Re: Wake on LAN in the enterprise
WOL is unfortunately terribly deficient in that the spec. never envisioned the possibility of a need for wake on WAN. Bottom line, it's a non-routeable layer 2 protocol. Your choices boil down to the helper address nightmare you describe or proxy servers on every subnet. Owen On Dec 13, 2010, at 8:08 AM, Berry Mobley wrote:
Hello...
I'm trying to get a handle on implementation of wake-on-lan in an enterprise environment. Cisco gear, lots of subnets. I've made it work with directed broadcasts, but I'd really rather not have 40 or 50 'ip helper-address x.x.x.bcastaddr' statements on the vlans with the SMS servers.
Are there any enterprises that are doing this for large (100+) numbers of subnets? I can't find a single example anywhere with more than 2 networks.
I've searched the Cisco-NSP archives as well with no luck, but maybe I didn't go back far enough.
Thanks for any help you can provide.
Berry Mobley
On 12/13/2010 10:20 AM, Owen DeLong wrote:
WOL is unfortunately terribly deficient in that the spec. never envisioned the possibility of a need for wake on WAN.
Bottom line, it's a non-routeable layer 2 protocol. Your choices boil down to the helper address nightmare you describe or proxy servers on every subnet.
I would suspect that proxy servers being the better deal, though my experience with Cisco is that you may have to use ASR type gear to get a nicer layout (similar to service providers) where you can backend everything to a radius server (I'm still waiting to test this myself, but IOS is really weak on DHCP support). Jack
On 12/13/10 8:32 AM, Jack Bates wrote:
On 12/13/2010 10:20 AM, Owen DeLong wrote:
WOL is unfortunately terribly deficient in that the spec. never envisioned the possibility of a need for wake on WAN.
Bottom line, it's a non-routeable layer 2 protocol. Your choices boil down to the helper address nightmare you describe or proxy servers on every subnet.
I would suspect that proxy servers being the better deal, though my experience with Cisco is that you may have to use ASR type gear to get a nicer layout (similar to service providers) where you can backend everything to a radius server (I'm still waiting to test this myself, but IOS is really weak on DHCP support).
assuming you don't mind burning an ip address per subnet you can do this with a static arp entry for an ethernet multicast address even if your l3 platform doesn't allow subnet directed multicast. on a firewall platform basied on linux I specifically worked around the deliberate lack of subnet directed broadcast by natting from the broadcast address of the target subnet to an rfc 1918 address on the subnet with a static arp entry pointing at a multicast address. it worked fine, exploited the fact that rewrite occurs before forwarding on linux and allowed the use of a pre-existing management tool that used subnet directed broadcasts.
Jack
On Monday, December 13, 2010 11:20:20 am Owen DeLong wrote:
WOL is unfortunately terribly deficient in that the spec. never envisioned the possibility of a need for wake on WAN.
Use case I can think of: 'green' data center running VMware VI3 or vSphere with DRS and dynamically bringing blades online through WoL to handle load peaks and still stay green (when a host is empty, using the VMware API you can take it to maintenance mode and shut it down; use WoL to boot it back up when you need it).
Bottom line, it's a non-routeable layer 2 protocol. Your choices boil down to the helper address nightmare you describe or proxy servers on every subnet.
In the use case I mention it wouldn't be a problem, since under VMware DRS (which relies on VMotion) you have to have layer 2 transparency anyway. Would this not be a use case also for something like VPLS or EoMPLS?
participants (4)
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Jack Bates -
Joel Jaeggli -
Lamar Owen -
Owen DeLong