IPAddress Reservation (Best Practice)
Luis Fernando Lacayo
lflacayo at cps.k12.il.us
Mon Aug 11 13:26:19 UTC 2008
Thank for the quick response...
You are correct, I meant "Fixed address assignments"... That is what I
get from hanging around windows people.
Please see my comments/questions below.
On Mon, 2008-08-11 at 13:57 +0100, Simon Hobson wrote:
> Luis Fernando Lacayo wrote:
>
> >I have a quick question, I have a bunch of subnets and I have DHCP
> >Lease reservations for almost every network.
>
> First off, I assume you mean "fixed address assignments" - lease
> reservations are a bit of Windows terminology, different method of
> working and plenty of scope for confusion !
>
> > my question is about how to define these reservations. currently
> >I have each reservation under its own subnet. I have seen some
> >configuration files that just bundles them at the end of the file.
> >I imagine that this works.
>
> They MUST NOT be within a subnet declaration. With a few exceptions
> for some rather unusual requirements, you REALLY do not want them in
> your subnet declarations. Host statements are global in scope (and so
> are still 'valid' when the client is not in that subnet - BUT,
> clients matching a host statement will inherit some options from the
> subnet where the host declaration is made.
>
OK, I think I understand. Will this apply to the failover configuration
as well?
So this setup would be incorrect:
## Third Floor South Wired
subnet 10.129.76.0 netmask 255.255.254.0 {
option routers 10.129.76.1;
...
option broadcast-address 10.129.77.255;
option domain-name-servers 10.129.161.20, 10.128.5.28;
option subnet-mask 255.255.254.0;
......
pool {
failover peer "co-wan03";
deny dynamic bootp clients;
allow unknown-clients;
range 10.129.76.21 10.129.76.230;
range 10.129.77.21 10.129.77.230;
}
## Anthony James
host Host-10.129.76.225 {
hardware ethernet 00:0d:56:a0:67:c4;
fixed-address 10.129.76.225;
}
}
## Fourth Floor Wired
subnet 10.129.78.0 netmask 255.255.254.0 {
option routers 10.129.78.1;
...
option broadcast-address 10.129.79.255;
option domain-name-servers 10.129.161.20, 10.128.5.28;
option subnet-mask 255.255.254.0;
....
pool {
failover peer "co-wan03";
deny dynamic bootp clients;
allow unknown-clients;
range 10.129.78.21 10.129.78.230;
range 10.129.79.21 10.129.79.230;
}
host Host-10.129.78.232 {
hardware ethernet 00:20:6b:51:db:45;
fixed-address 10.129.78.232;
}
It should be:
## Third Floor South Wired
subnet 10.129.76.0 netmask 255.255.254.0 {
option routers 10.129.76.1;
...
option broadcast-address 10.129.77.255;
option domain-name-servers 10.129.161.20, 10.128.5.28;
option subnet-mask 255.255.254.0;
......
pool {
failover peer "co-wan03";
deny dynamic bootp clients;
allow unknown-clients;
range 10.129.76.21 10.129.76.230;
range 10.129.77.21 10.129.77.230;
}
}
## Fourth Floor Wired
subnet 10.129.78.0 netmask 255.255.254.0 {
option routers 10.129.78.1;
...
option broadcast-address 10.129.79.255;
option domain-name-servers 10.129.161.20, 10.128.5.28;
option subnet-mask 255.255.254.0;
....
pool {
failover peer "co-wan03";
deny dynamic bootp clients;
allow unknown-clients;
range 10.129.78.21 10.129.78.230;
range 10.129.79.21 10.129.79.230;
}
}
## Anthony James
host Host-10.129.76.225 {
hardware ethernet 00:0d:56:a0:67:c4;
fixed-address 10.129.76.225;
}
## James Brown
host Host-10.129.78.232 {
hardware ethernet 00:20:6b:51:db:45;
fixed-address 10.129.78.232;
}
> In case you haven't worked that out, you can have a client getting a
> dynamic IP address in one subnet, while inheriting the (incorrect)
> router address from the subnet where it's host statement is declared.
> I think anyone can imagine the confusion that could cause !
I have not ran into this issue yet. but it could create
>
> >I am working on a small interface to to manage these because they
> >are getting out of control, with staff members moving floors and
> >printers being removed or relocated...
> >
> >How are you defining your reservations? and better yet how are you
> >managing them?
>
> Many people store the information in a database (it can be anything
> you are comfortable with), and then have a routine that will extract
> the data and build a config file. You only need to build parts of a
> file - for example you can just build a file with host declarations
> and use the 'include" statement to include it in the main config file.
>
Any special program (Open source) that you recommend?
Thanks again,
Luis
--
Luis Fernando Lacayo
Chicago Public Schools
Senior Unix Administrator
ITS/ UNIX Infrastructure
Office: 773-553-3835
Cell: 773-203-4493
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