Little Network with Two USG

Alby_Mat Posts: 1
edited March 2023 in Security

Hello Community,

I have a little trouble that drived me crazy since some days.

I have a test enviroment, that i want to replicate in a customer enviroment in the future.

I have:

1 Zyxel USG FLEX100

1 Zyxel USG 20 (I know that it is so old and obsolete but i use only for lab enviroment)

1 Switch Brocade, use for test enviroment.

My test lab is to create a VLan (Called Vlan33),use the default LAN 192.168.1.x,and configure everything so that can reach every device in the LAN and VLAN33, and LAN and VLAN33 can communicate.

So, my enviroment is:

The Zyxel USG FLEX 100 have an IP Address on LAN1 and it is the Gateway for VLAN33 (IP Also it is the DHCP Server for VLAN33

The Zyxel USG 20 have IP Address on LAN1 and have a IP on VLAN33 (, the Gateway is the USG FLEX 100

The Switch brocade, have an IP Address, work perfectly, and the port is correctly TAGGED/UNTAGGED on VLAN/LAN and rightly.

I have connect, the two firewall to the switch Brocade, and i have connect my pc to one port of the switch, Untagged on VLAN33. I can take an IP on VLAN33 ( in this case) and everything works fine.

In Each firewall i have check the checkbox "ENable Policy Control) (in the USG 20, that is old, hav eonly the VOice Firewall)

I leaved the default Policy Control Rule (LAN1_to_Outgoing) and add VLAN33_to_Outgoing in both firewall

So, the problem is:

When i connect to the VLAN33 through the switch, i can ping the three devices correctly (, i can reach the webpage of and BUT i cannot reach the WebPage of

This is the ping:

And, this is the netstat -an when i try to connect in the Webpage of

BUT after few try, IF i disable the Policy Control of (USG FLEX100) and leaving enable (or disabled is the same) the Policy COntrol of (USG 20), i CAN reach the WebPage. If i enabled again the Policy Control of USG FLEX100 i cannot reach again the webpage of….

Guys, what i missing??

EDIT: This is a LOG from when i try to reach

All Replies

  • zyman2008
    zyman2008 Posts: 199  Master Member
    First Anniversary 10 Comments Friend Collector First Answer

    Usually a triangle route issue if multiple Stateful firewall as router in the same subnet.

    Enable “Allow Asymmetrical Route” option in policy control page. On both USG20 and USG FLEX firewall.

  • Zyxel_Jeff
    Zyxel_Jeff Posts: 1,066  Zyxel Employee
    First Anniversary 10 Comments Friend Collector First Answer

    Hi @Alby_Mat

    It should be a triangle route problem, you can enable “Allow Asymmetrical Route” option on USG Flex100 and USG20 to avoid this problem. Thanks.

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