dynamic Ip address

[muhammadShareef]

In a company of four deparments we have 24 hosts in each department connectd to a 2950-t switch and each one of the switches is connected to a fifth switch in a (star topology) and IP addresses are configured like this:

1- The first department: subnet mask 255.255.255.224 and ips (192.168.0.1-24) static

2- The seconf department: subnet mask 255.255.255.224 and ips (192.168.0.33-56) static

we were asked to set the IP addresses of the other two departments hosts to be dynamic but we should leave the subnet mask as 255.255.255.224 and the IP addresses (24 in each switch) should continue the sequence of ips from the last switch. 

How can I do that ? 

[David Ruess]

Hello,

You should be able to create a DHCP server on the main switch per subnet and configure an excluded range of the 24 used IPs already.

 ip dhcp excluded-address 192.168.0.1 92.168.0.56 <--this along with other DHCP commands to set it up. But that's how you don't include those IPs in the range. Also don't forget to exclude the IPs you want to use as the default gateway or it will hand it out to a client. Like your post says just exclude everything except the 24 IPs per network you need.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_dhcp/configuration/xe-3se/3850/dhcp-xe-3se-3850-book/config-dhcp-server.html

Or you can add a DHCP sever by itself and do the same thing

Hope that helps

-David

[Joseph W. Doherty]

"You should be able to create a DHCP server on the main switch per subnet and configure an excluded range of the 24 used IPs already."

BTW, what David notes is the way you should do it, but DHCP servers, including those on a Cisco platform, I recall [?] besides checking if an IP has an active, or recently expired lease, also check to see if an IP will respond to an ARP.  I.e. currently active host IPs should also be automatically excluded, but again, not something you should count on for avoiding IP conflicts because if such a host is off-line, DHCP would then lease the IP, and you then would have a conflict won't both hosts are on-line.