To use Team O'clock behind a firewall you need to whitelist the service's IP addresses. However, Team O'clock is using  dynamic ip addresses, hosted in the us-east-1 AWS region. 


Although not recommended, you can still whitelist the entire AWS US East Region using the following IP prefixes from the AWS IP Ranges documentation:


15.230.56.104/31
52.93.127.163/32
3.2.0.0/24
15.230.137.0/24
52.4.0.0/14
50.16.0.0/15
52.95.208.0/22
52.93.127.169/32
52.94.244.0/22
64.252.69.0/24
15.230.56.130/31
52.93.50.128/32
52.93.50.140/31
52.95.41.0/24
176.32.125.244/31
3.4.0.0/24
52.93.91.102/32
13.34.29.224/27
13.248.124.0/24
18.232.0.0/14
150.222.2.0/24
52.93.50.136/31
52.93.50.166/31
54.156.0.0/14
54.236.0.0/15
99.150.8.0/21
15.230.130.0/24
52.93.50.146/31
52.93.50.156/31
52.93.127.124/32
52.144.193.128/26
107.20.0.0/14
15.230.40.0/24
52.93.50.174/31
15.230.56.90/31
52.93.51.28/32
52.93.91.101/32
15.230.66.0/26
52.46.252.0/22
52.93.50.142/31
150.222.227.0/24
13.34.29.128/27
52.119.206.0/23
176.32.125.230/31
52.93.127.218/32
205.251.244.0/23
52.93.50.178/31
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54.239.98.0/24
176.32.125.228/31
13.34.30.128/27
54.144.0.0/14
15.230.56.190/31
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75.101.128.0/17
176.32.125.234/31
52.144.192.0/26
13.34.30.160/27
67.202.0.0/18
54.226.0.0/15
162.250.237.0/24
15.230.56.94/31
64.187.128.0/20
99.82.188.0/22
15.230.18.0/24
52.93.127.201/32
150.222.79.0/24
3.224.0.0/12
15.230.56.92/31
52.93.50.162/31
52.93.50.184/31
52.144.192.192/26
54.221.0.0/16
54.240.202.0/24
15.230.56.134/31
52.95.63.0/24
52.93.126.215/32
52.93.127.217/32
68.66.112.0/20
54.239.112.0/24
34.192.0.0/12
52.95.216.0/22
52.119.232.0/21
54.231.244.0/22
150.222.99.0/24
150.222.218.0/24
176.32.125.250/31
52.93.127.167/32
54.239.108.0/22
64.252.68.0/24
52.93.50.148/31
52.94.68.0/24
99.77.191.0/24
15.230.56.102/31
15.230.56.152/31
44.192.0.0/11
15.230.56.156/31
52.93.50.129/32
54.239.8.0/21
207.171.176.0/20
162.250.238.0/23
150.222.100.0/24
15.230.56.168/31
52.93.50.130/32
13.34.30.96/27
52.93.127.219/32
13.34.29.96/27
52.93.127.18/32
176.32.125.252/31
15.230.56.140/31
205.251.246.0/24
15.230.56.120/31
23.20.0.0/14
52.46.168.0/23
52.93.91.115/32
64.252.64.0/24
3.4.1.0/24
72.21.192.0/19
15.230.56.124/31
15.230.56.172/31
54.231.0.0/17
52.93.126.123/32
52.94.124.0/22
52.93.50.176/31
54.240.216.0/22
99.82.166.0/24
52.93.91.96/32
52.93.91.105/32
52.44.0.0/15
13.34.30.64/27
15.230.56.184/31
52.93.91.111/32
52.93.123.255/32
15.230.56.106/31
15.230.56.186/31
205.251.247.0/24
15.193.6.0/24
52.93.127.182/32
52.90.0.0/15
52.93.91.114/32
13.34.30.0/27
52.0.0.0/15
15.230.56.170/31
52.54.0.0/15
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52.119.196.0/22
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150.222.71.0/24
52.93.50.190/31
13.34.29.160/27
15.230.56.86/31
99.77.129.0/24
99.82.171.0/24
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52.144.200.64/26
