Chapter 4. Configuring External Services

Use this section to configure your Red Hat Satellite Capsule Server to work with external DNS, DHCP and TFTP services.

4.1. Configuring Capsule Server with External DNS

You can configure Capsule Server with external DNS. Capsule uses the nsupdate utility to update DNS records on the remote server.

To make any changes persistent, you must enter the satellite-installer command with the options appropriate for your environment.

Prerequisites

Before you can configure Capsule Server with external DNS, ensure that the following conditions are met:

  • You must have a configured external DNS server.

Procedure

To configure Capsule Server with external DNS, complete the following steps:

  1. Install the bind-utils package:

    # yum install bind bind-utils
  2. Copy the /etc/rndc.key file from the external DNS server to Capsule Server:

    # scp root@dns.example.com:/etc/rndc.key /etc/rndc.key
  3. Configure the ownership, permissions, and SELinux context:

    # restorecon -v /etc/rndc.key
    # chown -v root:named /etc/rndc.key
    # chmod -v 640 /etc/rndc.key
  4. To test the nsupdate utility, add a host remotely:

    # echo -e "server DNS_IP_Address\n \
    update add aaa.virtual.lan 3600 IN A Host_IP_Address\n \
    send\n" | nsupdate -k /etc/rndc.key
    # nslookup aaa.virtual.lan DNS_IP_Address
    # echo -e "server DNS_IP_Address\n \
    update delete aaa.virtual.lan 3600 IN A Host_IP_Address\n \
    send\n" | nsupdate -k /etc/rndc.key
  5. Enter the satellite-installer command to make the following persistent changes to the /etc/foreman-proxy/settings.d/dns.yml file:

    # satellite-installer --foreman-proxy-dns=true \
    --foreman-proxy-dns-managed=false \
    --foreman-proxy-dns-provider=nsupdate \
    --foreman-proxy-dns-server="_DNS_IP_Address_" \
    --foreman-proxy-keyfile=/etc/rndc.key \
    --foreman-proxy-dns-ttl=86400
  6. Restart the foreman-proxy service:

    # systemctl restart foreman-proxy
  7. Log in to the Satellite Server web UI and navigate to Infrastructure > Capsules.
  8. Locate the Capsule Server that you want to configure with external DNS and from the list in the Actions column, select Refresh.
  9. Associate the DNS service with the appropriate subnets and domain.

4.2. Configuring Capsule Server with External DHCP

To configure Capsule Server with external DHCP, you must complete the following procedures:

4.2.1. Configuring an External DHCP Server to Use with Capsule Server

To configure an external DHCP server to use with Capsule Server, on a Red Hat Enterprise Linux server, you must install the ISC DHCP Service and Berkeley Internet Name Domain (BIND) packages. You must also share the DHCP configuration and lease files with Capsule Server. The example in this procedure uses the distributed Network File System (NFS) protocol to share the DHCP configuration and lease files.

Procedure

To configure an external DHCP server to use with Capsule Server, complete the following steps:

  1. On a Red Hat Enterprise Linux Server server, install the ISC DHCP Service and Berkeley Internet Name Domain (BIND) packages:

    # yum install dhcp bind
  2. Generate a security token:

    # dnssec-keygen -a HMAC-MD5 -b 512 -n HOST omapi_key

    As a result, a key pair that consists of two files is created in the current directory.

  3. Copy the secret hash from the key:

    # cat Komapi_key.+*.private |grep ^Key|cut -d ' ' -f2
  4. Edit the dhcpd configuration file for all of the subnets and add the key. The following is an example:

    # cat /etc/dhcp/dhcpd.conf
    default-lease-time 604800;
    max-lease-time 2592000;
    log-facility local7;
    
    subnet 192.168.38.0 netmask 255.255.255.0 {
    	range 192.168.38.10 192.168.38.100;
    	option routers 192.168.38.1;
    	option subnet-mask 255.255.255.0;
    	option domain-search "virtual.lan";
    	option domain-name "virtual.lan";
    	option domain-name-servers 8.8.8.8;
    }
    
    omapi-port 7911;
    key omapi_key {
    	algorithm HMAC-MD5;
    	secret "jNSE5YI3H1A8Oj/tkV4...A2ZOHb6zv315CkNAY7DMYYCj48Umw==";
    };
    omapi-key omapi_key;

    Note that the option routers value is the Satellite or Capsule IP address that you want to use with an external DHCP service.

