diff --git a/tcp_tests/templates/salt/mk22-qa-lab01-salt.yaml b/tcp_tests/templates/salt/mk22-qa-lab01-salt.yaml
index c559d54..0f2e81d 100644
--- a/tcp_tests/templates/salt/mk22-qa-lab01-salt.yaml
+++ b/tcp_tests/templates/salt/mk22-qa-lab01-salt.yaml
@@ -124,6 +124,19 @@
   retry: {count: 3, delay: 10}
   skip_fail: false
 
+- description: * Workaround for VMs: set low 'max_heap_size' for Cassandra
+  cmd: |
+    cat << 'EOF' >> /srv/salt/reclass/classes/system/linux/system/single.yml
+    # opencontrail lowmem
+      opencontrail:
+        database:
+          max_heap_size: "1G"
+          heap_newsize: "200M"
+    EOF
+  node_name: cfg01.mk22-qa-lab01.local
+  retry: {count: 1, delay: 1}
+  skip_fail: false
+
 
 # Prepare salt services and nodes settings
 - description: Run 'linux' formula on cfg01
diff --git a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data-cfg01.yaml b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data-cfg01.yaml
index 31f60a7..c90e6ad 100644
--- a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data-cfg01.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data-cfg01.yaml
@@ -48,7 +48,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1404.yaml b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1404.yaml
index 669627d..b337f0c 100644
--- a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1404.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1404.yaml
@@ -90,7 +90,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto eth0
           iface eth0 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1604.yaml b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1604.yaml
index 4951802..bf1ea31 100644
--- a/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1604.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-advanced--user-data1604.yaml
@@ -83,7 +83,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-lab-basic--user-data-cfg01.yaml b/tcp_tests/templates/underlay/mk22-lab-basic--user-data-cfg01.yaml
index 31f60a7..c90e6ad 100644
--- a/tcp_tests/templates/underlay/mk22-lab-basic--user-data-cfg01.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-basic--user-data-cfg01.yaml
@@ -48,7 +48,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-lab-basic--user-data1404.yaml b/tcp_tests/templates/underlay/mk22-lab-basic--user-data1404.yaml
index 8df02af..faadbb5 100644
--- a/tcp_tests/templates/underlay/mk22-lab-basic--user-data1404.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-basic--user-data1404.yaml
@@ -90,7 +90,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto eth0
           iface eth0 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-lab-basic--user-data1604.yaml b/tcp_tests/templates/underlay/mk22-lab-basic--user-data1604.yaml
index 4ec3a67..ff6539a 100644
--- a/tcp_tests/templates/underlay/mk22-lab-basic--user-data1604.yaml
+++ b/tcp_tests/templates/underlay/mk22-lab-basic--user-data1604.yaml
@@ -86,7 +86,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data-cfg01.yaml b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data-cfg01.yaml
index 31f60a7..c90e6ad 100644
--- a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data-cfg01.yaml
+++ b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data-cfg01.yaml
@@ -48,7 +48,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1404.yaml b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1404.yaml
index 8df02af..faadbb5 100644
--- a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1404.yaml
+++ b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1404.yaml
@@ -90,7 +90,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto eth0
           iface eth0 inet dhcp
diff --git a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1604.yaml b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1604.yaml
index 4ec3a67..ff6539a 100644
--- a/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1604.yaml
+++ b/tcp_tests/templates/underlay/mk22-qa-lab01--user-data1604.yaml
@@ -86,7 +86,7 @@
    ########################################################
 
   write_files:
-   - path: /etc/network/interfaces.d/99-tcp-tests.cfg
+   - path: /etc/network/interfaces
      content: |
           auto ens3
           iface ens3 inet dhcp