Date: Thu, 15 Sep 2005 08:56:39 -0400 (EDT) From: Jerry McAllister <jerrymc@clunix.cl.msu.edu> To: gpeel@thenetnow.com Cc: freebsd-questions@freebsd.org, John Oxley <john@yoafrica.com> Subject: Re: IPs , Netmasks and Broadcast. Message-ID: <200509151256.j8FCudQ7008772@clunix.cl.msu.edu> In-Reply-To: <002d01c5b9f3$439f9310$6501a8c0@GRANT>
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> > Thanks John, > > What you are saying make perfect sense based on what I've had to do in the > past. Just to clarify ... > > Lets say I have 5 machines (which I do) > > And lets say I have 10 blocks of IP address from my upline (which I do) > > 1.1.1.1/24 > 2.2.2.2/24 > 3.3.3.3/24 > 4.4.4.4/24 > ... > > And, lets say that I need to set up various IPs, from each of the groups > above, on all 5 of the servers. > > To keep the explanation easy to follow, I will put what I might have in > rc.conf for each machine, Leaving out the gateway IPs as they are not > realevent to the question...my router setting work fine. No, this is not what I said. I don't know if anyone else has posted on this since then. But, The next two chunks below represent what I said. ////jerry Sever 1: hostname="machine1.mydomain.com" defaultrouter="some ip here" ifconfig_em0="inet 1.1.1.2 netmask 255.255.255.0" ifconfig_em0_alias0="inet 1.1.1.3 netmask 255.255.255.255" ifconfig_em0_alias1="inet 1.1.1.4 netmask 255.255.255.255" ... ifconfig_em0_alias2="inet 2.2.2.3 netmask 255.255.255.255" ifconfig_em0_alias3="inet 2.2.2.4 netmask 255.255.255.255" ifconfig_em0_alias4="inet 2.2.2.5 netmask 255.255.255.255" ... ifconfig_em0_alias5="inet 3.3.3.4 netmask 255.255.255.255" ifconfig_em0_alias6="inet 3.3.3.5 netmask 255.255.255.255" ifconfig_em0_alias7="inet 3.3.3.6 netmask 255.255.255.255" ... Sever 2: hostname="machine2.mydomain.com" defaultrouter="some ip here" ifconfig_em0="inet 1.1.1.5 netmask 255.255.255.0" ifconfig_em0_alias0="inet 1.1.1.6 netmask 255.255.255.255" ifconfig_em0_alias1="inet 1.1.1.7 netmask 255.255.255.255" ... ifconfig_em0_alias2="inet 2.2.2.6 netmask 255.255.255.255" ifconfig_em0_alias3="inet 2.2.2.7 netmask 255.255.255.255" ifconfig_em0_alias4="inet 2.2.2.8 netmask 255.255.255.255" ... ifconfig_em0_alias5="inet 3.3.3.7 netmask 255.255.255.255" ifconfig_em0_alias6="inet 3.3.3.8 netmask 255.255.255.255" ifconfig_em0_alias7="inet 3.3.3.9 netmask 255.255.255.255" ... ----------------------------------------------------------------- Sever 1: > > hostname="machine1.mydomain.com" > defaultrouter="some ip here" > ifconfig_em0="inet 1.1.1.2 netmask 255.255.255.0" > ifconfig_em0_alias0="inet 1.1.1.3 netmask 255.255.255.255" > ifconfig_em0_alias1="inet 1.1.1.4 netmask 255.255.255.255" > ... > ifconfig_em0_alias2="inet 2.2.2.3 netmask 255.255.255.0" > ifconfig_em0_alias3="inet 2.2.2.4 netmask 255.255.255.255" > ifconfig_em0_alias4="inet 2.2.2.5 netmask 255.255.255.255" > ... > ifconfig_em0_alias5="inet 3.3.3.4 netmask 255.255.255.0" > ifconfig_em0_alias6="inet 3.3.3.5 netmask 255.255.255.255" > ifconfig_em0_alias7="inet 3.3.3.6 netmask 255.255.255.255" > ... > > > Sever 2: > > hostname="machine2.mydomain.com" > defaultrouter="some ip here" > ifconfig_em0="inet 1.1.1.5 netmask 255.255.255.0" > ifconfig_em0_alias0="inet 1.1.1.6 netmask 255.255.255.255" > ifconfig_em0_alias1="inet 1.1.1.7 netmask 255.255.255.255" > ... > ifconfig_em0_alias2="inet 2.2.2.6 netmask 255.255.255.0" > ifconfig_em0_alias3="inet 2.2.2.7 netmask 255.255.255.255" > ifconfig_em0_alias4="inet 2.2.2.8 netmask 255.255.255.255" > ... > ifconfig_em0_alias5="inet 3.3.3.7 netmask 255.255.255.0" > ifconfig_em0_alias6="inet 3.3.3.8 netmask 255.255.255.255" > ifconfig_em0_alias7="inet 3.3.3.9 netmask 255.255.255.255" > ... > > Sever 2: > > hostname="machine3.mydomain.com" > defaultrouter="some ip here" > ifconfig_em0="inet 1.1.1.8 netmask 255.255.255.0" > ifconfig_em0_alias0="inet 1.1.1.9 netmask 255.255.255.255" > ifconfig_em0_alias1="inet 1.1.1.10 netmask 255.255.255.255" > ... > ifconfig_em0_alias2="inet 2.2.2.9 netmask 255.255.255.0" > ifconfig_em0_alias3="inet 2.2.2.10 netmask 255.255.255.255" > ifconfig_em0_alias4="inet 2.2.2.11 netmask 255.255.255.255" > ... > ifconfig_em0_alias5="inet 3.3.3.10 