determine IP for device

Question

I am configuring an eth1 interface on in Red Hat, but I don't understand exactly what the IP address should be.

I'm given an IP of 10.237.128.0/25. This means that the NETMASK would be 255.255.255.128; I understand this portion.

What I don't understand, is if eth1 is in fact a host device, what would the IPADDR address be?

Here are my guesses:

10.237.128.0/25
10.237.128.0 (since the NETMASK variable will be declared, thus making /25 unnecessary)
10.237.128.1-126 (If eth1 is considered a host, 8 0-bits and 8 1-bits would be unavailable on the network as a host, and the 128 bit is the network.)

That can't be your IP address, as it's a network. – Michael Hampton Mar 25 '13 at 21:16 — Michael Hampton, Mar 25 '13 at 21:16
A /25 is 128 IP addresses... – ceejayoz Mar 25 '13 at 21:17 — ceejayoz, Mar 25 '13 at 21:17
http://jodies.de/ipcalc?host=10.237.128.0&mask1=25&mask2= – user9517 Mar 25 '13 at 21:18 — user9517, Mar 25 '13 at 21:18

score 4 · Answer 1 · edited Apr 08 '18 at 16:29

The last one (something in range of 10.237.128.1-126)

If a network has the address 10.237.128.0/25, the number 25 refers to how many bits are contained in the network. From this, the number of bits left for address space can be calculated. As all IPv4 networks have 32 bits, and each “section” of the address denoted by the decimal points contains eight bits, “192.0.2.0/24” leaves seven bits to contain host addresses:

Netmask:   255.255.255.128 = 25  11111111.11111111.11111111.1 0000000

This is enough space for 126 host addresses. These host addresses are the IP addresses that are necessary to connect your machine to the Internet.

This is an adapted excerpt from this article: Understanding IP Addressing and CIDR Charts | RIPE Network Coordination Centre

score 4 · Accepted Answer · answered Mar 25 '13 at 21:20

4

Your IP address can be anything from 10.237.128.1 to 10.237.128.126

Address:   10.237.128.0          00001010.11101101.10000000.0 0000000
Netmask:   255.255.255.128 = 25  11111111.11111111.11111111.1 0000000

Network:   10.237.128.0/25       00001010.11101101.10000000.0 0000000 
Broadcast: 10.237.128.127        00001010.11101101.10000000.0 1111111
HostMin:   10.237.128.1          00001010.11101101.10000000.0 0000001
HostMax:   10.237.128.126        00001010.11101101.10000000.0 1111110
Hosts/Net: 126                   (Private Internet)

answered Mar 25 '13 at 21:20

user9517

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So would IPADDR be the equivalent of Address, or your former statement? – alrightgame Mar 25 '13 at 21:26
@alrightgame: yes – user9517 Mar 25 '13 at 21:29
Yes to which one? – alrightgame Mar 25 '13 at 21:32
It should be one of the addresses from HostMin to HostMax that isn't already taken. (So if someone gave you a gateway address, don't use that.) – JelmerS Mar 25 '13 at 21:38
@alrightgame: Anything between .1 and .126 – user9517 Mar 25 '13 at 21:39

determine IP for device

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