From: Jim Brown (Jim.Brown@xxxxxxxxxxxxx)
Date: Thu Nov 08 2001 - 12:06:03 GMT-3
I thought the real issue with an inverse host mask was something to do with
redistribution or summarization? I can't recall exactly what the bug was,
but it caused some issues when using a host mask opposed to the network
mask. It might be corrected in 12.1?
You are correct though, the address and mask combination only identify
interfaces to participate in the routing process.
The host mask might be considered a lazy way of defining the process. Would
it receive incorrect marks, I don't know? I always use the full network just
for my own clarity.
By the time the lab rolls around you should be able to spout those things
off in your sleep anyways. Subnetting and inverse masking should be natural.
Ohhhhh Wait.... We don't need subnetting skills anymore in the one day lab,
Cisco takes care of that for us.
-----Original Message-----
From: SFeldberg@edeltacom.com [mailto:SFeldberg@edeltacom.com]
Sent: Thursday, November 08, 2001 6:53 AM
To: Ben-Shalom, Omer
Cc: CCIE Groupstudy; Larson, Chris (Contractor); Jason Gardiner;
nobody@groupstudy.com
Subject: RE: CCBootCamp 5 OSPF over frame question
Yes, that's true for point-to-multipoint OSPF network types. I changed the
type on the S1 links between r2 and r4. Note the changes below:
r2#sh ip ospf int s1
Serial1 is up, line protocol is up
Internet Address 10.1.1.2/24, Area 0
Process ID 1, Router ID 20.1.1.1, Network Type POINT_TO_MULTIPOINT, Cost:
64
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
Hello due in 00:00:18
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 10.2.2.2
Suppress hello for 0 neighbor(s)
r2#sh ip route
C 50.0.0.0/8 is directly connected, Loopback0
20.0.0.0/24 is subnetted, 1 subnets
C 20.1.1.0 is directly connected, Ethernet0
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
O 10.2.2.0/24 [110/74] via 10.1.1.4, 00:01:31, Serial1
C 10.1.1.0/24 is directly connected, Serial1
O 10.1.1.4/32 [110/64] via 10.1.1.4, 00:01:31, Serial1
^^^^^^^^^^^^^^
r4#sh ip ospf int s1
Serial1 is up, line protocol is up
Internet Address 10.1.1.4/24, Area 0
Process ID 1, Router ID 10.2.2.2, Network Type POINT_TO_MULTIPOINT, Cost:
64
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
Hello due in 00:00:07
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 20.1.1.1
Suppress hello for 0 neighbor(s)
r4#sh ip route
O IA 50.0.0.0/8 [110/65] via 10.1.1.2, 00:02:31, Serial1
20.0.0.0/24 is subnetted, 1 subnets
O IA 20.1.1.0 [110/74] via 10.1.1.2, 00:02:31, Serial1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
O 10.1.1.2/32 [110/64] via 10.1.1.2, 00:02:31, Serial1
^^^^^^^^^^^^^
C 10.1.1.0/24 is directly connected, Serial1
C 10.2.2.0/24 is directly connected, Ethernet0
r4#
Steve
"Ben-Shalom,
Omer" To: Jason Gardiner
<gardiner@sprint.net>,
<omer.ben-shalom@ "Larson, Chris (Contractor)"
<Chris.Larson@ed.gov>
intel.com> cc: CCIE Groupstudy
<ccielab@groupstudy.com>
Sent by: Subject: RE: CCBootCamp 5
OSPF over frame
nobody@groupstudy question
.com
11/07/2001 06:13
PM
Please respond to
"Ben-Shalom,
Omer"
Do I understand from this that the way you set up the OSPF network statement
makes a difference to the OSPF database and through that to the advertised
routes ?
Never saw any reference to this but if this is the case it is a very
interesting (and important) issue, might have an affect on DDR with OSPF on
demand circuits as well, I'll see if I can get some results on this in the
lab.
Omer.
