VLANS and DHCP

[Steve Wenger]

the dhcp-server-identifier is I think the address that is specified by the 
IP Helper in the cisco, my question is will that helper address direct the 
traffic to the proper section in the dhcpd.conf file?
Example if the ip-helper address is 206.126.242.2 will the traffic skip over 
the vlan 19 and goto vlan20?

#Vlan 19 - Rubicon Private
subnet 172.19.0.0 netmask 255.255.254.0 {
         range 172.19.0.10 172.20.0.254;
         option routers 172.19.0.1;
         option subnet-mask 255.255.254.0;
         option dhcp-server-identifier 172.19.0.2 }
}
#Vlan 20 - Rubicon Public
subnet 206.126.242.0 netmask 255.255.254.0 {
         range 206.126.242.5 206.126.243.254;
         option routers 206.126.212.1;
         option subnet-mask 255.255.254.0;
         option dhcp-server-identifier 206.126.242.2
}

Steve Wenger
Nconnect Internet and High Speed Wireless.
Got a need for speed?  We have a solution for you!


-----Original Message-----
From: Joseph Huang ¶À¥ß¦æ <lshuang at mcu.edu.tw>
To: dhcp-users at isc.org
Date: Fri, 18 Aug 2006 13:30:54 +0800
Subject: Re: VLANS and DHCP

> If your routers are cisco like
> just add "ip helper-address dhcp.server.ip.address" configuration in
> each vlan interface
> like:
> Switch>enable
> Switch#configure terminal
> Switch(config)#interface vlan 1968
> Switch(config-if)#ip helper-address 192.168.100.200
> Switch(config-if)#end
> 
> then the router will relay dhcp packets between dhcp server and dhcp
> client
> 
> if you want to use a dhcp server with many virtual interface to do this
> you need
> 1. a nic with 802.1q vlan support on your dhcp server
> 2. define virtual interfaces on your dhcp server machine
> 3. define a trunk port which directly connect to dhcp server's nic and
> brings all vlan tag to the nic of dhcp server
> cisco like config is :
> Switch>enable
> Switch#configure terminal
> Switch(config)#vtp mode transparent
> Switch(config)#interface gigabitEthernet 0/12
> Switch(config-if)#switchport trunk encapsulation dot1q
> Switch(config-if)#switchport mode trunk
> Switch(config-if)#end
> 
> 4. tell dhcp server to listen dhcp packets on virtual interfaces
> 
> however, maybe nic won't support more than 64 vlans
> so, i think you need both router's dhcp relay and dhcp server's virtual
> interface configuration
> (mix L2 and L3 traffic on the router or core switch)
> 
> finally, you can download cisco's "Multilayer Switch Software
> Configuration Guide" of their products
> on cisco's web site, their manual is really easy to understand.
> 
> good luck!
> 
> Joseph Huang
> 
> 
> Steve Wenger wrote:
> > I will be running it on Fedora Core 5,  I am going to have approx 100
> total 
> > vlans to start, and I know it can be done I am just not sure how to
> get it 
> > done.
> >
> > Steve Wenger
> > Nconnect Internet and High Speed Wireless.
> > Got a need for speed?  We have a solution for you!
> >
> >
> > -----Original Message-----
> > From: Michael Loftis <mloftis at wgops.com>
> > To: dhcp-users at isc.org
> > Date: Thu, 17 Aug 2006 20:27:59 -0600
> > Subject: Re: VLANS and DHCP
> >
> >   
> >> --On August 17, 2006 9:09:53 PM -0500 Steve Wenger 
> >> <steve at nconnectwireless.com> wrote:
> >>
> >>     
> >>> I am currently running a wireless network with over 2ooo clients
> >>>       
> >> attached
> >>     
> >>> to  50 different access points,  I will be reconfiguring the
> network
> >>>       
> >> and
> >>     
> >>> setting  up different VLANS for each tower location.  I want to use
> >>>       
> >> one
> >>     
> >>> centralized  DHCP server so I need to configure a DHCP server that
> >>>       
> >> can
> >>     
> >>> assign clients  addresses from multiple address blocks both public
> >>>       
> >> and
> >>     
> >>> private based upon  the VLAN that the client is part of.  Can
> anyone
> >>> point me to some  documentation on how to accomplish this.
> >>> Steve Wenger
> >>> Nconnect Internet and High Speed Wireless.
> >>> Got a need for speed?  We have a solution for you!
> >>>       
> >> What platform?  Linux and FreeBSD both support an 802.1q/VLAN
> >> encapsulation 
> >> driver.  I've used both to run DHCP and they work very well.  They
> both
> >> expose an interface to DHCPd, so there's nothing 'special' as far as
> >> DHCPd 
> >> is concerned.  In Linux there's an option you have to sometimes set
> >> that 
> >> makes sure the Layer2 Ethernet headers are correct in order to make
> >> certain 
> >> the DHCPd works.  In any case it's not the DHCPd that does the VLAN 
> >> interface, it's the host OS.
> >>
> >>     
> >
> >
> >
> >
> >   
> 
> 
>