  5. Delete the two key files from the directory that they were created in.
  6. On Satellite Server, define each subnet. Do not set DHCP Capsule for the defined Subnet yet.

    To prevent conflicts, set up the lease and reservation ranges separately. For example, if the lease range is 192.168.38.10 to 192.168.38.100, in the Satellite web UI define the reservation range as 192.168.38.101 to 192.168.38.250.

  7. Configure the firewall for external access to the DHCP server:

    # firewall-cmd --add-service dhcp \
    && firewall-cmd --runtime-to-permanent
  8. On Satellite Server, determine the UID and GID of the foreman user:

    # id -u foreman
    993
    # id -g foreman
    990
  9. On the DHCP server, create the foreman user and group with the same IDs as determined in a previous step:

    # groupadd -g 990 foreman
    # useradd -u 993 -g 990 -s /sbin/nologin foreman
  10. To ensure that the configuration files are accessible, restore the read and execute flags:

    # chmod o+rx /etc/dhcp/
    # chmod o+r /etc/dhcp/dhcpd.conf
    # chattr +i /etc/dhcp/ /etc/dhcp/dhcpd.conf
  11. Start the DHCP service:

    # systemctl start dhcpd
  12. Export the DHCP configuration and lease files using NFS:

    # yum install nfs-utils
    # systemctl enable rpcbind nfs-server
    # systemctl start rpcbind nfs-server nfs-lock nfs-idmapd
  13. Create directories for the DHCP configuration and lease files that you want to export using NFS:

    # mkdir -p /exports/var/lib/dhcpd /exports/etc/dhcp
  14. To create mount points for the created directories, add the following line to the /etc/fstab file:

    /var/lib/dhcpd /exports/var/lib/dhcpd none bind,auto 0 0
    /etc/dhcp /exports/etc/dhcp none bind,auto 0 0
  15. Mount the file systems in /etc/fstab:

    # mount -a
  16. Ensure the following lines are present in /etc/exports:

    /exports 192.168.38.1(rw,async,no_root_squash,fsid=0,no_subtree_check)
    
    /exports/etc/dhcp 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)
    
    /exports/var/lib/dhcpd 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)

    Note that the IP address that you enter is the Satellite or Capsule IP address that you want to use with an external DHCP service.

  17. Reload the NFS server:

    # exportfs -rva
  18. Configure the firewall for the DHCP omapi port 7911:

    # firewall-cmd --add-port="7911/tcp" \
    && firewall-cmd --runtime-to-permanent
  19. Optional: Configure the firewall for external access to NFS.

    Clients are configured using NFSv3.

    • Use the firewalld NFS service to configure the firewall:

      # firewall-cmd --zone public --add-service mountd \
      && firewall-cmd --zone public --add-service rpc-bind \
      && firewall-cmd --zone public --add-service nfs \
      && firewall-cmd --runtime-to-permanent

4.2.2. Configuring Capsule Server with an External DHCP Server

You can configure Capsule Server with an external DHCP server.

Prerequisite

Procedure

To configure Capsule Server with external DHCP, complete the following steps:

  1. Install the nfs-utils utility:

    # yum install nfs-utils
  2. Create the DHCP directories for NFS:

    # mkdir -p /mnt/nfs/etc/dhcp /mnt/nfs/var/lib/dhcpd
  3. Change the file owner:

    # chown -R foreman-proxy /mnt/nfs
  4. Verify communication with the NFS server and the Remote Procedure Call (RPC) communication paths:

    # showmount -e DHCP_Server_FQDN
    # rpcinfo -p DHCP_Server_FQDN
  5. Add the following lines to the /etc/fstab file:

    DHCP_Server_FQDN:/exports/etc/dhcp /mnt/nfs/etc/dhcp nfs
    ro,vers=3,auto,nosharecache,context="system_u:object_r:dhcp_etc_t:s0" 0 0
    
    DHCP_Server_FQDN:/exports/var/lib/dhcpd /mnt/nfs/var/lib/dhcpd nfs
    ro,vers=3,auto,nosharecache,context="system_u:object_r:dhcpd_state_t:s0" 0 0
  6. Mount the file systems on /etc/fstab:

