# Bad\_GatewayCommOff

**URL:** <https://forum.inductiveautomation.com/t/bad-gatewaycommoff/24156>\
**Category:** Module Development\
**Created:** [April 15, 2019, 4:03pm UTC](https://forum.inductiveautomation.com/t/bad-gatewaycommoff/24156 "2019-04-15T16:03:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![THK](https://avatars.discourse-cdn.com/v4/letter/t/71e660/32.png) [@THK](https://forum.inductiveautomation.com/u/THK)\
**Post date:** [April 15, 2019, 4:03pm UTC](https://forum.inductiveautomation.com/t/bad-gatewaycommoff/24156/1 "2019-04-15T16:03:06Z")

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When using preview mode in Designer I am getting Bad\_GatewayCommOff errors when writing values. Writing values works fine when in design mode using the tag browser window but when preview is turned on I get the error.

I am using Ignition 8.

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<div class="post-metadata">

**Author:** ![THK](https://avatars.discourse-cdn.com/v4/letter/t/71e660/32.png) [@THK](https://forum.inductiveautomation.com/u/THK)\
**Post date:** [April 19, 2019, 2:41pm UTC](https://forum.inductiveautomation.com/t/bad-gatewaycommoff/24156/2 "2019-04-19T14:41:29Z")

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Is there a parameter I need to enable to be able to write in preview mode?

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**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [April 19, 2019, 3:02pm UTC](https://forum.inductiveautomation.com/t/bad-gatewaycommoff/24156/3 "2019-04-19T15:02:56Z")

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You need to set the designer’s “Gateway Comm Mode”. Go to Project in the menu bar, then select ‘Comm Read/Write’. By default, a designer session will be in read-only mode.