Option 82 & limit lease 1

Marc Perea marccp at srttel.com
Thu Mar 11 15:48:16 UTC 2010

Hi Terry,
we also map a specific public address to each individual port in an ISP environment. We've had no calls from subscribers who aren't able to get a DHCP assignment, but plenty of calls when we swap the customer modem since the lease is tied to the MAC address instead of the option 82 info. We get plenty of calls related to BRAS trouble, but that's fuel for a different list discussion.
What's the reason that you're finding no lease is available for a particular subscriber? I don't understand how that scenario is occurring and would like to help if I can, but in our environment as long as the same MAC asks for DHCP from the same location (agent.circuit-id), it always gets the same IP and we only see no free lease errors when a customer is trying to bridge to us instead of using our residential gateway. What is the situation that causes your need to worry about freeing the lease?
What I would worry about using option 1 is, let's consider that you did have a customer bridge and the first device grabs the IP for the circuit and ties its MAC to DHCP. Then, another device on the customer LAN asks for DHCP, and your scheme as outlined would turn off service from the server perspective for the first MAC by freeing the lease and potentially let the second device get the lease (depending on how you use omshell), at which point you'd have duplicate IPs on the customer equipment and an inconsistent lease.
In our scenario, we just deny any device beyond the first that asks for DHCP, so we should still get a call - at which point we tell the customer to install our RG and we run the clear lease process while the customer is on the phone and hooking it up correctly. Otherwise, at least one of the customer devices will work and we'll have a valid record of the lease for it.
Of your 3 ideas, I would definitely stick with option 1, but I am still curious what this process will "fix" for you? I get the impression that 2) won't work because of the way the server handles DISCOVER errors, and I agree that 3) is a poor choice.
I'm still getting to the 4.2 environment in our lab, but we have high hopes.
In your config, you are using spawn with option agent.remote-id. Is there any particular reason for doing so?
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