    # mount -a
  7. To verify that the foreman-proxy user can access the files that are shared over the network, display the DHCP configuration and lease files:

    # su foreman-proxy -s /bin/bash
    bash-4.2$ cat /mnt/nfs/etc/dhcp/dhcpd.conf
    bash-4.2$ cat /mnt/nfs/var/lib/dhcpd/dhcpd.leases
    bash-4.2$ exit
  8. Enter the satellite-installer command to make the following persistent changes to the /etc/foreman-proxy/settings.d/dhcp.yml file:

    # satellite-installer --foreman-proxy-dhcp=true \
    --foreman-proxy-dhcp-provider=remote_isc \
    --foreman-proxy-plugin-dhcp-remote-isc-dhcp-config /mnt/nfs/etc/dhcp/dhcpd.conf \
    --foreman-proxy-plugin-dhcp-remote-isc-dhcp-leases /mnt/nfs/var/lib/dhcpd/dhcpd.leases \
    --foreman-proxy-plugin-dhcp-remote-isc-key-name=omapi_key \
    --foreman-proxy-plugin-dhcp-remote-isc-key-secret=jNSE5YI3H1A8Oj/tkV4...A2ZOHb6zv315CkNAY7DMYYCj48Umw== \
    --foreman-proxy-plugin-dhcp-remote-isc-omapi-port=7911 \
    --enable-foreman-proxy-plugin-dhcp-remote-isc \
    --foreman-proxy-dhcp-server=DHCP_Server_FQDN
  9. Restart the foreman-proxy service:

    # systemctl restart foreman-proxy
  10. Log in to the Satellite Server web UI.
  11. Navigate to Infrastructure > Capsules. Locate the Capsule Server that you want to configure with external DHCP, and from the list in the Actions column, select Refresh.
  12. Associate the DHCP service with the appropriate subnets and domain.

4.3. Configuring Capsule Server with External TFTP

You can configure Capsule Server with external TFTP services.

Procedure

To configure Capsule Server with external TFTP, complete the following steps:

  1. Create the TFTP directory for NFS:

    # mkdir -p /mnt/nfs/var/lib/tftpboot
  2. In the /etc/fstab file, add the following line:

    TFTP_Server_IP_Address:/exports/var/lib/tftpboot /mnt/nfs/var/lib/tftpboot nfs rw,vers=3,auto,nosharecache,context="system_u:object_r:tftpdir_rw_t:s0" 0 0
  3. Mount the file systems in /etc/fstab:

    # mount -a
  4. Enter the satellite-installer command to make the following persistent changes to the /etc/foreman-proxy/settings.d/tftp.yml file:

    # satellite-installer --foreman-proxy-tftp=true \
    --foreman-proxy-tftp-root /mnt/nfs/var/lib/tftpboot
  5. If the TFTP service is running on a different server than the DHCP service, update the tftp_servername setting with the FQDN or IP address of the server that the TFTP service is running on:

    # satellite-installer --foreman-proxy-tftp-servername=TFTP_Server_FQDN
  6. Log in to the Satellite Server web UI.
  7. Navigate to Infrastructure > Capsules. Locate the appropriate Capsule Server and from the list in the Actions column, select Refresh.
  8. Associate the TFTP service with the appropriate subnets and domain.

4.4. Configuring Satellite or Capsule with External IdM DNS

Red Hat Satellite can be configured to use a Red Hat Identity Management (IdM) server to provide the DNS service. Two methods are described here to achieve this, both using a transaction key. For more information on Red Hat Identity Management, see the Linux Domain Identity, Authentication, and Policy Guide.

The first method is to install the IdM client which automates the process with the generic security service algorithm for secret key transaction (GSS-TSIG) technology defined in RFC3645. This method requires installing the IdM client on the Satellite Server or Capsule’s base system and having an account created by the IdM server administrator for use by the Satellite administrator. See Section 4.4.1, “Configuring Dynamic DNS Update with GSS-TSIG Authentication” to use this method.

The second method, secret key transaction authentication for DNS (TSIG), uses an rndc.key for authentication. It requires root access to the IdM server to edit the BIND configuration file, installing the BIND utility on the Satellite Server’s base system, and coping the rndc.key to between the systems. This technology is defined in RFC2845. See Section 4.4.2, “Configuring Dynamic DNS Update with TSIG Authentication” to use this method.

