anchor.diff:      - cf-router-network-properties
     ```
     
  -* When you create the instance groups for the routers, you must bind them to the correct AZ and to the correct network.
  +<% else %>
  +<%= vars.config_networking_is %>
  +<% end %>
  +
  +## <a id='config-dns-lb'></a>Step 5: Configure DNS and Load Balancers
  +
  +Create a separate domain name for each router instance group, and configure DNS to resolve these domain names to a load balancer that routes requests to the matching routers. 
  +
  +<p class="note"><strong>Note</strong>: You must configure your load balancers to forward requests for a given domain to one router instance group only.</p>
  +
  +As router instance groups may be responsible for separate isolation segments, and an application may be deployed to only one isolation segment, requests should only reach a router that has access to the applications for that domain name. Load balancing requests for a domain across more than router instance group can result in request failures unless all the router instance groups have access to the isolation segments where applications for that domain are deployed. 
  +
  +The sections below describe a configuration that routes applications from [distinct domain names](#distinct-domain), and a configuration that routes applications from a [shared domain name](#sharing-domain). The diagrams illustrate a topology with separate load balancers, but you could also use one load balancer with multiple interfaces.
  +
  +### <a id='distinct-domain'></a>Distinct Domain Names
  +
  +In a configuration that routes applications from distinct domain names:
  +
  +* Requests for system domain `*.cf-system.com` and the shared domain `*.cf-apps.com` are forwarded to the routers for the shared isolation segment.
  +* Requests for private domain `*.private-domain.com` are forwarded to the routers for IS1.
  +
  +<%= image_tag('is-distinct-domains.png') %>
  +
  +### <a id='sharing-domain'></a>Shared Domain Name
  +
  +It is a common requirement for applications on separate isolation segments to be accessible at domain names that share a domain, such as `private-apps.com`. To achieve this configuration while also obeying the guideline for forwarding requests for a domain to only one router instance group, create a new Cloud Foundry domain for a needed subdomain, such as `*.foo.private-apps.com.`
  +
  +In this configuration: 
  +
  +* Requests for system domain `*.cf-system.com` and the shared domain `*.cf-apps.com` are forwarded to the routers for the shared isolation segment.
  +* Requests for private domain `*.foo.private-domain.com` are forwarded to the routers for IS1.
  +Requests for private domain `*.private-domain.com` are forwarded to the routers for IS2.
  +
  +<%= image_tag('is-sharing-domains.png') %>
  +
  +##<a id='config-firewall'></a> Step 6: Configure Firewall Rules
  +
  +Configure firewall rules to allow necessary traffic between the shared isolation segments (`sample-shared-is`) and the private isolation segments (`sample-is1` and `sample-is2`). Assuming a default deny-all rule, these rules should prevent a request with a spoofed Host header from being forwarded by a router to an application in another isolation segment.
  +
  +<table>
  +<tr>
  +<th>Rule Name</th>
  +<th>Source subnetwork</th>
  +<th>Allowed Protocols/Ports</th>
  +<th>Target Tags</th>
  +<th>Reason</th>
  +</tr>
  +<tr>
  +<td><code>shared-to-bosh</code></td>
  +<td><code>sample-subnet-shared</code></td>
  +<td><code>tcp:22,6868,25555,<br>4222,25250<code></td>
  +<td><code>sample-bosh</code></td>
  +<td>BOSH Agent on VMs in <code>sample-shared-is</code> to reach BOSH Director</td>
  +</tr>
  +<tr>
  +<td><code>shared-internal</code></td>
  +<td><code>sample-subnet-shared</code></td>
  +<td><code>tcp</code></td>
  +<td><code>sample-shared-is</code></td>
  +<td>VMs within <code>sample-shared-is</code> to reach one another</td>
  +</tr>
  +<tr>
  +<td><code>shared-to-is1</code></td>
  +<td><code>sample-subnet-shared</code></td>
  +<td><code>tcp:1801</code></td>
  +<td><code>sample-is1</code></td>
  +<td>Diego BBS in <code>sample-shared-is</code> to reach Cells in <code>sample-is1</code></td>
  +</tr>
  +<tr>
  +<td><code>shared-to-is2</code></td>
  +<td><code>sample-subnet-shared</code></td>
  +<td><code>tcp:1801</code></td>
  +<td><code>sample-is2</code></td>
  +<td>Diego BBS in <code>sample-shared-is</code> to reach Cells in <code>sample-is2</code></td>
  +</tr>
  +<tr>
  +<td><code>is1-to-bosh</code></td>
  +<td><code>sample-subnet-is1</code></td>
  +<td><code>tcp:22,6868,25555,<br>4222,25250</code></td>
  +<td><code>sample-bosh</code></td>
  +<td>BOSH agent on VMs in <code>sample-is1</code> to reach BOSH Director</td>
  +</tr>
  +<tr>
  +<td><code>is1-internal</code></td>
  +<td><code>sample-subnet-is1</code></td>
  +<td><code>tcp</code></td>
  +<td><code>sample-is1</code></td>
  +<td>VMs within <code>sample-is1</code> to reach one another</td>
  +</tr>
  +<tr>
  +<td><code>is1-to-shared</code></td>
  +<td><code>sample-subnet-is1</code></td>
  +<td><code>tcp:8300-8500,8889,4443,9016,<br>8080,9090,3457,9022</code></td>
  +<td><code>sample-shared-is</code></td>
  +<td>Diego Cells in <code>sample-is1</code> to reach BBS and Auctioneer in <code>sample-shared-is</code>, Consul Agent to reach Consul, Metron Agent to reach Traffic Controller, and Routers to reach NATS, UAA, and Routing API</td>
  +</tr>
  +<tr>
  +<td><code>is2-to-bosh</code></td>
  +<td><code>sample-subnet-is2</code></td>
  +<td><code>tcp:22,6868,25555,<br>4222,25250</code></td>
  +<td><code>sample-bosh</code></td>
  +<td>BOSH agent on VMs in <code>sample-is2</code> to reach BOSH Director</td>
  +</tr>
  +<tr>
  +<td><code>is2-internal</code></td>
  +<td><code>sample-subnet-is2</code></td>
  +<td><code>tcp</code></td>
  +<td><code>sample-is2</code></td>
  +<td>VMs within <code>sample-is2</code> to reach one another</td>
  +</tr>
  +<tr>
  +<td><code>is2-to-shared</code></td>
  +<td><code>sample-subnet-is2</code></td>
  +<td><code>tcp:8300-8500,8889,4443,<br>9016,8080,9090,3457,9022</code></td>
  +<td><code>sample-shared-is</code></td>
  +<td>Diego Cells in <code>sample-is2</code> to reach BBS and Auctioneer in <code>sample-shared-is</code>, Consul Agent to reach Consul, Metron Agent to reach Traffic Controller, and Routers to reach NATS, UAA, and Routing API</td>
  +</tr>
  +</table>
  +
  +For more information consult the following topics:
  +
  +* The `bosh-deployment` GitHub [repo](https://github.com/cloudfoundry/bosh-deployment) contains documentation describing ports used by agents to communicate with BOSH.
  +* The "Using Subnetworks" topic in the GCP [documentation](https://cloud.google.com/compute/docs/subnetworks) describes networks and firewall rules in the "Isolation of Subnetworks" section.
  +
  +
  +## <a id='gcp-implementation'></a> Additional GCP Information
   
