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> 254 IPs

Posted: Thu Jan 05, 2012 3:05 pm
by sgb32
I’m going to need more than 254 IP addresses so I guess I'll need to configure an RB750 to lease class B IP addresses.

I assume that I configure a Pool of – on the network for example and have DHCP use it.

I’ve never needed this number of IPs before and wondered which is the best way to go about it?

Many thanks.

Re: > 254 IPs

Posted: Fri Jan 06, 2012 4:21 am
by dasiu will work normally, id doesn't differ from - you will have 512 normal addresses :).

Re: > 254 IPs

Posted: Wed Jan 11, 2012 5:06 pm
by karlos
/30 = 4IP
/29 = 8IP
/28 = 16IP
/27 = 32IP
/26 = 64IP
/25 = 128IP
/24 = 256IP
/23 = 512IP
/22 = 1024IP
/21 = 2048IP
/20 = 4096IP
but you cant use the borders so 0 and 255 are not ussable.

so always minus 2

so will give you space for clients from to ( border, Gateway, border)

Or you can also use 2 or more pools so you can use for your DHCP pool1 = and second pool2 = as the "next pool" and the DPHS will give at the first all adresses from pool1 and than from pool2.

If it helps you please give me carma

Re: > 254 IPs

Posted: Wed Jan 11, 2012 7:07 pm
Depending on how / what you are setting up, I would typically set:
/ip address
add address= disabled=no interface=<INTERFACE> network=

/ip pool
add name=DHCP2 ranges=
add name=DHCP1 next-pool=DHCP2 ranges=

/ip dhcp-server
add address-pool=DHCP1 authoritative=yes bootp-support=static disabled=no interface=<INTERFACE> lease-time=1d name=DHCP

/ip dhcp-server network
add address= dns-server= gateway= netmask=23
While you could use a single large DHCP pool, I typically use multiple for two reasons:

1) I have run into some issues from time to time with poorly written clients choking on the .255 and .0 addresses in the middle, so I just avoid handing them out, even if they are technically valid.

2) I like to leave a 5 IP buffer on both sides of a pool, so I have static IP's reserved if I ever need them, and if for some reason I need to split them back into /24's, i don't have to rebuild as much, and keep things consistent. (i always know 1-5 and 250-254 are reserved)

Is it overkill? Probably. Has it worked great for me? Absolutely. Another thought, if this is for a network where you have a lot of turnover (public hotspots, schools, etc), try turning down the lease time to 6-8h and you will find you can stretch an address pool a lot further.