Commit 0b7190f1 authored by Robert Ricci's avatar Robert Ricci

Add notes about the IP helper address, which is used to forward DHCP

traffic between subnets
parent 58c2a25b
##### Configuration suggestions for Cisco switches
##### Last updated April 5, 2002
##### Last updated July 25, 2002
The purpose of this document is to aid in designing and setting up the control
and experimental networks on other emulabs.
......@@ -80,6 +80,20 @@ the default one. However, you want to make sure that no ports on the nodes can
talk to it, so you'll want to disable them all. (Our software will re-enable
them, and disable them as needed.)
##### DHCP through the router
If your boss node is on a seperate VLAN from the node control net, you'll need
to make sure that DHCP traffic can get from the control net to your boss node,
since normally, DHCP is not forwarded through routers. On Cisco routers, this
is done with the 'ip helper-address'. For example, here, the name of the
router's interface in the node control net is 'Vlan3'. So, I'd log into the
router, and run the following:
configure terminal
interface Vlan3
ip helper-address
Of course, replace 'Vlan3' with the name of your router's node
control-net interface, and replace the IP address with that of your boss node.
##### Some variations on the above configuration
There are some variations on the above configuration that we haven't tried, but
......@@ -96,6 +110,7 @@ As an added measure of security on the experimental network, you could move
your switch IP interfaces (and the wire that runs from them to the control net)
out of VLAN 1. When ports are not in use, we put them in VLAN 1 and disable
them. But, if a port accidentally ends up in VLAN 1 still enabled, it could
theoretically talk to the switch and change configurations.
theoretically talk to the switch and change configurations. Furthermore, we've
had circumstances in which delay nodes accidentally ended up in tis VLAN, still
forwarding packets, which created a very nasty forwarding loop. Using some
VLAN other than #1 prevents such problems from impacting the boss node.
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