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Every 2nd hour all workstations lose internet connection for 10 seconds. The ISP tech support seems to be reluctant to resolve the issue so I am trying to fix it myself. Here is a diagram of our network:

Network Diagram

I wrote a shell script to log the dropouts. The script (on a remote server) pings our external IP address every second and logs the periods where pings fail. Here is an excerpt from the log:

=======================================
Failure Start           Length
=======================================
2016-08-16 17:52:11     10 sec
2016-08-16 19:52:23     10 sec
2016-08-16 21:52:34     10 sec
2016-08-17 23:52:46     10 sec

Also, here is an excerpt from the router log:

50 2016-08-16 17:29:03 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
51 2016-08-16 17:31:07 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
52 2016-08-16 17:33:11 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
53 2016-08-16 17:35:15 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
54 2016-08-16 17:36:51 <5> : WAN1:DHCP lease timeout, beging a new one. 
55 2016-08-16 17:38:51 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
56 2016-08-16 17:40:55 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
57 2016-08-16 17:42:59 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
58 2016-08-16 17:45:03 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
59 2016-08-16 17:47:07 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
60 2016-08-16 17:49:11 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
61 2016-08-16 17:51:15 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
62 2016-08-16 17:51:51 <5> : WAN1:DHCP renew fail, begin a new discovery. 
63 2016-08-16 17:52:02 <5> : WAN1:DHCP getting IP succeeded, and IP addr:XX.XX.XX.97, mask:255.255.254.0, gateway:XX.XX.XX.1.
64 2016-08-16 18:54:06 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
65 2016-08-16 18:56:10 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
66 2016-08-16 18:58:14 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
67 2016-08-16 19:00:18 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
68 2016-08-16 19:02:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
69 2016-08-16 19:04:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
70 2016-08-16 19:06:30 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
71 2016-08-16 19:08:34 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
72 2016-08-16 19:10:38 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
73 2016-08-16 19:12:42 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
74 2016-08-16 19:14:46 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
75 2016-08-16 19:16:50 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
76 2016-08-16 19:18:54 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
77 2016-08-16 19:20:58 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
78 2016-08-16 19:23:02 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
79 2016-08-16 19:25:06 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
80 2016-08-16 19:27:10 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
81 2016-08-16 19:29:14 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
82 2016-08-16 19:31:18 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
83 2016-08-16 19:33:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
84 2016-08-16 19:35:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
85 2016-08-16 19:37:02 <5> : WAN1:DHCP lease timeout, beging a new one. 
86 2016-08-16 19:39:02 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
87 2016-08-16 19:41:07 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
88 2016-08-16 19:43:10 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
89 2016-08-16 19:45:14 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
90 2016-08-16 19:47:19 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
91 2016-08-16 19:49:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
92 2016-08-16 19:51:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
93 2016-08-16 19:52:02 <5> : WAN1:DHCP renew fail, begin a new discovery. 
94 2016-08-16 19:52:14 <5> : WAN1:DHCP getting IP succeeded, and IP addr:XX.XX.XX.97, mask:255.255.254.0, gateway:XX.XX.XX.1.
95 2016-08-16 20:54:18 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
96 2016-08-16 20:56:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
97 2016-08-16 20:58:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
98 2016-08-16 21:00:30 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
99 2016-08-16 21:02:33 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
100 2016-08-16 21:04:37 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
101 2016-08-16 21:06:41 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
102 2016-08-16 21:08:46 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
103 2016-08-16 21:10:50 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
104 2016-08-16 21:12:54 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
105 2016-08-16 21:14:58 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
106 2016-08-16 21:17:02 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
107 2016-08-16 21:19:06 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
108 2016-08-16 21:21:09 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
