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Community Member

Wake On Lan Feature - How to enable??

Hi..

I would like to enable WoL feature in certain part of our network. Is there a global command to enable that?. or does it only require 'dot1x control-direction in' interface configuration?..

Also does the WoL Magic packet get forwarded through routers??

Any help appreciated.

Thanks.

GT

17 REPLIES

Re: Wake On Lan Feature - How to enable??

To forward the magic packet across a router, you will have to use an ip helper-address to the directed broadcast address of the target LAN. For example, if your client is on the LAN 192.168.42.0/24, then go to the LAN where the magic packet is being generated, and configure ip helper-address 192.168.42.255. On the target LAN, you will also need to configure ip directed-broadcast. You might want to put an access list on the directed broadcast for security, to allow only your management station to do the wakeup.

As for the dot1x stuff: I have never used that feature, so I shall leave it for someone else to answer.

Kevin Dorrell

Luxembourg

Community Member

Re: Wake On Lan Feature - How to enable??

Hi Kevin,

thanks for your reply. I might as well stay away from dot1x stuff.. have never used it but saw it on cisco site for WoL..

another question..

1. I'll have clients at multiple locations/ subnet.. so do I have to enter ip helper broadcast address for all those subnets?

2. If i have multiple routers between the server and client network, do I have to configure IP directed broadcast or ip-helper address on all these intermediate routers??

Thanks,

Hall of Fame Super Gold

Re: Wake On Lan Feature - How to enable??

Gibu

1) if you have clients at multiple locations/subnets then you will have to enter ip helper-address on each interface where there are clients.

2) you do not have to configure anything on intermediate routers. The intermediate routers just forward the traffic and do not need to know anything about it. You just need the helper-address on each interface where there are clients and the directed-broadcast on the interface where the WoL is being delivered.

HTH

Rick

Community Member

Hi All,

Hi All,

Very old post but hope someone will reply.From the below DOC

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91672-catl3-wol-vlans.html

" Because of the nature of the IP addressing architecture, only the last router in the chain, the one that is connected directly to the target subnet, can conclusively identify a directed broadcast. Directed broadcasts are occasionally used for legitimate purposes, but such use is not common outside the financial services industry."

If only the last router cares if it broacast, why we need to enable the helper address on the Source where the Management server is?

Thanks for your time.

Hall of Fame Super Gold

It is a very old post, but

It is a very old post, but here is your response. To implement WOL there are two functions which you must configure:

1) sending the magic packet from the server to the client which is configured on the vlan where the server is

2) receiving the magic packet which is configured on the LAN where the  client is.

Configuring ip directed-broadcast (which is what the link you posted is talking about) takes care of #2. Configuring ip helper-address takes care of #1. If you do not configure the helper address then the magic packet is never forwarded to the subnet where the client is located and WOL will not work.

HTH

Rick

Community Member

Hi Rick,

Hi Rick,

Many thanks for the fast reply.

Hall of Fame Super Gold

You are welcome. I am glad

You are welcome. I am glad that my answer was helpful.

HTH

Rick

Re: Wake On Lan Feature - How to enable??

Could I just clarify the answer that Rick gave? I fear that it might give the impression that the ip helper-address is on the remote LAN, which it is not.

You should put the ip helper-address on the LAN where you have the management server that is trying to wake up the remote PCs. If the remote PCs are distributed across several remote LANs, you will need one ip helper-address command on the "central" LAN for each and every remote LAN you are trying to get to. You can have as many ip helper-address commands as you need to cover the remote LANs you have.

As Rick says, if you have multiple routers between the server and clients, then the ip helper-address commands only need to be on the LAN that hosts your management server.

What the ip helper-address command does, is to recognise broadcasts on the server LAN, and convert them into unicasts to the address you specify: in my example 192.168.42.255. These unicasts are routed through the network in the normal way until they reach the destination LAN. When they get there, the client LAN's router say "eh-up, this is my IP subnet broadcast address; I had better put a broadcast MAC header on it." But it will only do that if you have configured ip directed-broadcast on the target LAN.

If you think of the way it works, you could even do WoL across the Internet, where you do not have the hand on the intermediate routers.

Is that OK?

Kevin Dorrell

Luxembourg

Hall of Fame Super Gold

Re: Wake On Lan Feature - How to enable??

Kevin

Welcome back - and thanks for the clarification. I was thinking it backwards.

HTH

Rick

Community Member

Re: Wake On Lan Feature - How to enable??

Thanks Guys.. i know what has to be done to make it work now.. will update once I configure it..

Thanks,

Community Member

Wake On Lan Feature - How to enable??

I realize this is an old post, but I'd like to ask a few questions if I may.

1.) Will this setup work if the packets are traversing an IPSec VPN tunnel?

2.) Should ip directed-broadcast ACL on the target router permit all IP or just UDP?

3.) The interfaces I'll be using are VLAN interfaces. Does that pose a problem?

4.) I think I understand the concepts here, but I need to clarify for myself:

    The ip helper-address commands (I'd need two) are configured on the source interface, correct?

Thanks for your time, sir.

Bryant C Mothershed

(Just and old cowboy that wound up in IT)

Hall of Fame Super Gold

Wake On Lan Feature - How to enable??

hashknife wrote:

I realize this is an old post, but I'd like to ask a few questions if I may.

1.) Will this setup work if the packets are traversing an IPSec VPN tunnel?

2.) Should ip directed-broadcast ACL on the target router permit all IP or just UDP?

3.) The interfaces I'll be using are VLAN interfaces. Does that pose a problem?

4.) I think I understand the concepts here, but I need to clarify for myself:

    The ip helper-address commands (I'd need two) are configured on the source interface, correct?

Thanks for your time, sir.

Bryant C Mothershed

(Just and old cowboy that wound up in IT)

1, yes

2 UDP

3 no

4 yes.

Community Member

Wake On Lan Feature - How to enable??

Thanks Paolo.

Wake On Lan Feature - How to enable??

One more point about #2: most WoL systems use the UDP discard port, UDP/9.  Start with allowing UDP to any port, and once it is working try restricting it to UDP port 9 only and see if it still works.

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