   For more information, see the following:
   
  
positive.code: 
  <%= image_tag('routing-is.png') %>
  
  Operators who want to prevent all isolation segments and system components from using the same network resources can deploy an additional set of routers for each isolation segment, known as a router group. Operators may want to deploy a router group to meet one of the following requirements:
  
  * Requests for applications in an isolation segment must not share networking resources with requests for other applications.
  * The Cloud Foundry management plane should only be accessible from a private network. As multiple IaaS load balancers cannot typically share the same pool of backends, such as Cloud Foundry routers, each load balancer requires an additional deployment of routers.
  
  ##<a id='create-networks'></a> Step 1: Create Networks
  
  Create a network or subnet for each isolation segment.
  
  As an example, an operator who wants one shared isolation segment and two private segments could create one network called `sample-network` with three subnets called `sample-subnet-shared`, `sample-subnet-is1`, and `sample-subnet-is2`. 
  
  
negative.code: 
  <strong><%= modified_date %></strong>
  
  This topic describes how operators can configure and manage routing for isolation segments. Operators can deploy an additional set of routers for each isolation segment to handle requests for applications within the segment.
  
  For more information about how isolation segments work, see the [Isolation Segments](../concepts/security.html#isolation-segments) section of the <em>Understanding Cloud Foundry Security</em> topic. <%= vars.install_isolation_segments %>
  
  