13.34.31.64/27
15.230.56.108/31
35.153.0.0/16
52.144.192.128/26
52.216.0.0/15
162.250.236.0/24
52.46.250.0/23
150.222.205.0/24
15.230.56.98/31
15.230.56.178/31
52.93.91.112/32
52.200.0.0/13
15.230.56.128/31
34.224.0.0/12
13.34.31.96/27
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52.93.127.221/32
52.144.195.0/26
52.93.50.164/31
52.93.64.0/24
13.34.29.64/27
15.230.56.154/31
50.19.0.0/16
150.222.73.0/24
15.221.4.0/23
15.230.56.110/31
52.93.127.172/32
3.2.3.0/24
15.230.38.0/24
15.230.56.76/31
52.93.127.68/32
174.129.0.0/16
52.95.255.80/28
150.222.87.0/24
15.230.65.192/26
18.208.0.0/13
52.95.245.0/24
99.77.187.0/24
176.32.125.254/31
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176.32.125.236/31
52.93.91.108/32
52.93.127.122/32
99.82.167.0/24
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184.72.128.0/17
205.251.248.0/24
15.230.56.182/31
15.230.56.66/31
15.230.56.126/31
54.80.0.0/13
15.230.142.0/24
52.20.0.0/14
52.94.201.0/26
15.230.56.150/31
54.242.0.0/15
216.182.238.0/23
99.83.101.0/24
150.222.224.0/24
13.34.31.32/27
52.94.192.0/22
15.230.56.78/31
52.95.52.0/22
52.93.254.0/24
99.82.175.0/24
99.83.88.0/21
52.119.214.0/23
208.86.88.0/23
15.230.56.142/31
54.208.0.0/15
99.83.64.0/21
15.221.24.0/21
150.222.237.0/24
15.230.56.100/31
52.93.127.180/32
15.230.56.64/31
15.230.56.84/31
52.93.50.144/31
52.94.224.0/20
99.77.128.0/24
15.230.56.82/31
150.222.226.0/24
54.152.0.0/16
176.32.125.240/31
54.240.208.0/22
52.70.0.0/15
52.94.248.0/28
52.119.212.0/23
52.93.50.168/31
52.93.127.19/32
52.93.127.216/32
99.77.254.0/24
13.248.103.0/24
15.230.56.176/31
176.32.125.232/31
3.5.0.0/18
15.177.64.0/23
52.86.0.0/15
52.93.91.113/32
52.93.97.0/24
15.230.56.252/31
52.93.127.162/32
205.251.224.0/22
15.230.56.112/31
54.172.0.0/15
52.93.127.200/32
18.204.0.0/14
52.93.91.110/32
54.88.0.0/14
99.78.192.0/22
52.95.62.0/24
15.230.56.136/31
52.93.50.134/31
52.93.127.183/32
3.2.2.0/24
52.93.50.131/32
64.252.66.0/24
150.222.110.0/24
3.3.5.0/24
52.2.0.0/15
52.93.127.125/32
176.32.96.0/21
184.72.64.0/18
13.248.108.0/24
52.95.108.0/23
52.144.193.0/26
52.93.123.136/32
52.95.48.0/22
54.240.232.0/22
150.222.143.0/24
52.119.224.0/21
216.182.232.0/22
15.230.56.138/31
15.230.56.118/31
150.222.223.0/24
15.230.65.128/26
15.230.145.0/24
52.93.50.138/31
52.93.50.152/31
199.127.232.0/22
99.82.176.0/21
204.236.192.0/18
35.168.0.0/13
72.44.32.0/19
52.93.51.29/32
52.93.1.0/24
52.93.50.160/31
52.93.50.132/31
150.222.236.0/24
3.4.2.0/24
13.34.31.0/27
52.46.170.0/23
54.92.128.0/17
54.239.0.0/28
99.77.151.0/24
216.182.224.0/21
52.93.91.98/32
54.204.0.0/15
15.230.56.148/31
54.196.0.0/15
176.32.125.226/31
52.94.252.0/23
15.230.35.0/24
52.93.249.0/24
207.171.160.0/20
15.230.56.166/31
13.34.30.32/27
15.230.56.132/31
52.72.0.0/15
52.93.126.212/32
176.32.125.192/27
176.32.125.238/31
15.230.56.146/31
54.160.0.0/13
15.230.56.254/31
52.93.127.164/32
54.234.0.0/15
52.92.16.0/20
172.96.97.0/24
52.93.126.122/32
52.94.254.0/23
