ntl DHCP changes

[jtwn]

Anybody noticed the difference?

[James Henry]

http://www.cisco.com/en/US/products/...08022eba7.html

Not really, what do you mean ?

[Neil]

Originally Posted by jtwn

Anybody noticed the difference?

Could you be a bit more vague please?

[jtwn]

The 'cust' part now doesn't appear to relate to your address anymore.

I wonder if you can still even force an IP change by changing a connected device's mac address.

---------- Post added at 12:22 ---------- Previous post was at 11:06 ----------

Originally Posted by James Henry

http://www.cisco.com/en/US/products/...08022eba7.html

Are you trying to say something? Thats why my new address doesn't have a cable number, or at least a positive one?

[Graham M]

Thats a DNS change more than a DHCP change then.

[rdhw]

Originally Posted by jtwn

The 'cust' part now doesn't appear to relate to your address anymore.

Yes the 'cust' part does still relate to your IP address, but not in the obvious way that previously applied. Previously, each customer-side interface to the CMTS (or uBR), as identified by card and cable number, had its own set of IP subnet ranges, each usually quite small, for instance with a netmask of 255.255.255.0. In that system, the custXXX element of the DNS name was identical to the final octet of the IP address.

In the new system, many interfaces on a single CMTS have been bundled together for the purposes of IP address allocation, resulting in fewer and larger IP subnets spanning several CMTS interfaces. A strong motivation to do this is to economise on the number of IPv4 addresses wasted and unusable when many small subnets are used. Better utilisation of the increasingly scarce IPv4 addresses can be achieved with fewer larger subnets.

For instance, my connection to Cambridge UBR 8 now has a netmask of 255.255.252.0, a subnet of size 1024 instead of the previous size of 256. The gateway address has become 82.6.104.1 (instead of being a .254 address). User IP addresses are available from 82.6.104.2 (DNS cust1) through to 82.6.107.254 (DNS cust1021). The correspondence between IP address and the DNS custXXX element is still there, if you do the sums.

[jtwn]

Ah right, I now understand, thankyou for your explanation.

The link you posted James Henry didn't register the first time round

[Chrysalis]

this might be what happened to me last week when my ip changed then. My current subnet is a 252.

[monkey2468]

Does this make it easier to reseg after the addition of new cards to the UBR?

[BBKing]

Thanks rdhw for a concise and full explanation as ever, that's precisely how it works

monkey2468 - yes, it means less work for the lads on the night, less to go wrong, fewer scopes on DHCP servers (which saves memory and increases capacity). The real driver, however, is private IP addresses, as you use them more efficiently and there's a finite number available.

The cust number is still related to your IP address, except that it's not obvious if you write the IP in human-readable dotted quad form! It works brilliantly in binary...

[monkey2468]

Originally Posted by BBKing

Thanks rdhw for a concise and full explanation as ever, that's precisely how it works

monkey2468 - yes, it means less work for the lads on the night, less to go wrong, fewer scopes on DHCP servers (which saves memory and increases capacity). The real driver, however, is private IP addresses, as you use them more efficiently and there's a finite number available.

The cust number is still related to your IP address, except that it's not obvious if you write the IP in human-readable dotted quad form! It works brilliantly in binary...

Doesn't everyone think in binary? (damn those inplants )