From: Scott Morris (swm@emanon.com)
Date: Sat Dec 30 2006 - 16:17:18 ART
Works fine for me.
interface Loopback0
ip address 10.1.0.0 255.0.0.0
End
emanon-BB1(config-if)#do sh int lo0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 10.1.0.0/8
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation LOOPBACK, loopback not set
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
emanon-BB1(config-if)#
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 Ian
Stong
Sent: Saturday, December 30, 2006 12:48 PM
To: 'Tim'; 'Junk Eva'; ccielab@groupstudy.com
Subject: RE: How 2 Subnet
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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