igmp best practices

[RobB_8]

I am trying to understand IGMP a little better and I stumbled on some info re IGMP on the HP site that suggesed turning on IGMP on all vlans if you do imaging. The question is, is it necessary to do it on all switches/ or does it make sense to limit it to only switches that you anticipate doing multicast images from? Also the recommendation was to turn it on for "most vlans"... the question is under what circumstances would you not want to turn it on?
Thanks

[Matt Hobbs · Accepted solution]

Personally I would enable it on every VLAN on every switch. Right now I can't think of a situation where you should not enable it. I'd be interested to see anyone else's opinion on this.

[Jonathan Axford]

I agree with Matt, i have always been under the impression that there is no harm in turning it on, so why not do it!

[RobB_8]

I have tried rolling it out to a few sites and I am now receiving complaints:
1) the site that is novell, now cannot browse the tree, but can login if they specify the IP of the server
2) the site that is Win2k Domain is now very very slow at login
Has anyone seen this?

[OLARU Dan]

We too do imaging, but not very often. What I did was to put "ip helper-address a.b.c.d" to the server that distributes images on all VLAN interfaces that host the users in the inter-VLAN router.

As you turn on more features on the switches, these new routines take up more of the switch resources from the normal switching processes; some new-feature routines tend to have bugs, which also take up resources. Many vendors use non-standard, proprietary solutions for these features (for vendor-lockin purposes: too bad the free software community is not yet interested in firmware business, altough the movement was started by Stallman due to printer software becoming closed) - so inter-op is not possible. No vendor will tell you which is the optimal set of features that you should turn on and still have the device perform its main function optimally. It's a trial-and-error process.

I tried routing on 4108; it made the device very slow, so I dropped it and I acquired an true-L3 device for inter-VLAN routing. I tried STP on my population of HP managed switches; it made the printers work extremely slow, so I dropped it for normal operation. After I tell all users that the network will be slow for 1 hour, I turn STP on during major moves-adds-changes to check for loops, but I turn it off 15 minutes later, when I am certain no there is loop.

I hope this perspective will help you in your best-practices endeavour, Rob.

Cheers,
Dan