Based on feedback here and in classes since that post, I've learned most people don't care about building sensors. They are more interested in analysis. Therefore, I decided students didn't need dedicated VMs. Therefore, I could run a few VMs with dedicated functions, and let students share systems as normal users. For example, in my last class a dozen students all logged in to a single FreeBSD image to perform analysis.
In the future, I plan to have multiple images running. For example, I plan to offer several complete Sguil installations. Students in groups of two or four might share one Sguil server. My current test environment uses VMWare Workstation 5 running 6 FreeBSD 5.4 REL images simultaneously.
Since VMWare 3.x I've wondered about the product's networking support. For example, if I provided a set of VMs with internal NICs, could they see each other's traffic? I decided to answer this question by putting my 6 FreeBSD VMs into a single VM "team", as shown.
One interface (lnc0 on each) is bridged so I can access the systems remotely. The second interface (lnc1 on each) is limited to the team and is addressed with an internal scheme. Here is the question: if freebsd54-rel_01 pings freebsd54-rel_02, will freebsd54-rel_03 see it? Here is the ping:
$ ping -c 1 10.1.1.202
PING 10.1.1.202 (10.1.1.202): 56 data bytes
64 bytes from 10.1.1.202: icmp_seq=0 ttl=64 time=2.943 ms
--- 10.1.1.202 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 2.943/2.943/2.943/0.000 ms
Here is what another system on the team sees:
fbsd5403# tcpdump -n -i lnc1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lnc1, link-type EN10MB (Ethernet), capture size 96 bytes
08:19:58.946640 IP 10.1.1.201 > 10.1.1.202: icmp 64: echo request seq 0
08:19:58.946695 IP 10.1.1.202 > 10.1.1.201: icmp 64: echo reply seq 0
Yes. That is great. Life is much simpler now, since any machine can see any other machine on the same team. That facilitates setting up networks that can be monitored.