Cisco: limit number of DHCP addresses per VC?

Jesper Skriver jesper at skriver.dk
Sat Feb 7 22:53:26 UTC 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

01:01:00:00:01:02:03:04:40:02:01:20
^^^^^^^^^^^ ^^^^^^^^^^^ ^^ ^^ ^^^^^
  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
1.2.3.4

/Jesper

-- 
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.



More information about the NANOG mailing list