netmask 255.255.255.0" > ifconfig_em0_alias6="inet 3.3.3.11 netmask 255.255.255.255" > ifconfig_em0_alias7="inet 3.3.3.12 netmask 255.255.255.255" > ... > > Server 3, 4 and 5 similar with repeating patterns. > > So the original question was: When setting up an IP from any given block, > do, or should I, need to use the real netmask that my ISP has assinged me > (for the first), then, the single host (255) netmask for each of the rest > (Again, from a specific IP block? > > I hope it is because I have hundreds of IPs set up that way. > > The reason I ask this question (again) is because I have one IP that does > not want to work using the above paradigm. That is to say, that it IS the > only IP from a specific block, on a particular machine, and it won't take > using the real netmask, it will only work using the 255 netmask. > > Sincerly, > > -Confused > (Grant). > > > > > > > > ----- Original Message ----- > From: "John Oxley" <john@yoafrica.com> > To: "Grant Peel" <gpeel@thenetnow.com> > Cc: <freebsd-questions@freebsd.org> > Sent: Thursday, September 15, 2005 7:55 AM > Subject: Re: IPs , Netmasks and Broadcast. > > > > On Wed, Sep 14, 2005 at 12:00:12PM -0400, Grant Peel wrote: > >> Now I am really confused. > > First of all install ipcalc NOW. > > > >> Up until this morning I thought I had a good handle on when I need to use > >> the real Netmask and Broadcast. > >> > >> For example, If I have 3 servers, and my upline asigns me a block of 128 > >> addresses, for the first ip used (from this block) on each server, I > >> would > >> need to specify the IP, true netmask and a broadcase. Then, when using > >> more > >> IPs from that block, I would use a 255.255.255.255 netmask and a > >> broadcast > >> equal to the IP. > > > > No, a 255.255.255.255 netmask specifies a single host. If your ISP has > > given you 128 IPs, that is a /25 or netmask 255.255.255.128 as shown : > > sysjo@hades:~$ ipcalc 192.168.254.0/25 > > Address: 192.168.254.0 11000000.10101000.11111110.0 0000000 > > Netmask: 255.255.255.128 = 25 11111111.11111111.11111111.1 0000000 > > Wildcard: 0.0.0.127 00000000.00000000.00000000.0 1111111 > > => > > Network: 192.168.254.0/25 11000000.10101000.11111110.0 0000000 > > HostMin: 192.168.254.1 11000000.10101000.11111110.0 0000001 > > HostMax: 192.168.254.126 11000000.10101000.11111110.0 1111110 > > Broadcast: 192.168.254.127 11000000.10101000.11111110.0 1111111 > > Hosts/Net: 126 Class C, Private Internet > > > > So all your machines would have the same network and broadcast, and you > > would make them all use your gateway box as the default route. > > > > As you can see, a 255.255.255.255 netmask (/32) is only one host: > > sysjo@hades:~$ ipcalc 192.168.254.34/32 > > Address: 192.168.254.34 11000000.10101000.11111110.00100010 > > Netmask: 255.255.255.255 = 32 11111111.11111111.11111111.11111111 > > Wildcard: 0.0.0.0 00000000.00000000.00000000.00000000 > > => > > Hostroute: 192.168.254.34 11000000.10101000.11111110.00100010 > > Hosts/Net: 1 Class C, Private Internet > > > > > > What you need to do is use IP calc to see what the network and broadcast > > are and set those, although on FreeBSD 4.X (I think anyway, someone > > correct me if I am wrong) you can just put in your /etc/rc.conf > > ifconfig_bge0="inet 192.168.254.32/25" > > or > > ifconfig_bge0="inet 192.168.254.32 netmask 255.255.255.128" > > > > And FreeBSD will work out the network and broadcast for you. > > > >> Today, I was in this exact position where I was tring to add an (the > >> first > >> one one THAT machine, from that block) IP from a block that is almost > >> completely used up on another server, and the one I was adding it to > >> would > >> not take it. When I tried adding it with a 255.255.255.255 netmask, and a > >> broadcast eaqual to the amount of IPs from that block - it worked. > > > > Like I said before, there is only 1 IP in a /32 block, and the broadcast > > will be either a.b.c.127 or a.b.c.255 depending whether you have the > > first or second subnet inside that class C. > > > > Hope this helps > > > > -John > > > > > > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >
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