Bridge one of WAN IPs to Cisco

Hello Lubor Kacian,

Thank you for reaching out to the community, I may not have understood fully your requirement properly but if I anticipate it correctly, then I would suggest you to refer the following KBAs below:
1.)  Send web requests through an upstream proxy in LAN - https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Routing/UpstreamProxy/RoutingConnectParentProxyLAN/index.html
2.) Send web requests through an upstream proxy in WAN - https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Routing/UpstreamProxy/RoutingConnectUpstreamProxyWAN/index.html

Hi Lubor Kacian,

ether you bridge your WAN interface with another port on your Sophos or you put a simple switch between your ISP modem and Sophos, where you connect your Sophos (WAN port) and the Cisco (WAN port) to it.

Updated my post with a simple diagram

But WAN IP has /28 mask and I need forward one IP from this WAN subnet from Sophos to Cisco directly using some other ether Port on Sophos.

It is possible ?

You just have to add the desired IP as fixed on your Cisco device and thats all (with your /28 subnet mask)

This is what I need . Cisco must have this one of WAN IP.

This is what I need

Yeah - you can bridge Port2 and Port3 together and the Cisco device needs as fixed ip a.b.c.211/28

it is possible with the Sophos XG firewall, please see this KB below this should help. You do not need to bridge anything here 

https://support.sophos.com/support/s/article/KB-000035927?language=en_US

Thomas, have you tested this? I'm trying to set up two ports as part of a WAN bridge, and unable to add two unconfigured interfaces to the bridge. I get the error "You can set only one zone as a WAN"