109 2016-08-16 21:23:14 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
110 2016-08-16 21:25:17 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
111 2016-08-16 21:27:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
112 2016-08-16 21:29:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
113 2016-08-16 21:31:30 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
114 2016-08-16 21:33:34 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
115 2016-08-16 21:35:38 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
116 2016-08-16 21:37:14 <5> : WAN1:DHCP lease timeout, beging a new one. 
117 2016-08-16 21:39:14 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
118 2016-08-16 21:41:18 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
119 2016-08-16 21:43:22 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
120 2016-08-16 21:45:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
121 2016-08-16 21:47:30 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
122 2016-08-16 21:49:34 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
123 2016-08-16 21:51:38 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
124 2016-08-16 21:52:14 <5> : WAN1:DHCP renew fail, begin a new discovery. 
125 2016-08-16 21:52:25 <5> : WAN1:DHCP getting IP succeeded, and IP addr:XX.XX.XX.97, mask:255.255.254.0, gateway:XX.XX.XX.1.
126 2016-08-16 22:54:29 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
127 2016-08-16 22:56:33 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
128 2016-08-16 22:58:37 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
129 2016-08-16 23:00:41 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
130 2016-08-16 23:02:45 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
131 2016-08-16 23:04:49 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
132 2016-08-16 23:06:54 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
133 2016-08-16 23:08:58 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
134 2016-08-16 23:11:02 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
135 2016-08-16 23:13:05 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
136 2016-08-16 23:15:09 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
137 2016-08-16 23:17:13 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
138 2016-08-16 23:19:17 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
139 2016-08-16 23:21:21 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
140 2016-08-16 23:23:26 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
141 2016-08-16 23:25:30 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
142 2016-08-16 23:27:34 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
143 2016-08-16 23:29:38 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
144 2016-08-16 23:31:42 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
145 2016-08-16 23:33:46 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
146 2016-08-16 23:35:50 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
147 2016-08-16 23:37:25 <5> : WAN1:DHCP lease timeout, beging a new one. 
148 2016-08-16 23:39:25 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
149 2016-08-16 23:41:29 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
150 2016-08-16 23:43:33 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
151 2016-08-16 23:45:37 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
152 2016-08-16 23:47:41 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
153 2016-08-16 23:49:45 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
154 2016-08-16 23:51:49 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
155 2016-08-16 23:52:25 <5> : WAN1:DHCP renew fail, begin a new discovery. 
156 2016-08-16 23:52:37 <5> : WAN1:DHCP getting IP succeeded, and IP addr:XX.XX.XX.97, mask:255.255.254.0, gateway:XX.XX.XX.1.
157 2016-08-17 00:54:42 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 
158 2016-08-17 00:56:46 <5> : WAN1:DHCP send DHCP-REQUEST timeout. 

Each time we get a dropout the router logs "DHCP renew fail" and "DHCP getting IP succeeded". What could be the issue? Does it have to do with lease time of the external IP address?

Also what are all these "DHCP send DHCP-REQUEST timeout" logs?

Thanks!

1 Answer 1

4

Looks like your ISP network admin has a broken config on DHCP. Standard setup for DHCP client is to call in when lease is half over to renew, and to keep trying until renewal takes place. The log tells me that your ISP has a 2 hour lease. But the halfway renewal is failing. Possibly blocked.

I also see that DHCP discovery is working, DHCP renew is not.

Keep after them. I suspect they have an opening for network administrator and someone else is trying to fill the role. Or they have a new one who is inexperienced. Read up on the DHCP RFC, and get on the phone with their support tech.

2
  • I think it's It's 50% and then 85% tcpipguide.com/free/…
    – user9517
    Aug 17, 2016 at 17:49
  • ietf.org/rfc/rfc2131.txt. T1 defaults to 1/2 lease. T2 defaults to 7/8 lease. The behavior in the log shows that the client is not getting DHCPACK and is returning to INIT state, at which time it is forced to stop all network activity (thus the described loss of connection for 10 seconds).
    – Jeter-work
    Aug 17, 2016 at 18:09

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