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Re: Cisco: limit number of DHCP addresses per VC?

  • From: Jesper Skriver
  • Date: Sat Feb 07 17:55:33 2004

On Wed, Feb 04, 2004 at 08:38:27AM -0600, Claydon, Tom wrote:
> Question for the list:
> Cisco introduced a command in 12.3T to limit DHCP leases on ATM unnumbered
> interfaces (ip dhcp limit lease per interface). This feature works fine on
> our 7206VXR, but my problem is that this is a global command. The Redback we
> were using before had us spoiled by allowing us to specify max DHCP leases
> per ATM VC! We would like to put other ATM VC's on this router that have
> different DHCP lease requirements.
> Is there any way of limiting DHCP leases per VC? Cisco TAC said they didn't
> have a non-global version of the ip dhcp limit lease per interface command.
> Our DHCP server is running dhcpd 2.0p15, BTW.

You can use the option 82 in the DHCP packet to do this on the DHCP
server, something like

# By default limit all customers to 1 DHCP lease
class "customer" {
	spawn with option agent.remote-id;
	lease limit 1;

subclass "customer" __OPTION_82_STRING_FOR_CUSTOMER__ {
	lease limit 2;

__OPTION_82_STRING_FOR_CUSTOMER__ will be something like

^^^^^^^^^^^ ^^^^^^^^^^^ ^^ ^^ ^^^^^
  fixed     NAS IP addr |  |   VCI
                        |  VPI
                  Port in this case 4/0

So this customer's pvc is 2/288 on ATM4/0 on the NAS with address


Jesper Skriver, jesper(at)skriver(dot)dk  -  CCIE #5456

One Unix to rule them all, One Resolver to find them,
One IP to bring them all and in the zone to bind them.