Multiple DHCP Servers

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Lusitano
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PostPosted: Fri Sep 23, 2022 3:31    Post subject: Multiple DHCP Servers Reply with quote
Hello, i want to extend my guest bridge to: 192.24.0.1/22 (1024 hosts) .. in 'Multiple DHCP Servers' options, what should i use in 'Max' option ? i tried 1024.. no work, breaks dhcp.
Thx in advance.
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Zyxx
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PostPosted: Fri Sep 23, 2022 8:00    Post subject: Reply with quote
A /22 subnet usually only offers 1022 hosts. The first .0 and the last .255 are reserved values and cannot be used for a host.

Maybe this is the cause for failing DHCP daemon?

/edit

No coffee error...
192.24.x.x isn't a private network!

Following ranges are reserved for private use:

192.168.0.0 - 192.168.255.255 /16
10.0.0.0 - 10.255.255.255 /8
and something arround 172.? - sorry don't know exactly


Anything else behind a NAT, like your 192.24, will result in errors / tears!


Last edited by Zyxx on Fri Sep 23, 2022 8:07; edited 1 time in total
Alozaros
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PostPosted: Fri Sep 23, 2022 8:07    Post subject: Reply with quote
not sure if ddwrt will support that many hosts
on the recent builds dhcp was set in 2 segments
but still 255( /24)is the max if im not wrong… Smile

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kernel-panic69
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PostPosted: Fri Sep 23, 2022 14:21    Post subject: Reply with quote
Wikipedia wrote:


Code:
10.0.0.0/8           10.0.0.0–10.255.255.255         16777216     Private network
172.16.0.0/12        172.16.0.0–172.31.255.255       1048576      Private network
192.168.0.0/16       192.168.0.0–192.168.255.255     65536        Private network


And I think DD-WRT will support any CIDR notation netmask you throw at it. Only one way to find out Twisted Evil Wink

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Lusitano
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Location: São Paulo - Brazil

PostPosted: Fri Sep 23, 2022 17:02    Post subject: Reply with quote
Sorry.. its 192.168, typo, confused with the Max hosts i wrote (5 am, without coffee) Rolling Eyes
I tried use 1022, no work Crying or Very sad Maybe the best way is doing 2 separate brigdes.
dale_gribble39
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PostPosted: Fri Sep 23, 2022 17:50    Post subject: Reply with quote
It's a DD-WRT limitation -and- a dnsmasq limitation:
DD-WRT Help wrote:
Maximum DHCP Users
Enter the maximum number of computers that you want the DHCP server to assign IP addresses to. The absolute maximum is 253, possible if 192.168.1.2 is your starting IP address.

https://thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html
Quote:
-X, --dhcp-lease-max=<number>
Limits dnsmasq to the specified maximum number of DHCP leases. The default is 1000. This limit is to prevent DoS attacks from hosts which create thousands of leases and use lots of memory in the dnsmasq process.

Quote:
Dnsmasq is capable of handling DNS and DHCP for at least a thousand clients.

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Lusitano
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Location: São Paulo - Brazil

PostPosted: Fri Sep 23, 2022 19:10    Post subject: Reply with quote
Right, thank you all for the answers, appreciate Smile
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