IP/Subnetting Questions

staffordscott

Hey all,

First, I apologize if this is the wrong forum for this particular question. I looked around and did not see a Packet Tracer sub board. I'm working on my final project for my first semester CCNA class, and it's a packet tracer activity. I've finally gotten my head wrapped around the basics of IP routing and Subnetting, but my head is spinning with this particular part of the project.

In the large network we're building, we're working off the allocated address range of 10.10.64.0 /21. We are suppose to be subnetting into the various sizes needed for this particular network as stated in our instructions/addressing table. Maybe it's the wording that's tripping me up, or maybe I'm over thinking this, but I just need some direction.

There are three networks within the one address, Phoenix, Chicago, and Bangor. Listed with each city name is a summary of the information already given to me, ex:

Phoenix
#of hosts needed 416
#of addresses allocated 512
CIDR /23
Subnet Address 10.10.68.0
1st host n/a
Last Host n/a
Broadcast n/a
Subnet Mask 255.255.254.0

Under that information is another table, listing information for Phoenix-Lan-1, as follows:

PHX-Lan-1
#of hosts needed 25
#of addresses allocated 32
CIDR /27
Subnet Address 10.10.69.128
1st Host .69.129
Last Host .69.158
Broadcast .69.159
Subnet Mask 255.255.255.224

From there, for Phoenix LAN's 2 & 3, I need to fill out the table myself. I'm getting confused trying to figure out where the different Subnet Addresses are coming from (i.e. 10.10.64.0 /21 vs. 10.10.68.0 /23 vs. 10.10.69.128 /27), and are these the equivalent of an IP address for the subnet? It's my understanding, that the first three octets are for the network, with the fourth octet being for the host ID. My biggest problem is that I'm getting confused with what the definition of a subnet address and subnet mask are. I know how to find the Subnet mask by using the CIDR, but I'm not sure if I am using subnetting tables correctly to answer the questions.

I'm currently looking at trying to solve the info for PHX-LAN-2, and have the following in bold solved (I think):

PHX-LAN-2
#of hosts needed 150
#of addresses allocated
CIDR /24
Subnet Address
1st host
Last Host
Broadcast
Subnet Mask 255.255.255.0

Now, am I correct that in order to find the missing information, I should be using a Class-B subnetting table? I've been watching Youtube videos on Class C and Class B tables and trying my damnedest to make sense of them, but I don't know if I'm understanding them 100% yet. If I am making sense of them, then the following info I imagine is correct when looking at a Class-B table:

Bit value 1
256 - 2 networks
256 - 2 hosts
/24

Again, if I am right, I have no idea how to pull subnet addresses from that and if it is indeed suppose to be different from the Phoenix summary address and PHX-LAN-1 address.

---

Sorry for the long winded post, but I've been racking my brain around this for the last day or so and can't seem to make sense of it. I'm sure it's easier than I've made it up to be in my mind, but some direction would be appreciated. I can also answer more questions if more information is needed.

Thanks everyone!

EdTheLad

staffordscott wrote: »

address range of 10.10.64.0 /21.
Phoenix
#of hosts needed 416

PHX-Lan-1
#of hosts needed 25

PHX-LAN-2
#of hosts needed 150

Pheonix
416 hosts => /23

10.10.64.0/23 range 10.10.64.0 -> 10.10.65.255 ; 64.0 = subnet; 65.255 = broadcast for subnet
Above shows the range of host addresses if i was to use a /23 only, but this /23 can be broken up further.


Now i will look at 10.10.64.0/23 as being my allocated range which needs to be broken up into LAN-1 & LAN-2

Lan-1 25 hosts i.e. /27
10.10.64.0/27
Lan-2 150 hosts i.e. /24
10.10.65.0/24

Now if you look at what's left from original range 10.10.64.0/23 i.e. 10.10.64.0 -> 10.10.65.255

10.10.65.0/24 ; previously allocated
10.10.64.0/24; partially available, already allocated .0/27

The /24 contains 8 x /27's
i.e.
10.10.64.0/27 alocated
10.10.64.32/27 available
10.10.64.64/27 available
" "
" "
" "
10.10.64.224/27 available