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Community Member

ip directed-broadcast and wake on lan

Hello, we are currently investigating using wake on lan capability for pushing patches & update to workstations during off hours.

The LAN environment consists of a core 6509 switch with a MSFC and fiber connections to 4006 floor switches. We use an addressing scheme of 172.18.0.0 / 24 so each floor switch is a subnet.

In order for wake on lan to work it needs to send a broadcast packet to all hosts on a subnet. Enabling ip directed-broadcasts on the vlan interfaces of the MSFC appers to allow the subnet broadcast

A few questions I have are:

1) would this have the effect of "flatening" the network into one big "segment" making it vulnerable to broadcast storms?

2) is there any function in the switch that can accomplish waking a mac on a port?

3) are there any other recommended alternatives

Thanks

4 REPLIES
Cisco Employee

Re: ip directed-broadcast and wake on lan

I cannot think of any other way to make Wake on LAN work. I have seen lot of customers implement it using "ip directed-broadcasts"

Community Member

Re: ip directed-broadcast and wake on lan

Well, conceivably, the problem could also be solved using multicast, as the 'magic packet' doesn't need to be an IP broadcast. (It can be any type of packet, even non-IP, containing the magic sequence).

However, I haven't actually seen any applications using anything but IP broadcast..

Some of my customers are actually putting a 'WOL proxy' on each and every VLAN to get WOL...

-A

Community Member

Re: ip directed-broadcast and wake on lan

thanks, if I understand the WOL proxy idea correctly... you would send a magic packet to a specific address on each vlan. That would eliminate the need to enable ip directed-broadcast on each vlan interface. But how would that machine forward the packet to all the other stations on its vlan?

Community Member

Re: ip directed-broadcast and wake on lan

I am puzzled.

1. What LAN card and what software customers are using to implement WOL ? magic packets are tcp/ip packets or its netbios ?

2. If there s a router in the middle, how would magic packets cross over to the other side ?

3. Apparently, the magic FRAME is directed to specific machine and has specific ethernet address or it can be broadcast address so all NICs respond ?

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