Post Thu Jun 06, 2013 11:58 am

Slow MultiCast Imaging with Symantec Ghost

I'm running MultiCast Imaging with Symantec Ghost. The image I'm pushing out is 500GB. It was taking me over 24 hours to push the image out as I was only getting 200MB per minute.

My network was gigabit with a HP ProCurve Switch 2810-48G switch and gigabit NIC's in all the workstations.

Why was it going so slow?

After doing some research I found out that the HP switches have IGMP (Internet Group Management Protocol) disabled by default. IGMP is used to manage the membership of Internet Protocol multicast groups. A ghost cast session is an IGMP group, workstations need to join the IGMP session on the switch to participate in IGMP group traffic. When IGMP is disabled on the switch, the switch treats the multicast traffic as broadcast traffic sending it out over all ports in the specified VLAN - meaning every PC on the network receives the communication. Every PC or device on the VLAN recieves every packet sent from the ghost cast session as they do not have an application listening on the specified port; they will drop the packets.

This network is one big VLAN. Some devices on the VLAN could not support high speed network connectivity even though they had a gigabit NIC. One of these devices was a PACom WebGuard Camera Video Surveillance system. This Camera System was also receiving every packet from the ghost cast session - however because it is not designed to deal with such a large amount of data it was dropping packets meaning the ghostcast server needed to slow down to ensure every PC on the network received the data. A broadcast will only go the speed of the slowest device on the network. Bad cables will also effect the speed of the broadcast. Multicasts have the same principal, they will only go the speed of the slowest device in its multicast group, however you have narrowed it down to a group of devices instead of all devices in a specified VLAN.

To enable IGMP on a VLAN you just enter ip igmp into the switches config under the right area:

ProCurve Switch 2810-48G# show run

Running configuration:

; J9022A Configuration Editor; Created on release #N.11.15

hostname "ProCurve Switch 2810-48G"
snmp-server contact "Clint Boessen"
ip default-gateway
snmp-server community "public" Unrestricted
vlan 1
untagged 1-48
ip address
ip igmp
password manager