Adds scaled env. for multicast testing.

Env. can support at most 4 aggregation switches (controlled by --a).
Each aggregation device has 48 ports.

netcfg is autogenerated by trellis_mcast_netcfg_gen.py.

Additionally, makes the sleep configurable,
puts in background dhclient, improves .gitignore
and extends dhcp configs.

Change-Id: I03bd0d3e94767b6b8846653989e5f9c452e7dc65
diff --git a/trellis/dhcpd6.conf b/trellis/dhcpd6.conf
index dccb5ec..6910e4c 100644
--- a/trellis/dhcpd6.conf
+++ b/trellis/dhcpd6.conf
@@ -36,6 +36,25 @@
   option dhcp6.next-hop 2000::bff;
 }
 
+subnet6 2002::100/120 {
+  range6 2002::160 2002::1fe;
+  option dhcp6.next-hop 2002::1ff;
+}
+
+subnet6 2002::200/120 {
+  range6 2002::260 2002::2fe;
+  option dhcp6.next-hop 2002::2ff;
+}
+
+subnet6 2002::300/120 {
+  range6 2002::360 2002::3fe;
+  option dhcp6.next-hop 2002::3ff;
+}
+
+subnet6 2002::400/120 {
+  range6 2002::460 2002::4fe;
+  option dhcp6.next-hop 2002::4ff;
+}
 
 host h1v6 {
   hardware ethernet 00:bb:00:00:00:01;