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Re: OSPF wildcard [7:75371] posted 09/14/2003
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""Zsombor Papp""  wrote in message
news:200309131435.h8DEZtIH006921@xxxxxxxxxxxxxxxxx
> You can use the subnet mask, it will convert to the wildcard (inverting
> bits).

ah, yes, the dumbing down of the IOS. :->

>
> Do you remember why "the recommended practice, at least in the CCIE Power
> Session, is to use the same mask as the interface IP address"? I would
think
> the logical choice in most cases is to use the mask of the AS. That way
the
> exact same single-line command can be used on every router. That's
assuming
> that you want to run OSPF on every single interface, of course.

most folks I know who work large production networks do two things:

a) they number their interfaces such that the same numbers in the 4th octet
are used. preferably the exact same number. e.g. x.x.x.1/ whatever

b) the command they use is network x.x.x.1 0.0.0.0 area y

the reason they tell me is standardization and ease of troubleshooting.

given the dumbing down of the IOS as you mention above, this is probably
less important than in the past.

just as order of network statements used to make a difference, but beginning
( IIRC ) with 12.0 the IOS automatically re-orders the networks statements
into some rational list that makes a lot more sense.

just off hand - do you have any insight as to the source of Cisco's
'recommendation" here? is it based academically, or based on experience
within the Cisco network or large customer networks, for example?


>
> Thanks,
>
> Zsombor
>
> Reimer, Fred wrote:
> >
> > Huh?  The network command uses wildcard mask, not subnet mask.
> > How can
> > "OSPF calculate the wild card mask on its own [given] the
> > subnet mask
> > directly?"  That doesn't make too much sense.
> >
> > OSPF uses the subnet mask on the interface itself, once it
> > determines what
> > interfaces to include.  The wildcard mask used in the network
> > command has
> > nothing to do with the network mask used in advertisements.
> >
> > Fred Reimer - CCNA
> >
> >
> > Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA
> > 30338
> > Phone: 404-847-5177  Cell: 770-490-3071  Pager: 888-260-2050
> >
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> > -----Original Message-----
> > From: Laxmi_Narsaiah [mailto:Narsaiah@xxxxxxxxxx]
> > Sent: Saturday, September 13, 2003 8:47 AM
> > To: cisco@xxxxxxxxxxxxxx
> > Subject: RE: OSPF wildcard [7:75371]
> >
> > Give the subnet mask directly, OSPF calculate the wild card
> > mask on its
> > own....
> >
> > -----Original Message-----
> > From: maine dude [mailto:ciscobloke@xxxxxxxxxxx]
> > Sent: Saturday, September 13, 2003 6:11 PM
> > To: cisco@xxxxxxxxxxxxxx
> > Subject: OSPF wildcard [7:75371]
> >
> >
> > Hi,
> >
> > Just going through some ospf practice, I would like to
> > advertise 3 interfaces 10.60.2.1/23, 10.60.4.1/30 and
> > 10.90.20.10/32. I would go ahead and put the following
> > commands network 10.60.2.1 0.0.0.0 area 0 and
> > 10.60.4.1 0.0.0.0 area 0 and finally 10.90.20.10
> > 0.0.0.0 area 0.
> >
> > However if i wanted get specific subnet information,
> > how would i do that?
> >
> > Thanks in advance,
> >
> > Dj
> >
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