Commit 18b9688f authored by Robert Ricci's avatar Robert Ricci

Add notes about multicast and multiple switches.

parent fe1c9022
......@@ -26,7 +26,7 @@ causing the DHCP to take much longer than necessary.
##### Reducing stray traffic
Disable spanning tree (STP.) If on, STP sends out pakcets approximately every
Disable spanning tree (STP.) If on, STP sends out packets approximately every
two seconds on every port. You can disable it on all VLANs with the command
set spantree disable all
There are two major consequences (for our purposes) of disabling STP:
......@@ -80,3 +80,25 @@ booting process leaves the nodes sitting dormant at a boot loader for extended
periods of time, so the switch will tend to forget their MACs. Turning off
aging is not critical, but we suggest it, because it will reduce stray traffic
while the switch re-learns MAC addresses.
##### Setting up multicast between multiple switches
If you have more than one switch on the experimental or control networks, you
may need to do a little setup to get multicast between them. The symptom of
this problem is that multicast doesn't work between two nodes on different
switches, and if you run 'show multicast groups' on each switch, some will show
the group as existing, and others will not.
Run the following command for both sides (ie. on both switches) of every trunk
link:
set multicast router 1/1
(assuming that port 1/1 is your trunk link). If you are using EtherChannel to
bond together multiple links to form a single trunk, you only need to run this
command for the first port in the channel.
We had some problems running this command on the trunk on one of our switches:
it failed with the error:
Failed to add port 2/1 to multicast router port list.
What I finally did to resolve this was to tear down the trunk link and
EtherChannel that port was a part of, run the command on it (which succeeded
this time), and then build the EtherChannel and trunk back up.
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