Virtual Router to Support Multicast

##### ISSUE TYPE

* Improvement Request

##### COMPONENT NAME

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Virtual Router
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##### CLOUDSTACK VERSION

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4.19.1.1
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##### CONFIGURATION

##### OS / ENVIRONMENT

##### SUMMARY

Currently Cloudstack Virtual Router doesnt support Multicast from external networks (eg. Private Gateway).

In our case, our customers require multicast support because they decode Stock Market Feeds from the Stock Exchange. And Majority Stock Exchange distributes market feeds in ITCH format, which is Multicast.

In order to overcome this limitation now, we had to resort to VNF + L2 Networks.

I also have a curious question, if Cloudstack VR does not support multicast, then why is there a UDP Protocol option in the Network ACL Rules?

##### STEPS TO REPRODUCE

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##### EXPECTED RESULTS

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For VR to support multicast natively
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##### ACTUAL RESULTS

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VR does not support multicast at the moment.
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該 issue 指出了 CloudStack 的 Virtual Router，並要求為外部網路提供原生多播支援，但沒有指定任何檔案、測試、命令或進入點。首先定位 Virtual Router 的網路實作，以及現有的協定或路由測試。對於所描述的外部網路使用案例，當多播流量能夠透過 Virtual Router 原生運作時，即表示完成。

由索引模型根據 Issue 內容生成。