From: Mark Lewis (markl11@xxxxxxxxxxx)
Date: Tue Feb 13 2001 - 23:44:54 GMT-3
Hi,
Looks like you're getting some good feedback from list members. In addition,
you might like to take a look at 'Enhanced IP Services for Cisco Networks'
(Cisco Press) which has a very nice explanation of VLSM and summarization
plus associated issues in ch.1. The rest of the book is pretty good too -
answered some of the nagging questions I had before my lab.
Hope that helps,
Mark
CCIE#6280 / CCSI#21051
>From: "fwells12" <fwells12@hotmail.com>
>Reply-To: "fwells12" <fwells12@hotmail.com>
>To: <ccielab@groupstudy.com>
>Subject: Re: IP addressing thoughts...
>Date: Tue, 13 Feb 2001 13:38:47 -0800
>
>I appreciate your feedback Fred. Solid advice. One thing I did not quite
>grasp was your statement 'I would space my subnets acccordingly for all
>routers' would you be kind enough to elaborate on what you meant by it
>please.
>
>----- Original Message -----
>From: Fred Ingham <fningham@worldnet.att.net>
>To: frank wells <fwells12@hotmail.com>; <ccielab@groupstudy.com>
>Sent: Tuesday, February 13, 2001 11:13 AM
>Subject: Re: IP addressing thoughts...
>
>
> > Frank: The basic idea is sound but before you assign a given range to a
> > router I suggest you read the instructions for any fixed addresses. If
> > there is a required loopback of 172.16.225.0/30 on r2, for instance,
> > your scheme falls apart.
> >
> > I suggest ranges of 32 rather than 16 (will work for 8 routers) and also
> > space out the networks to the lowest mask requested. For instance if
> > there is a required network of /22 somewhere in the network I would
> > space my subnets acccordingly for all routers. This guarantees no
> > overlaps.
> >
> > There are no points in the lab for saving address space. You should
> > complete your addressing before configuring the routers and also draw a
> > network diagram. Going into the lab with a fixed addressing scheme can
> > cost you time. Rather, you should be able to construct addressing
> > quickly after reading the requirements. On rebooting - in the lab I
> > recommend you do this often - there are no points for not rebooting and
> > it can
> > clear up nagging problems.
> >
> > My opinion, Fred.
> >
> > frank wells wrote:
> > >
> > > I am giving a little thought to how I am going to handle the IP
>addressing
> > > in the lab. Regardless of the IP address/mask I am given I want to
>come
>up
> > > with a scheme which allows me easy summarization of all routers and
>their
> > > connected OSPF network segments.
> > >
> > > I am almost certain Cisco will throw the VLSM-FLSm issues at me and I
>want
> > > to be prepared.
> > >
> > > Lets say we get the following address/mask given to use: 172.16.0.0
>and
>we
> > > are able to cut it up any way we want.
> > >
> > > Give me your thoughts on the following idea:
> > >
> > > 172.16.0.0 use mask 255.255.240.0 to get 14 useable subnets (not
>including
> > > subnet zero) I chose the 24 bit subnet mask to anticipate being given
> > > possible RIP/IGRP FLSM addresses to
> > > deal with. I assign a contiguous range of subnets to each router like
>so:
> > >
> > > R1=172.16.16.0 - 172.16.31.0
> > > R2=172.16.32.0 - 172.16.47.0
> > > R3=172.16.48.0 - 172.16.64.0
> > > R4=172.16.64.0 - 172.16.71.0
> > > R5=172.16.72.0 - 172.16.87.0
> > > R6=172.16.88.0 - 172.16.95.0
> > > R7=172.16.96.0 - 172.16.111.0
> > > R8=172.16.112.0 - 172.16.127.0
> > >
> > > Now when asked to do something like intra-area summarization to the
>max,
>I
> > > can easily summarize each routers connected networks with a simple
>command
> > > like area 1 range 172.16.16.0 255.255.240.0 right?
> > >
> > > Also, by planning this way I would like to be able to address my
>network
> > > before I begin typing it into the routers. This would give me an
>advantage
> > > as I would be able to assign the highest IP addresses in the
>respective
> > > subnets to a/the loopback addresses etc. Ultimately I want to not
>have
>to
> > > reboot the routers because I created an OSPF adjacency prior to adding
>the
> > > loopbacks etc.
> > >
> > > I am also thinking about drawing a line on top of my picture and
>deviding it
> > > into as many segemnts as I have routers like so:
> > >
> > > R1 R2 R3 R4 R5 R6 R7 R8
> > > |-------|-------|-------|-------|-------|-------|-------|-------|
> > > 16 32 48 64 72 88 96 112 127
> > >
> > > By doing this I can easily mark off along my line which subnets I have
> > > already used too which may prove to be useful. Plus, it takes up
>little
>to
> > > no room on your paper.
> > >
> > > Hope the ASCII pic isn't mangled too bad...
> > >
> > > Good idea/bad idea?, thoughts please.
> > >
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