Installation of Openwrt in router HG556a

Objective: Install Openwrt Chaos Calmer 15.05 on Huawei Hg556a router.
Firmware: OpenWRT 15.05 Chaos Calmer downloaded from https://wiki.openwrt.org/toh/huawei/hg556a 
Difficulty: Easy. 
We need: Router HG556a 
Software needed: OpenWrt 15.05 Chaos Calmer. 
More information: Openwrt HG556A

Step 1 - Identify router model and download firmware.

From this router we can find three different versions. Although externally they are equal, internally there are changes that lead us to the need to identify the version before installing it. We must fix on the serial numbers of the router and download the one that corresponds with our router:

SN (Serial number begins with ...)	Router version	Discharge
30462, 30562, 30605, 30608, 30634,30692	TO	Firmware A
30693, 31110, 31300	B	Firmware B
30555, 30694, 30695, 31301, 31507, 31525, 31901, 31902, 31935, 32505, 32557	C	Firmware C

Step 2 - Install firmware.

We connect a network cable from our computer to the router.

1. We give our team the IP address 192.168.1.2 or any other within the 192.168.1.0 range.
2. With the router turned off, press the RESTART button.
3. Turn on the router by pressing and holding the RESTART button for 15 seconds.
4. Then we access the web page http://192.168.1.1
5. In that page that appears we give to examine and select the file that we download .
6. Once selected, click on Update Software.
7. IT IS IMPORTANT THAT WE DO NOT INTERRUPT THIS PROCESS . The router will update and restart only.