Note

You are not required to use Satellite to manage DNS. If you are using the Realm enrollment feature of Satellite, where provisioned hosts are enrolled automatically to IdM, then the ipa-client-install script creates DNS records for the client. The following procedure and Realm enrollment are therefore mutually exclusive. For more information on configuring Realm enrollment, see External Authentication for Provisioned Hosts in Administering Red Hat Satellite.

Determining where to install the IdM Client

When Satellite Server wants to add a DNS record for a host, it first determines which Capsule is providing DNS for that domain. It then communicates with the Capsule and adds the record. The hosts themselves are not involved in this process. This means you should install and configure the IdM client on the Satellite or Capsule that is currently configured to provide a DNS service for the domain you want to manage using the IdM server.

4.4.1. Configuring Dynamic DNS Update with GSS-TSIG Authentication

In this example, Satellite Server has the following settings.

Host name

satellite.example.com

Network

192.168.55.0/24

The IdM server has the following settings.

Host name

idm1.example.com

Domain name

example.com

Before you Begin.

  1. Confirm the IdM server is deployed and the host-based firewall has been configured correctly. For more information, see Port Requirements in the Linux Domain Identity, Authentication, and Policy Guide.
  2. Obtain an account on the IdM server with permissions to create zones on the IdM server.
  3. Confirm if the Satellite or an external Capsule is managing DNS for a domain.
  4. Confirm that the Satellite or external Capsule are currently working as expected.
  5. In the case of a newly installed system, complete the installation procedures in this guide first. In particular, DNS and DHCP configuration should have been completed.
  6. Make a backup of the answer file in case you have to revert the changes. See Specifying Installation Options for more information.

Create a Kerberos Principal on the IdM Server.

  1. Ensure you have a Kerberos ticket.

    # kinit idm_user

    Where idm_user is the account created for you by the IdM administrator.

  2. Create a new Kerberos principal for the Satellite or Capsule to use to authenticate to the IdM server.

    # ipa service-add capsule/satellite.example.com

Install and Configure the IdM Client.

Do this on the Satellite or Capsule Server that is managing the DNS service for a domain.

  1. Install the ipa-client package on Satellite Server or Capsule Server:

    • On Satellite Server, enter the following command:

      # satellite-maintain packages install ipa-client
    • On Capsule Server, enter the following command:

      # yum install ipa-client
  2. Configure the IdM client by running the installation script and following the on-screen prompts.

    # ipa-client-install
  3. Ensure you have a Kerberos ticket.

    # kinit admin
  4. Remove any preexisting keytab.

    # rm /etc/foreman-proxy/dns.keytab
  5. Get the keytab created for this system.

    # ipa-getkeytab -p capsule/satellite.example.com@EXAMPLE.COM \
    -s idm1.example.com -k /etc/foreman-proxy/dns.keytab
    Note

    When adding a keytab to a standby system with the same host name as the original system in service, add the r option to prevent generating new credentials and rendering the credentials on the original system invalid.

  6. Set the group and owner for the keytab file to foreman-proxy as follows.

    # chown foreman-proxy:foreman-proxy /etc/foreman-proxy/dns.keytab
  7. If required, check the keytab is valid.

    # kinit -kt /etc/foreman-proxy/dns.keytab \
    capsule/satellite.example.com@EXAMPLE.COM

Configure DNS Zones in the IdM web UI.

  1. Create and configure the zone to be managed:

    1. Navigate to Network Services > DNS > DNS Zones.
    2. Select Add and enter the zone name. In this example, example.com.
    3. Click Add and Edit.
    4. On the Settings tab, in the BIND update policy box, add an entry as follows to the semi-colon separated list.

      grant capsule\047satellite.example.com@EXAMPLE.COM wildcard * ANY;
    5. Ensure Dynamic update is set to True.
    6. Enable Allow PTR sync.
    7. Select Save to save the changes.
  2. Create and Configure the reverse zone.

    1. Navigate to Network Services > DNS > DNS Zones.
    2. Select Add.
    3. Select Reverse zone IP network and add the network address in CIDR format to enable reverse lookups.
    4. Click Add and Edit.
    5. On the Settings tab, in the BIND update policy box, add an entry as follows to the semi-colon separated list:

      grant capsule\047satellite.example.com@EXAMPLE.COM wildcard * ANY;
    6. Ensure Dynamic update is set to True.
    7. Select Save to save the changes.

