How to determine an appropriate IP address based on the subnet mask.

Issue
Some devices require the use of a subnet mask. If not set properly the symptoms will be no communications between the device and software. All settings will look normal and all static address requirements will be filled.

Product Line
All Ethernet Devices

Environment
Network Communications


Cause
In a situation where a customer is attempting to directly connect to the meter for a pre-deployment configuration where it is necessary to assign a temporary static IP address to the customer's computer based off the subnet mask assigned to the meter. In most situations, customers will use a standard subnet mask of 255.255.255.0. This is a standard class C network also known as a /24 that allows the full use of all IP addressing in the host address's range.

A host IP address of 10.10.10.1 with a subnet mask of 255.255.255.0 would allow the host to communicate with any other IP address of 10.10.10.1-254. (1 is already used and 0, 255 is reserved)

This is simple and easy to calculate an IP address that the meter can use and still communicate with a server or the customer's computer.

Resolution
Step 1: Locate the netmask assigned to the meter you are wanting to communicate with. Note the / class number it is a member of.

/ Class	Addresses	Hosts	Netmask	Class C amount
30	4	2	255.255.255.252	1/64
29	8	6	255.255.255.248	1/32
28	16	14	255.255.255.240	1/16
27	32	30	255.255.255.224	1/8
26	64	62	255.255.255.192	1/4
25	128	126	255.255.255.128	1/2
24	256	254	255.255.255.0	1
23	512	510	255.255.254.0	2
22	1024	1022	255.255.252.0	4
21	2048	2046	255.255.248.0	8
20	4096	4094	255.255.240.0	16
19	8192	8190	255.255.224.0	32
18	16384	16382	255.255.192.0	64
17	32768	32766	255.255.128.0	128
16	65536	65534	255.255.0.0	256

Step 2: Locate the corresponding class block. Then decide which Address range your meter address falls into. Addresses in the address range are valid for that class network.

Example: If you have a /25 with an IP address of  10.10.10.200 your meter falls into the first chart  /25 and the second row labeled 129-254.  Therefore you should set the computer IP address to 10.10.10.129-254 (Excluding 200).

/25

Network Number	Address Range	Broadcast Address
0	1-126	127
128	129-254	255

/26

Network #	Address Range	Broadcast Address
0	1-62	63
64	65-126	127
128	129-190	191
192	193-254	255

/27

Network Number	Address Range	Broadcast Address
0	1-30	31
32	33-62	63
64	65-94	95
96	97-126	127
128	129-158	159
160	161-190	191
192	193-222	223
224	225-254	255

/28

Network Number	Address Range	Broadcast Address
0	1-14	15
16	17-30	31
32	33-46	47
48	49-62	63
64	65-78	79
80	81-94	95
96	97-110	111
112	113-126	127
128	129-142	143
144	145-158	159
160	161-174	175
176	177-190	191
192	193-206	207
208	209-222	223
224	225-238	239
240	241-254	255

/29

Network number	Address Range	Broadcast Address
0	1-6	7
8	9-14	15
16	17-22	23
24	25-30	31
32	33-38	39
40	41-46	47
48	49-54	55
56	57-62	63
64	65-70	71
72	73-78	79
80	81-86	87
88	89-94	95
96	97-102	103
104	105-110	111
112	113-118	119
120	121-126	127
128	129-134	135
136	137-142	143
144	145-150	151
152	153-158	159
160	161-166	167
168	169-174	175
176	177-182	183
184	185-190	191
192	193-198	199
200	201-206	207
208	209-214	215
216	217-222	223
224	225-230	231
232	233-238	239
240	241-246	247
248	249-254	255

/30

Network Number	Address Range	Broadcast Address
0	1-2	3
4	5-6	7
8	9-10	11
12	13-14	15

/30

0	1-2	3
4	5-6	7
8	9-10	11
12	13-14	15
16	17-18	19
20	21-22	23
24	25-26	27
28	29-30	31
32	33-34	35
36	37-38	39
40	41-42	43
44	45-46	47
48	49-50	51
52	53-54	55
56	57-58	59
60	61-62	63
64	65-66	67
68	69-70	71
72	73-74	75
76	77-78	79
80	81-82	83
84	85-86	87
88	89-90	91
92	93-94	95
96	97-98	99
100	101-102	103
104	105-106	107
108	109-110	111
112	113-114	115
116	117-118	119
120	121-122	123
124	125-126	127
128	129-130	131
132	133-134	135
136	137-138	139
140	141-142	143
144	145-146	147
148	149-150	151
152	153-154	155
156	157-158	159
160	161-162	163
164	165-166	167
168	169-170	171
172	173-174	175
176	177-178	179
180	181-182	183
184	185-186	187
188	189-190	191
192	193-194	195
196	197-198	199
200	201-202	203
204	205-206	207
208	209-210	211
212	213-214	215
216	217-218	219
220	221-222	223
224	225-226	227
228	229-230	231
232	233-234	235
236	237-238	239
240	241-242	243
244	245-246	247
248	249-250	251

252

253-254

255

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