All Web pages loads very slowly with a fast internet connection

Question

Dear Sophos Team, 
 
 Our company moved to the latest Sophos XG 105 (firmware SFOS 17.1.0 GA) with 15 users and we are overall very happy with it. 
 We currently only have the base firewall licence and shortly the network & web protection (license not received yet). 
 
 We have it coupled with a modem ZYXEL that acts as a PPPoE with a Fiber Optical line at 100mb/s up and down. 
 
 When we test the connection speed with speedtest.net, everything goes fast at 99 mb/s which is perfect. 
 However, when we are surfing, the speed to access a page is extremely slow like if the Sophos was doing many checks before grading the different elements. 
 Before the change to Sophos with exactly the same line, we didn't have such a slow down which makes us beleive that it is coming from the Sophos. 
 We have added a Firewall rule Lan-to-Internet which is very basic without any scanning or protection. Only Maskerading is ticked -> Without this, no internet access. 
 Can someone kindly help us to reslove this issue please ? I have attached different screenshot below. 
 
 THANKS in advance 
 Sam

Samuel Venker · Answer

Hi Aditya, VikenNajarian, 
 IT WORKS !!!!!!!!!!!!! 
 
 The error was that the DNS was on "Static DNS" with 192.168.1.1 only. 
 I changed to "Obtain DNS from PPPoE" and rebooted the machine. 
 
 Now all is fast and furious ! I also put back the MSS back to automatic which is 1452. 
 Thanks for all your support ! 
 Sam

Aditya Patel · Answer

Hi Samuel Venker, 
 You could start by checking the interface negotiation 100FD or 100HD ,you may also check if there is any negotiation issue between WAN or LAN with the next in-line device. 
 Open Console go to Option 4 and typ ethe command 
 console > system dia uti band "press 'u' twice" 
 Check if there is any error's E/S (error/second) 
 If so then lower the link speed. 
 Also another step provide us the output of the command; 
 Console> sh net interfaces 
 You may obfuscate your Public Address for privacy and try to change the MSS value to 1452 and MTU to 1492.

Aditya Patel · Answer

Hi Samual , 
 You can set the MTU the same and check if the connection speed would improve using MSS value is 1412.

Aditya Patel · Answer

Hi SAM , 
 
 Best thing to check is by using a test website which has a low foot print, eg test website 103.23.140.55 
 
 on the Console of the XG firewall check the packet flow using command console> tcpdump'host 103.23.140.55 
 
 You could also try on bbc.com and share us the results . You may obscure the public address for privacy concern. 
 
 Also Check if the setting would help MTU 1492 and MSS 1412 or 1380

Deo Angelo Lim · Answer

Hi, 
 
 Good day! 
 
 Its either DNS settings or you may check you CPU usage / Memory Usage of the device on Diagnostic > System Graphs. 
 Warm Regards, 
 Deo