9:35 AM
> > > > Subject: Re: how anal is the lab grading
> > > >
> > > >
> > > > > Personally, I'd not use 0.0.0.255 in any case, lab or otherwise.
The
> > > full
> > > > 0's mask is the safe and accurate way to add interfaces to the OSPF
> > > process
> > > > and unless you need to add 20 odd interfaces, I'd suggest you use
it.
> > As
> > > > far as the lab goes, I can attest that lab grading is fair. You
> > shouldn't
> > > > worry about trivial semantics. If your prepared, you'll likely
have a
> > > good
> > > > idea when you are using an illegal shortcut.
> > > > >
> > > > > Pete
> > > > >
> > > > >
> > > > > *********** REPLY SEPARATOR ***********
> > > > >
> > > > > On 5/28/2001 at 7:48 AM Don Dettmore wrote:
> > > > >
> > > > > >Question - How nit-picky are the graders of the lab? F0r
example,
> > > > > >something
> > > > > >occurred to me when I was working in the lab:
> > > > > >
> > > > > >192.168.1.0 /24 ------ R1 ----- 1.1.1.0 /29
> > > > > >
> > > > > >When configuring R1 for OSPF, would the following be acceptable:
> > > > > >
> > > > > >network 1.1.1.0 0.0.0.255 area 0.0.0.0
> > > > > >
> > > > > >Or would that be considered wrong because of the 'wrong' (or I
> should
> > > > say -
> > > > > >not specific enough) wildcard mask.
> > > > > >
> > > > > >Just wondering how anal I must train myself to be.
> > > > > >
> > > > > >Don Dettmore
> > > > > >**Please read:http://www.groupstudy.com/list/posting.html
> > > > > **Please read:http://www.groupstudy.com/list/posting.html
> > > > **Please read:http://www.groupstudy.com/list/posting.html
> > > **Please read:http://www.groupstudy.com/list/posting.html
> > > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
>**Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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