subnet broadcast across vlans

[Camelhump]

problem -

IT installed new switches - and at the same time implemented seperate vLans for each floor of our building.

each vLan has its own subnet.

 

now the retrospect server (G4/450 750m RAM, FW Raid5 1TB, backup to file, v6, OSX 10.3.9) can not see *any* client that is on a different floor.

 

Clients are a mix of PCs (98, 2000, XP) and Macs (os9 and OSX)

 

I have tried subnet broadcast - to the subnets on each floor - no effect.

 

I have seen a few references that it may be that Retrospect will not subnet brodcast across vlans.

 

 

any help, ideas, or confirmations appreciated

 

Thanks!

[natew]

Hi

 

The problem is the switches, not Retrospect.

As a test try connecting via direct IP address. That will probably work.

 

The IT people need to set up the switches to forward subnet broadcasts or multicast.

 

Thanks

nate

[Camelhump]

Thanks

[Camelhump]

NateW:

I copied and pasted your reply into an email to the network admin here> here is his reply:

</start>

This will never, ever happen on our network. Actually, that is very

irresponsible of them to suggest that as a fix.

 

A switch forwards broadcasts and multicasts out every port on the

particular vlan it is bound for. To suggest that subnet broadcasts and

multicasts be forwarded everywhere would turn the switch into a VERY

FAST shared hub. That would slow the network down considerably.

 

What they need to do is figure out why their software can't send a

unicast between workstation and backup device.

</end>

so....

what about unicast - what eve that is.....

 

thanks

[waltr]

hi camel,

 

 

 

Quote:

---

What they need to do is figure out why their software can't send a

 

unicast between workstation and backup device.

 

---

 

 

 

Retrospect does Unicasting. You just need to add each client by IP address:

 

 

 

http://72.14.203.104/search?q=cache:EiSbbGFZZ9kJ:www.mpulsetech.com/prod/ToUcastOrMcast.pdf+unicast&hl=en&gl=us&ct=clnk&cd=13

 

 

 

Quote:

---

Unicasting is communication between one sender and one receiver while multicasting involves sending data from one sender to multiple receivers.

In unicasting, the IP and port of the recipient is needed to uniquely identify the recipient.

In multicasting, a multicast group is given a class D IP address to which an interested recipient may join and listen to data that’s published on that multicast group. IP multicasting is achievedwith the help of routers that make copies as needed and deliver it to interested recipients.

 

---

 

 

 

your admin is telling you that he will not allow you to do Multicast or Subnet Broadcast across his new vlans. you'll have to get him to give you static IP's so you can do Unicast. Unicast won't work unless the IP is known and static.

[Camelhump]

Waltr:

Thanks for the info on "*casting".

 

however - this same network admin is also balking at giving me fixed IPs - he wants to use DHCP (3 day renewal cycle).

 

So....

where does this leave me???

 

up a creek?

 

buying Bru?

 

I *know* that this could have been resolved if this admin would have setup a single vLan for our department rather than by geographically (separate floors).

 

Thanks again

[waltr]

hi camel,

 

your admin has put you in a bad position. your question is more about office politics than anything. i can tell from the email that he sent you that he's very condescending, and not respectful of your position at all.

 

you mention Bru, but i don't understand the comment. how does Bru handle clients? if Bru needs multicast you will be in the same position after having spent good money, plus you'll look bad. weigh your options carefully before you make a decision here.

 

if it were me, i might take his email (and this thread) and go talk to the guys boss.

[awnews]

One other option--still use DHCP but set up a "reservation" or "static DHCP" assignment (fixed MAC=>fixed IP) so that the client PCs always get the same IP address. This will provide many of the same benefits as regular DHCP but will let you use Retro=>fixed IPs. New machines not assigned to this setup would still get assigned some of the othewise unassigned IPs.

 

It is some work to set up (have to find and enter a bunch of MACs & IPs), which your admin won't like doing...

[Camelhump]

waltr:

going to his boss might work - but somehow I doubt it......

 

GoAWest:

that is what has been done in my department (DHCP serving static) for the last 6 or so years.

but now he is balking at continuing this....

 

everyone:

thanks for your help

any other ideas I more than willing to listen.

[SimonHobson]

Quote:

---

NateW:

I copied and pasted your reply into an email to the network admin here> here is his reply:

</start>

This will never, ever happen on our network. Actually, that is very

irresponsible of them to suggest that as a fix.

 

A switch forwards broadcasts and multicasts out every port on the

particular vlan it is bound for. To suggest that subnet broadcasts and

multicasts be forwarded everywhere would turn the switch into a VERY

FAST shared hub. That would slow the network down considerably.

 

What they need to do is figure out why their software can't send a

unicast between workstation and backup device.

</end>

so....

what about unicast - what eve that is.....

 

thanks

 

---

 

Probably too late for you - I've just come across this whilst looking for an answer for someone else.

 

Turn round and ask him why he doesn't understand basic networking concepts !

 

Broadcasts happen ALL the time on any IP network, and in fact the network would not work at all without broadcasts or a LOT of administrator setup - Windows networking wouldn't work, and neither would Mac networking. Allowing directed broadcasts does not turn the switch into a hub, it merely allows a broadcast packet for the subnet to be sent from a remote machine, not just from a machine directly connected to the subnet. It will not in any way alter the traffic patterns within the subnet other than allowing these broadcasts. Retrospect only uses broadcasts and multicats to find the clients - once it knows where the clients are it then uses unicast to talk to it and perform backups.

 

He will probably still not want to allow this, so give him a pitying look, and ask him if he needs ACLs explaining ? ACLs are access control lists, and can be used to restrict traffic so that, for example, you can allow packets to the subnet broadcast address to only pass if they originate from your backup server and not from any other address. By doing this the network guy can allow your Retrospect to find it's clients with absolutely ZERO other effects on the subnets concerned - otherr than the traffic from the backup that is.

 

The way to tackle the boss is to ask why the network administrator is unable to correctly configure the network - because at the moment it is broken.