Troubleshooting a campus wireless network

" Problem Description ": A university wireless network launched two signals, one for teacher, the other for student, the pre-deployment phase of all normal, after the students back to school, began to have some students to reflect the connection student signal can not access the Internet, the specific performance of, The wireless signal can be connected, but the wireless terminals (including mobile phones and notebooks) get no address, assigning 169.254.175.149 directly, while connecting teacher signals is normal.
" Troubleshooting ":

1, the synthesis of these days of failure to declare the time of observation, there is no fixed time period, basically the whole day will have a chance of failure phenomenon;
2, to troubleshoot the teacher and student the two signals of the policy settings, and so on, basically the same;
3, just started to suspect that the DHCP address pool is not enough, but for student, we allocated 4 22-bit address pool, available address about 4088, that is, 4088 devices can be online at the same time, but in the event of recurrence, the total online device is 1915, under normal circumstances, the address pool will not be exhausted.
4, in the event of failure, the capture packet observation, and under normal circumstances also carried out to observe the comparison.
【Normal situation】：
1, the PC first send a broadcast packet, asked to assign the address of the person where? (DHCP Discover discovers where the DHCP server is);
2, the DHCP received the PC broadcast packet, will respond to a, said I am here, my home address is xxxx. (The DHCP offer message will contain the IP address of the DHCP server);
3. After receiving the DHCP offer message, the PC will send a request packet to the DHCP server IP provided in this message, saying "I am a student who is just reporting, please give me a student ID, assign a school number to me." (DHCP request, requesting the server to assign an IP address);
4, the DHCP server receives the request, will give the "student" assigned a "school number", will send a message to him said "This is your study number and validity period, you put the study number into your student card." (DHCP ACK will have assigned IP address information, DNS information, lease information, etc.);
5, the PC receives the assigned number and the lease period, it will automatically bind the information with the network card used, you can start the normal communication.
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Figure one IP request process
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Figure 2 DHCP Discover Package
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Figure 3 DHCP offer
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Figure 4 DHCP Request
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Figure 5 DHCP ACK

While we are in the process of recurrence, grasping the package to see that this is not normal, it is the problem of the DHCP server, in order to further confirm, we also call up the address allocation records to view.
Pick up

" Troubleshooting "
5, view the address assignment record, through the sorting to see the discovery rule: each paragraph address is from 10. X.x.3 started, and ended with 10.x.x.254, and did not continue to assign IP addresses, equivalent to the DHCP server only to student this signal to the user assigned a 4 segment 24-bit address, than originally envisaged allocation of less than 75% of the address. Therefore, the reason for this fault is that the address pool is full;
6. Check the DHCP server settings again, and find that the start address is set to 10 on a policy setting. X.x.3, to 10. The end of the x.x.254, equivalent to the address pool is allocated 4 22-bit address pool, but the policy is limited to 4 segment 24-bit address, the end address of this policy is modified to the correct end address, the symptom disappears.

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Ps:
1, in the implementation phase, each step of the setup must be carefully examined;
2, some problems only when the user is large enough to find, even if the pre-test to be careful, the test of the user base does not go, some problems will not be exposed, the implementation of the project, it is best to have one months on-line test time (public test), which is why many large-scale games, The site before the normal use of a "public test", no problem, and then fully online reasons.

I am it small white, if there are errors, welcome point!

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Troubleshooting a campus wireless network