52.93.127.185/32
15.230.56.164/31
3.208.0.0/12
15.221.0.0/24
15.230.56.70/31
52.93.91.103/32
176.32.124.128/25
184.73.0.0/16
54.174.0.0/15
52.93.4.0/24
52.93.59.0/24
54.224.0.0/15
99.82.165.0/24
52.93.50.194/31
3.80.0.0/12
15.230.56.68/31
15.230.56.174/31
52.93.50.154/31
52.93.126.213/32
52.144.200.128/26
54.240.196.0/24
150.222.66.0/24
52.93.127.165/32
13.34.29.192/27
176.32.125.246/31
15.230.56.116/31
150.222.222.0/24
52.93.127.181/32
52.93.126.214/32
52.93.127.173/32
64.252.67.0/24
54.198.0.0/16
13.34.30.192/27
15.230.56.250/31
52.46.128.0/19
52.93.127.166/32
176.32.125.242/31
15.230.56.88/31
52.93.91.109/32
52.93.127.123/32
52.93.50.186/31
52.144.193.64/26
54.239.16.0/20
13.34.30.224/27
15.230.56.180/31
52.144.194.0/26
52.46.164.0/23
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52.93.91.106/32
54.240.228.0/23
176.32.120.0/22
15.230.56.96/31
15.230.56.158/31
52.93.50.170/31
52.93.50.192/31
72.41.0.0/20
54.210.0.0/15
150.222.76.0/24
13.248.116.0/24
15.230.56.74/31
52.93.76.0/24
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52.93.127.184/32
100.24.0.0/13
15.230.56.248/31
150.222.136.0/24
52.93.127.220/32
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209.54.176.0/21
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150.222.138.0/24
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52.46.166.0/23
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107.23.255.0/26
54.243.31.192/26
54.231.0.0/17
52.216.0.0/15
3.5.0.0/18
52.92.16.0/20
3.218.180.0/22
52.119.232.0/21
52.119.224.0/21
52.94.0.0/22
3.2.0.0/24
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50.16.0.0/15
64.252.69.0/24
3.4.0.0/24
18.232.0.0/14
54.156.0.0/14
54.236.0.0/15
99.150.8.0/21
107.20.0.0/14
54.144.0.0/14
75.101.128.0/17
67.202.0.0/18
54.226.0.0/15
162.250.237.0/24
64.187.128.0/20
3.224.0.0/12
54.221.0.0/16
68.66.112.0/20
34.192.0.0/12
64.252.68.0/24
99.77.191.0/24
44.192.0.0/11
162.250.238.0/23
23.20.0.0/14
64.252.64.0/24
3.4.1.0/24
52.44.0.0/15
15.193.6.0/24
52.90.0.0/15
52.0.0.0/15
52.54.0.0/15
99.77.129.0/24
35.153.0.0/16
162.250.236.0/24
52.200.0.0/13
34.224.0.0/12
50.19.0.0/16
3.2.3.0/24
174.129.0.0/16
52.95.255.80/28
18.208.0.0/13
52.95.245.0/24
99.77.187.0/24
184.72.128.0/17
54.80.0.0/13
52.20.0.0/14
52.94.201.0/26
54.242.0.0/15
216.182.238.0/23
208.86.88.0/23
54.208.0.0/15
99.77.128.0/24
54.152.0.0/16
52.70.0.0/15
52.94.248.0/28
99.77.254.0/24
3.5.0.0/18
15.177.64.0/23
52.86.0.0/15
54.172.0.0/15
18.204.0.0/14
54.88.0.0/14
3.2.2.0/24
64.252.66.0/24
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52.2.0.0/15
184.72.64.0/18
216.182.232.0/22
204.236.192.0/18
35.168.0.0/13
72.44.32.0/19
3.4.2.0/24
54.92.128.0/17
99.77.151.0/24
216.182.224.0/21
54.204.0.0/15
54.196.0.0/15
52.72.0.0/15
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3.208.0.0/12
184.73.0.0/16
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3.80.0.0/12
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