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> 254 IPs

Thu Jan 05, 2012 3:05 pm

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.
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Posts: 232
Joined: Fri Jan 30, 2009 11:41 am
Location: Reading, UK

Re: > 254 IPs

Fri Jan 06, 2012 4:21 am will work normally, id doesn't differ from - you will have 512 normal addresses :).
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Re: > 254 IPs

Wed Jan 11, 2012 5:06 pm

/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
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Re: > 254 IPs

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.
CC_DKP: MTCNA, MTCRE, MTCWE, MTCTCE, part-time packet wrangler

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