Configure the Satellite or Capsule Server Managing the DNS Service for the Domain.

  • On a Satellite Server’s Base System.

    satellite-installer --scenario satellite \
    --foreman-proxy-dns=true \
    --foreman-proxy-dns-managed=true \
    --foreman-proxy-dns-provider=nsupdate_gss \
    --foreman-proxy-dns-server="idm1.example.com" \
    --foreman-proxy-dns-tsig-principal="capsule/satellite.example.com@EXAMPLE.COM" \
    --foreman-proxy-dns-tsig-keytab=/etc/foreman-proxy/dns.keytab \
    --foreman-proxy-dns-reverse="55.168.192.in-addr.arpa" \
    --foreman-proxy-dns-zone=example.com \
    --foreman-proxy-dns-ttl=86400
  • On a Capsule Server’s Base System.

    satellite-installer --scenario capsule \
    --foreman-proxy-dns=true \
    --foreman-proxy-dns-managed=true \
    --foreman-proxy-dns-provider=nsupdate_gss \
    --foreman-proxy-dns-server="idm1.example.com" \
    --foreman-proxy-dns-tsig-principal="capsule/satellite.example.com@EXAMPLE.COM" \
    --foreman-proxy-dns-tsig-keytab=/etc/foreman-proxy/dns.keytab \
    --foreman-proxy-dns-reverse="55.168.192.in-addr.arpa" \
    --foreman-proxy-dns-zone=example.com \
    --foreman-proxy-dns-ttl=86400

Restart the Satellite or Capsule’s Proxy Service.

# systemctl restart foreman-proxy

Update the Configuration in Satellite web UI.

After you have run the installation script to make any changes to a Capsule, instruct Satellite to scan the configuration on each affected Capsule as follows:

  1. Navigate to Infrastructure > Capsules.
  2. For each Capsule to be updated, from the Actions drop-down menu, select Refresh.
  3. Configure the domain:

    1. Go to Infrastructure > Domains and select the domain name.
    2. On the Domain tab, ensure DNS Capsule is set to the Capsule where the subnet is connected.
  4. Configure the subnet:

    1. Go to Infrastructure > Subnets and select the subnet name.
    2. On the Subnet tab, set IPAM to None.
    3. On the Domains tab, ensure the domain to be managed by the IdM server is selected.
    4. On the Capsules tab, ensure Reverse DNS Capsule is set to the Capsule where the subnet is connected.
    5. Click Submit to save the changes.

4.4.2. Configuring Dynamic DNS Update with TSIG Authentication

In this example, Satellite Server has the following settings.

IP address

192.168.25.1

Host name

satellite.example.com

The IdM server has the following settings.

Host name

idm1.example.com

IP address

192.168.25.2

Domain name

example.com

Before you Begin

  1. Confirm the IdM Server is deployed and the host-based firewall has been configured correctly. For more information, see Port Requirements in the Linux Domain Identity, Authentication, and Policy Guide.
  2. Obtain root user privileges on the IdM server.
  3. Confirm if the Satellite or an external Capsule is managing DNS for a domain.
  4. Confirm that the Satellite or external Capsule are currently working as expected.
  5. In the case of a newly installed system, complete the installation procedures in this guide first. In particular, DNS and DHCP configuration should have been completed.
  6. Make a backup of the answer file in case you have to revert the changes. See Specifying Installation Options for more information.

Enabling External Updates to the DNS Zone in the IdM Server

  1. On the IdM Server, add the following to the top of the /etc/named.conf file.

    // This was added to allow Satellite Server at 192.168.25.1 to make DNS updates.
    ########################################################################
    include "/etc/rndc.key";
    controls  {
    inet 192.168.25.2 port 953 allow { 192.168.25.1; } keys { "rndc-key"; };
    };
    ########################################################################
  2. Reload named to make the changes take effect.

    # systemctl reload named
  3. In the IdM web UI, go to Network Services > DNS > DNS Zones. Select the name of the zone. On the Settings tab:

    1. Add the following in the BIND update policy box.

      grant "rndc-key" zonesub ANY;
    2. Ensure Dynamic update is set to True.
    3. Click Update to save the changes.
  4. Copy the /etc/rndc.key file from the IdM server to Satellite’s base system as follows.

