# \[20190128190529\] Additional Rack Parameters **URL:** \ **Category:** Releases\ **Created:** [January 30, 2019, 3:36am UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36 "2019-01-30T03:36:17Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![ddollar](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/ddollar/32/3_2.png) [@ddollar](https://community.convox.com/u/ddollar)\ **Post date:** [January 30, 2019, 3:36am UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/1 "2019-01-30T03:36:17Z")
This release adds new new Rack parameters: `AvailabilityZones` allows you to specify which AZs your Rack will use. Please note that changing these on an already-installed Rack will require updating your Subnet CIDRs at the same time since two subnets can not exist with the same CIDR simultaneously. `InstancePolicy` is the ARN of a custom IAM policy to add to the instance roles. This can be helpful if you need to install additional agents, et al at the instance level. - [#3094](https://github.com/convox/rack/pull/3094) allow specifying azs [[@ddollar](https://github.com/ddollar)] - [#3097](https://github.com/convox/rack/pull/3097) allow adding additional instance policy [[@ddollar](https://github.com/ddollar)] - [#3099](https://github.com/convox/rack/pull/3099) handle --options to ADD/COPY [[@ddollar](https://github.com/ddollar)] - [#3102](https://github.com/convox/rack/pull/3102) allow AvailabilityZones to be overridden with params set [[@ddollar](https://github.com/ddollar)] ---
**Author:** ![jay.janssen](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/jay.janssen/32/17_2.png) [@jay.janssen](https://community.convox.com/u/jay.janssen)\ **Post date:** [January 30, 2019, 12:28pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/2 "2019-01-30T12:28:49Z")
@ddollar I’m interested in using the AvailabilityZones feature, but I’m unclear what is needed around “updating your Subnet CIDRs”. Can you give some extra detail? ---
**Author:** ![ddollar](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/ddollar/32/3_2.png) [@ddollar](https://community.convox.com/u/ddollar)\ **Post date:** [January 30, 2019, 12:42pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/3 "2019-01-30T12:42:24Z")
Two subnets can not exist on the same VPC with the same CIDR. Because CloudFormation creates new resources then deletes old ones, if you change `AvailabilityZones` you will need to choose a new CIDR for that AZ for the update. For example, if you update the third AZ in your `AvailabilityZones` parameter you will need to choose new, non-conflicting value(s) for `Subnet2CIDR` (and `SubnetPrivate2CIDR` if you are in `Private=Yes` mode) Once the update completes, you will need to re-deploy any Generation 1 applications on your Rack. Please be very careful with this update because if it rolls back it can leave your app in a broken state (the old subnets will not be there for it to roll back to) ---
**Author:** ![jay.janssen](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/jay.janssen/32/17_2.png) [@jay.janssen](https://community.convox.com/u/jay.janssen)\ **Post date:** [January 30, 2019, 1:51pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/4 "2019-01-30T13:51:38Z")
So if I understand correctly, if I want to swap out a specific AZ, I need to know the CIDR that subnet is using currently. ``` AvailabilityZones us-east-1c,us-east-1e,us-east-1a Private No Subnet0CIDR 10.0.1.0/24 Subnet1CIDR 10.0.2.0/24 Subnet2CIDR 10.0.3.0/24 ``` In my case I want to get rid of us-east-1e, because it doesn’t support t3. Looking at my ECS cluster in the AWS Console, I can tell that 3 of my nodes are in 1e and three of them also happen to be on the 10.0.2 subnet, so Subnet1CIDR. Does the AZ order match the Subnet0-2 order? So, I think then my command would be: `convox rack params set AvailablityZones=us-east-1c,us-east-1b,us-east-1a Subnet1CIDR=10.0.4.0/24` Is that right? ---
**Author:** ![ddollar](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/ddollar/32/3_2.png) [@ddollar](https://community.convox.com/u/ddollar)\ **Post date:** [January 30, 2019, 1:59pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/5 "2019-01-30T13:59:45Z")
Yes, that’s all right, unless your Rack is in Private mode in which case that `10.0.4.0/24` would conflict with one of the private subnets. ---
**Author:** ![jay.janssen](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/jay.janssen/32/17_2.png) [@jay.janssen](https://community.convox.com/u/jay.janssen)\ **Post date:** [January 30, 2019, 2:00pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/6 "2019-01-30T14:00:47Z")
Ok, thanks. Currently I’m trying to figure out if t3 and us-east-1e are still incompatible… This might be a moot point for me. ---
**Author:** ![eravelo](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.convox.com/eravelo/32/22_2.png) [@eravelo](https://community.convox.com/u/eravelo)\ **Post date:** [January 30, 2019, 3:54pm UTC](https://community.convox.com/t/20190128190529-additional-rack-parameters/36/7 "2019-01-30T15:54:41Z")
Hi, Is this release ready for production? I just created a rack, and this version was picked-up. Thanks.