-----Original Message-----
From: Jason Gardiner [mailto:gardiner@sprint.net]
Sent: Wed, November 07, 2001 11:36 PM
To: Larson, Chris (Contractor)
Cc: 'Ben-Shalom, Omer'; lgao; Courtney Foster; Dennis #6; CCIE Groupstudy
Subject: Re: CCBootCamp 5 OSPF over frame question
OK, I tried to put this to the test. When I configured networks with a host
mask, they show up in the remote routing table as /32s. In order for the
whole network to show up, I had to redist connected subnets. There's to many
variables in this setup. I prefer using the network statement with the mask
of the interface to be injected. It just works better for me.
"Larson, Chris (Contractor)" wrote:
>
> Good point. I never really thought about it that way, but your right
> of course. The network statement simply identifies (in the case of
> OSPF)
which
> interfaces to advertise out of and therefore a host route would work.
>
> Thinking about it like that, I cannot really think of any instances
> where you would not want to , or could not simply use a host route.
> Would
everyone
> agree with that????
>
> Are there instances where you could not?
>
> -----Original Message-----
> From: Ben-Shalom, Omer [mailto:omer.ben-shalom@intel.com]
> Sent: Wednesday, November 07, 2001 3:00 PM
> To: lgao; Courtney Foster
> Cc: Dennis #6; CCIE Groupstudy
> Subject: RE: CCBootCamp 5 OSPF over frame question
>
> The OSPF network statement really has nothing to do with networks it
> is
an
> access list (and that is why it uses the mask the way it does) to
> filter
the
> interfaces to take part in OSPF, you COULD use the right network mask
> for the interfaces or not, that is really a style issue. A while back
> I asked the same thing stating that I personally prefer the network
> mask to a host mask but later was convinced by a number of good people
> that unless you have a big router with many interfaces using the
host
> mask is cleaner and less prone to mistakes and surprises so I am now
using
a
> host mask.
>
> Again - both will work and this is really a style issue nothing more.
>
> Omer.
>
> -----Original Message-----
> From: lgao [mailto:lgao@cisco.com]
> Sent: Wed, November 07, 2001 7:57 PM
> To: Courtney Foster
> Cc: Dennis #6; CCIE Groupstudy
> Subject: Re: CCBootCamp 5 OSPF over frame question
>
> I don't think it is the best practice to advertise a host mask, it
> looks like a lazy thing that dont' want to figure out what the true
> mask is.
>
> Courtney Foster wrote:
>
> > It is a host specific mask....because you don't have broadcast...you
are
> > telling OSPF that this host is Area 10...At least that's what I
> > think
> >
> > -----Original Message-----
> > From: Dennis #6 [mailto:vacant@home.com]
> > Sent: Wednesday, November 07, 2001 12:04 PM
> > To: CCIE Groupstudy
> > Subject: CCBootCamp 5 OSPF over frame question
> >
> > I noticed on the CCBootCamp lab 5 solution that the wildcard mask on
> > each router for the point-to-multipoint frame connections is 0.0.0.0
> > (see below). Is there a good reason for using this mask as opposed
> > to 0.0.0.255 (it's a /24 subnet)? When is it best to use 0.0.0.0
> > versus 0.0.0.255. I thought it was normal to use the inverse mask
> > that corresponds to the subnet mask on that interface. What am I
> > missing?
> >
> > router ospf 1
> > redistribute igrp 1 metric 20 metric-type 1 subnets network
> > 172.168.100.5 0.0.0.0 area 10 !point to multipoint frame connection
> > network 137.20.20.0 0.0.0.255 area 0 area 10 virtual-link
> > 172.168.30.97 area 10 virtual-link 172.168.100.6
> >
> > Thanks,
> >
> > Dennis #6
-- Thanks,Jason Gardiner Supervisor, Engineering Services Sprint <Insert Division Name>
"You can swim all day in the Sea of Knowledge and still come out completely dry. Most people do."
- Norton Juster
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