I got connected to Telstra Broadband Cable using smart-modem thing. Everything worked fine except my VPN to my office. My office VPN was connecting however, I was not able to connect to any office website or system.
To eliminate any possible issues on my end, tried 2 other internet providers as well as my Mobile data (optus) and everything worked OK. So that confirmed that the issue is with Telstra connection.
While googling, it seems that I was not the only one. Found a similar post here https://crowdsupport.telstra.com.au/t5/Home-Broadband/VPN-not-working-on-Big-Pond-Cable/td-p/543324 and tried changing my DNS as suggested in this post after which VPN office connectivity worked fine.
However, I tried to find the root cause so i rollback the DNS settings to the original which was just 192.168.0.1. While going through all the settings in modem, found out that the Firewall was enabled and set to medium (or default). Setting the firewall mode to "low" fixed the VPN connectivity.
To do this, you need to login to your smart-modem (192.168.0.1), go in Advanced mode and change the Firewall settings to "low".
Just posting this so if anyone else facing the same issue, know how to fix it.
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