    # scp /etc/rndc.key root@satellite.example.com:/etc/rndc.key
  5. Ensure that the ownership, permissions, and SELinux context are correct.

    # restorecon -v /etc/rndc.key
    # chown -v root:named /etc/rndc.key
    # chmod -v 640 /etc/rndc.key
  6. On Satellite Server, run the installation script as follows to use the external DNS server.

    # satellite-installer --scenario satellite \
    --foreman-proxy-dns=true \
    --foreman-proxy-dns-managed=false \
    --foreman-proxy-dns-provider=nsupdate \
    --foreman-proxy-dns-server="192.168.25.2" \
    --foreman-proxy-keyfile=/etc/rndc.key \
    --foreman-proxy-dns-ttl=86400

Testing External Updates to the DNS Zone in the IdM Server

  1. Install bind-utils for testing with nsupdate.

    # yum install bind-utils
  2. Ensure the key in the /etc/rndc.key file on Satellite Server is the same one as used on the IdM server.

    key "rndc-key" {
            algorithm hmac-md5;
            secret "secret-key==";
    };
  3. On Satellite Server, create a test DNS entry for a host. For example, host test.example.com with an A record of 192.168.25.20 on the IdM server at 192.168.25.1.

    # echo -e "server 192.168.25.1\n \
    update add test.example.com 3600 IN A 192.168.25.20\n \
    send\n" | nsupdate -k /etc/rndc.key
  4. On Satellite Server, test the DNS entry.

    # nslookup test.example.com 192.168.25.1
    Server:		192.168.25.1
    Address:	192.168.25.1#53
    
    Name:	test.example.com
    Address: 192.168.25.20
  5. To view the entry in the IdM web UI, go to Network Services > DNS > DNS Zones. Select the name of the zone and search for the host by name.
  6. If resolved successfully, remove the test DNS entry.

    # echo -e "server 192.168.25.1\n \
    update delete test.example.com 3600 IN A 192.168.25.20\n \
    send\n" | nsupdate -k /etc/rndc.key
  7. Confirm that the DNS entry was removed.

    # nslookup test.example.com 192.168.25.1

    The above nslookup command fails and returns the SERVFAIL error message if the record was successfully deleted.

4.4.3. Reverting to Internal DNS Service

To revert to using Satellite Server and Capsule Server as DNS providers, follow this procedure.

On the Satellite or Capsule Server that is to manage DNS for the domain.

  • If you backed up the answer file before the change to external DNS, restore the answer file and then run the installation script:

    # satellite-installer
  • If you do not have a suitable backup of the answer file, back up the answer file now, and then run the installation script on Satellite and Capsules as described below.

    See Specifying Installation Options for more information on the answer file.

To configure Satellite or Capsule as DNS server without using an answer file.

# satellite-installer \
--foreman-proxy-dns=true \
--foreman-proxy-dns-managed=true \
--foreman-proxy-dns-provider=nsupdate \
--foreman-proxy-dns-server="127.0.0.1"  \
--foreman-proxy-dns-tsig-principal="foremanproxy/satellite.example.com@EXAMPLE.COM" \
--foreman-proxy-dns-tsig-keytab=/etc/foreman-proxy/dns.keytab

See Configuring DNS, DHCP, and TFTP on Capsule Server for more information.

Update the Configuration in Satellite web UI.

After you have run the installation script to make any changes to a Capsule, instruct Satellite to scan the configuration on each affected Capsule as follows:

  1. Navigate to Infrastructure > Capsules.
  2. For each Capsule to be updated, from the Actions drop-down menu, select Refresh.
  3. Configure the domain:

    1. Go to Infrastructure > Domains and select the domain name.
    2. On the Domain tab, ensure DNS Capsule is set to the Capsule where the subnet is connected.
  4. Configure the subnet:

    1. Go to Infrastructure > Subnets and select the subnet name.
    2. On the Subnet tab, set IPAM to DHCP or Internal DB.
    3. On the Domains tab, ensure the domain to be managed by the Satellite or Capsule is selected.
    4. On the Capsules tab, ensure Reverse DNS Capsule is set to the Capsule where the subnet is connected.
    5. Click Submit to save the changes.