ip , network address , subnet mask basics

sumeet inani · 05-09-2014, 07:35 AM

we have a cisco catalyst network switch in our lab
I want to use ip 172.16.200.something to create two separate networks
I tried to use following

Code:

#sh int vlan 280
Vlan280 is up, line protocol is up
  Hardware is EtherSVI, address is 588d.090e.597f (bia 588d.090e.597f)
  Internet address is 172.16.200.241/28
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:23:23, output 00:24:03, 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: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     180 packets input, 18123 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     8 packets output, 1640 bytes, 0 underruns
     0 output errors, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out

This works.
here I have set subnet mask 255.255.255.four-ones-four-zeros
Now I am unable to think of another network ?

acid_kewpie · 05-09-2014, 08:08 AM

Quote:

255.255.255.four-ones-four-zeros

?? what on earth does that mean?

why do you need to "think" of another network, you would just use an appropriate network mask. if you want to split a /24 into two halevs, then the mask would be a /25. You don't memorize binary strings.

sumeet inani · 05-09-2014, 08:17 AM

OK , I could not clarify myself in my first post.

Current configuration is

Code:

gpon1#sh runn int vlan 280
Current configuration : 68 bytes
!
interface Vlan280
 ip address 172.16.200.241 255.255.255.240
end
ip dhcp pool vlan280
   network 172.16.200.240 255.255.255.240
   dns-server 196.1.105.47
   default-router 172.16.200.241
!

gpon1#sh runn int vlan 281
Current configuration : 66 bytes
!
interface Vlan281
 ip address 172.16.200.1 255.255.255.240
end


ip dhcp pool vlan281
   network 172.16.200.0 255.255.255.240
   dns-server 196.1.105.47
   default-router 172.16.200.1
!

I am hoping that this will give IP 172.16.200.242-255 for those with vlan 280.
This happens.
Also , I hope that those with vlan 281 will get IP 172.16.200.2-15
This does not happen ?

sumeet inani · 05-11-2014, 11:33 PM

Is that understandable ?
Where am I wrong in my settings ?