Lab 6: IGMP Snooping
Learning Objectives:
· Observe IGMP snooping behavior on the switch
N.B. This lab requires three student laptops plugged into the HP ProCurve switch. The laptops need tcpdump or Wireshark and rtpqual or some other multicast receive program installed (e.g. iperf).
Questions to keep in mind while you perform this lab:
· Did the third student laptop see any multicast traffic? IGMP?
· Did the first or second laptops see their membership reports?
· When the first laptop left, did traffic stop flowing to it? Immediately?
· When the second laptop left, did traffic stop flowing to it? The first? Immediately?
· Take a close look at the General and Group-Specific IGMP queries.
· Are they from the router or the switch? (Look at the MAC address.)
Compare the timing of IGMP events on the router vs. those on the switch.
Step 1: Configure Switch
§ Make sure HP ProCurve switch has IGMP snooping enabled.
telnet 206.244.x.194
HP ProCurve Switch 2626# conf t
HP ProCurve Switch 2626(config)# vlan 1
HP ProCurve Switch 2626(config)# ip igmp
HP ProCurve Switch 2626(config)# end
Step 2: Configure customer-D
§ Interface fa1/0 (which is connected to switch) for IGMP v2
int FastEthernet1/0
ip igmp version 2
end
§ Turn on IGMP debugging messages
# term mon
# debug ip igmp <group>
Step 3: Start a multicast source on host Q or R.
iperf –u –c <group> -p <port> -b 1 -T 10 –t 1000
Step 4: Start Wireshark on three student laptops.
wireshark
Capture -> Start -> Filter: igmp or dst <group> -> OK
Step 5: Check IGMP snooping state on switch (repeat periodically).
HP ProCurve Switch 2626# show ip igmp group <group>
Step 6: Check IGMP state on Customer-D router (repeat periodically).
p1d# show ip igmp group <group>
Step 7: Start receivers
§ on first student laptop…
./rtpqual <group> <port>
or
iperf –s –i 1 –u –B <group> -p <port>
§ Wait about a minute and start receiver on second student laptop
§ Wait another minute and stop receiver on first student laptop
§ Wait another minute and stop receiver on second student laptop
§ Keep watching Wireshark, switch and router consoles until IGMP and traffic flows stop
§ Repeat above with IGMP version 3 (allow some time after switching from IGMP v2 to v3 on the router before starting your test so the hosts can hear the periodic IGMP v3 General Query).
Step 7: Move the source
§ Now move the source to one of the hosts attached to the switch.
§ Observe the traffic for the following cases:
o No other hosts on the switch join the group.
o A host joins the group.
o That host leaves the group.
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Revised 3/27/08 Page