From: Scott Morris (swm@emanon.com)
Date: Sat Dec 30 2006 - 16:18:27 ART
Say who? It's not your subnet boundary. So while it may confuse some
people (note: people, not routers), there's nothing technically wrong about
it.
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPExpert VP - Curriculum Development
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Ronnie Angello
Sent: Saturday, December 30, 2006 1:02 PM
To: Ian Stong
Cc: Tim; Junk Eva; ccielab@groupstudy.com
Subject: Re: How 2 Subnet
He cited that as a bad example. The .0 is not a legal host address.
10.1.0.0/8 -> ip address 10.1.0.0 255.0.0.0 <- NO GOOD
Ronnie
On 12/30/06, Ian Stong <istong@stong.org> wrote:
>
> HI Tim,
>
> Your fourth example does not make sense to me as it should work fine
> when applying on a router and no error message should be received. You
> are telling the router to assign a network of 10.0.0.0 /8 and then you
> are assigning the interface an IP of 10.1.0.0
>
>
> Just wanted to clarify to avoid confusing "junk eva".
>
> Ian
> www.ccie4u.com
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Tim
> Sent: Saturday, December 30, 2006 8:04 AM
> To: 'Junk Eva'; ccielab@groupstudy.com
> Subject: RE: How 2 Subnet
>
> Hi,
>
> You have the format of the subnet mask incorrect.
>
> When you assign an ip address to an interface, you need to have a 1 in
> the subnet mask for each corresponding bit of the ip address that is
> part of the network portion of the address.
>
> And, you need to have a 0 (zero) in the subnet mask for each bit in
> the ip address that represents the host portion.
>
> So, here are some examples:
>
>
> To assign these addresses to an interface, you would use these commands.
>
> Keep in mind that when you assign an address to an interface, you
> can't assign just the network of the ip address. You must also include
> the host portion of the address.
>
> 172.16.0.1/16 -> ip address 172.16.0.1 255.255.0.0
>
> 192.168.1.1/24 -> ip address 192.168.1.1 255.255.255.0
>
> 192.168.1.1/32 -> ip address 192.168.1.1 255.255.255.255
>
> 10.1.0.0/8 -> ip address 10.1.0.0 255.0.0.0 <- NO GOOD
>
> In the 1st example, the "/16" indicates the 1st 16 bits of the address
> belong to the network portion and the 2nd 16 bits belong to the host
> portion.
>
> In the 2nd example, the 1st 24 bits belong to the network portion
> while the last 8 bits belong to the host portion.
>
> The 3rd example is interesting because it says, in essence, that all
> 32 bits belong to the network portion of the ip address. What this
> means is that the router will have the complete 32 bit address in its
> route table which makes this a host route.
>
> The 4th example is NOT ALLOWED because the host portion of the ip
> address is all 0's. This address only specifies the network portion
> but not the host portion so if you try on a router you'll get an error
> message.
>
> Normally, you don't want to see host routes in the route table because
> then the route table could get way too long. Typically, you only the
> route table to contain just networks.
>
> HTH, Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Junk Eva
> Sent: Friday, December 29, 2006 8:21 PM
> To: ccielab@groupstudy.com
> Subject: How 2 Subnet
>
> Hi,
>
> Can anyone please explain CIDR in detail
>
> can you please explain why the router is showing me this?
>
> R1(config)#int lo 400
> R1(config-if)#ip add 0.0.0.1 0.0.0.0
> Not a valid host address - 0.0.0.1
> R1(config-if)#ip add 1.0.0.1 0.0.0.0
> Bad mask /0 for address 1.0.0.1
>
>
> if
>
> Prefix Length /0
> Netmask 0.0.0.0
> Inverse Netmask 255.255.255.255
> Number of Unique IPs 4,294,967,296
> Number of Class A Networks 256
> Number of Class B Networks 65,536
> Number of Class C Networks 16,777,216
>
> What I'm doing wrong?
>
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