# Linux trasparent proxy - Iptable rules

**URL:** https://discourse.mitmproxy.org/t/linux-trasparent-proxy-iptable-rules/737
**Category:** help
**Created:** [November 28, 2017, 1:55pm UTC](https://discourse.mitmproxy.org/t/linux-trasparent-proxy-iptable-rules/737 "2017-11-28T13:55:34Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Karu](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mitmproxy.org/karu/32/234_2.png) [@Karu](https://discourse.mitmproxy.org/u/Karu)
#### Post date: [November 28, 2017, 1:55pm UTC](https://discourse.mitmproxy.org/t/linux-trasparent-proxy-iptable-rules/737/1 "2017-11-28T13:55:34Z")

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In [this tutorial](http://docs.mitmproxy.org/en/stable/transparent/linux.html):  
sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080  
sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 8080

How can I find port number in my system to replace those and what are the factors that decides the port numbers used in those iptable rules?

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### Author: ![Gigiarum](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mitmproxy.org/gigiarum/32/278_2.png) [@Gigiarum](https://discourse.mitmproxy.org/u/Gigiarum)
#### Post date: [November 29, 2017, 11:46am UTC](https://discourse.mitmproxy.org/t/linux-trasparent-proxy-iptable-rules/737/2 "2017-11-29T11:46:36Z")

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80 and 443 are the standard ports used in the browsers for almost all sites.  
8080 is the default mitmproxy port, you can configure it passing -p argument.