Need reasurance with VLSM

Dan-HumphreysDan-Humphreys Posts: 20Member ■□□□□□□□□□
I have the use of 172.20.0.0/22 and 172.20.4.0/22 I must subnet these addresses down and this is the table I have created. Can anybody reasure me that it is correct?



Network Area

No. Users / IPs


VLSM block size / No. of IPs (powers of 2)




HQ Network

112

172.20.4.0 255.255.255.128



RO1 Network

200

172.20.3.0 255.255.255.0



RO2 Network / VLANs




VLAN 1 (Server Farm)

18 users

172.20.2.64 255.255.255.224



VLAN 2 (Native/mgmt -IP)

9 users

172.20.2.96 255.255.255.240



VLAN 11 (Dept 1)

75 users

172.20.1.128 255.255.255.128



VLAN 12 (Dept 2)

112 users

172.20.1.0 255.255.255.128



VLAN 13 (Dept 3)

38 users

172.20.2.0 255.255.255.192



VLAN 101 (wireless)

52 users

172.20.1.192 255.255.255.192



WAN link (RO2 to HQ)

2

172.20.2.112 255.255.255.252



Total users and block sizes for RO2

306

172.20.0.0 255.255.254.0



RO2 block size to subdivide

N/A




Total users and all VLSM blocks

618



Comments

  • jukemjukem Posts: 33Member ■■□□□□□□□□
    Looks correct to me.
    “You got a dream, you gotta protect it. People can’t do something themselves, they wanna tell you, you can’t do it. If you want something, go get it. Period.”--Will Smith in the Movie: Pursuit of Happyness
  • pheobopheobo Posts: 2Registered Users ■□□□□□□□□□
    At first glance looks like the block for RO2 is the right size, but there is an error.

    172.20.0.0 255.255.254.0 = 172.20.0.0/23
    You usable range for this mask is:
    172.20.0.0 - 172.20.1.255

    You have several addresses from 172.20.2.X in your R02 block. They don't fit the address allocation you gave that area.

    I have not checked any further.
  • jukemjukem Posts: 33Member ■■□□□□□□□□
    Oops phoebo is correct. Your mask for the RO2 network must be 255.255.252.0 for a usable range of 172.20.0.0 - 172.20.3.255 unless the zero subnet is usable.
    “You got a dream, you gotta protect it. People can’t do something themselves, they wanna tell you, you can’t do it. If you want something, go get it. Period.”--Will Smith in the Movie: Pursuit of Happyness
  • inscom.brigadeinscom.brigade Posts: 400Member
    172.20.0.0/22 has 1022 host, 1020 usable, and 64 subnets available.

    I am re doing my math
    edit:
    dang it, to bad, i should not have had that drink, haha.
    now i have dirt on my face.

    Oh well it is Friday night and I worked hard this week, I am going to play a video game F, VLSM tonight!



    Edit

    172.20.0.0...... 172.20.0.3/30 2 user
    172.20.0.4...... 172.20.0.15/28 10 user
    172.20.0.16......172.20.0.31/27
    172.20.0.32 .....172.20.0.127/25
    172.20.0.128....172.20.0.191/26
    172.20.0.192....172.20.0.255/25
    172.20.1.0........172.20.0.127/25
    172.20.1.128.....172.20.1.255/25
    172.20.2.0....... 172.20.2.255/24
    172.20.3.0....... 172.20.3.255/23
    I am thinking that this could work, as you see from above it is friday night after a couple.
    I might be eating Crow in the Morning
  • Dan-HumphreysDan-Humphreys Posts: 20Member ■□□□□□□□□□
    Thanks to everyone for the advise, I see my mistake was calculating the RO2 address before the VLAN's. What I had done was calculated the RO2 network with the consideration for 306 users that led me to the mask of /23. After realising my mistake I see why it would not work, as there are over used host bits on every vlan which leads to the requirement of over 510.
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