DOCSIS and valid IP address
Sonny Leman - SP
Currently, the cable company used both DocSis cable modem
(new customer)and non DocSis compliant COM21 cable modem
(previously installed customer).
They are using private / dynamic IP address (10.x.x.x), w/ DHCP
for DocSis users and their official reason was:
DocSis cable modems doesn't support static valid IP address.
DocSis only supports private IP address.
I told them that I don't buy that argument, but I have
no reference to support my argument that DOCSIS should be
able to support static and valid IP address.
So, is it true that DocSis has such a limitation ?
Is there any reference I can use ?
thank you,
-sonny leman
s...@indo.net.id
James Knott
Rod Smith
Sonny Leman - SP <s...@indo.net.id> writes:
> Hi all,
>
> Currently, the cable company used both DocSis cable modem
> (new customer)and non DocSis compliant COM21 cable modem
> (previously installed customer).
>
> They are using private / dynamic IP address (10.x.x.x), w/ DHCP
> for DocSis users and their official reason was:
> DocSis cable modems doesn't support static valid IP address.
> DocSis only supports private IP address.
>
> I told them that I don't buy that argument, but I have
> no reference to support my argument that DOCSIS should be
> able to support static and valid IP address.
I don't have a reference on point #1, but as to point #2, they're
clearly blowing smoke. I had a DOCSIS cable modem on AT&T Road Runner
(I cancelled it recently because I'm moving, though), and it gave me IP
addresses somewhere in the 66.x.x.x range, IIRC. They were definitely
*NOT* in the 10.x.x.x range. One caveat, though: Many cable modems have
THEIR OWN IP addresses in the 10.x.x.x range. These are used to access
the modem itself, rather than the Internet.
--
Rod Smith, rods...@rodsbooks.com
http://www.rodsbooks.com
Author of books on Linux & multi-OS configuration
Jonathan
addresses, although they can be dynamically assigned an IP address that is
statically configured in the DHCP address table(this is what happens with
computer and modem IP's on @home).
Cable routers which use internet routable IP addresses only, such as the
CISCO UBR9xx series do support static assignments of IP addresses
assignements
and can be configured in the same way as any Cisco router(with some
additional options). The routers though have built in NAT based firewalls
and the computers behind them are then assigned local space addresses
(10.x.x.x or 192.168.x.x) based on the configuration of DHCP services within
the cable router.
DHCP services can be configured to assign any IP address to the cable modem
however there are two major advantages to assigning internal space IP
addresses to the cable modem.
First some background, cable modems do not operate in the like routers, they
pass data back and forth between two given points and encrypt and decrypt
data. Therefore in the same way as an analog telephone modem, the computer
does not need to communicate directly with the cable modem so they do not
have to be on the same subnet. The only reason they have IP addresses at all
is some that cable modems can be configured while remaining online, be
queried for information and report data back to the routers for diagnostic
purposes.
Reasons:
1. Internet IP addresses are in short supply and therefore need to be
conserved.
2. If a modem is configured with and internal IP address it can not be
attacked by a hacker on the internet, therefore assigning an internal space
IP address offers a measure of security from DDOS attacks and the like
without the need for a firewall to be built into the modem and the
consequential reduction in diagnostic abbilities with the modem.
I hope that this helps.
Jon
"Sonny Leman - SP" <s...@indo.net.id> wrote in message
news:3B456F9C...@indo.net.id...
Jonathan
posted but hey.
I assume when you talk about the 10.x.x.x IP address you are referring to
that of the modem not of the computer. I would expect your computer to have
an internet IP address which seems to be 202.159.47.6. If that is not your
IP address then they have a firewall protecting there network.This might be
the case if they are trying to discourage their users from hosting services
on their computers.
In my post I was referring to the IP address assigned to the modems not the
computer or network device behind the computer.
Jon
"Jonathan" <j.ricka...@home.com> wrote in message
news:ovk17.10581$mY2.7...@news1.busy1.on.home.com...
Valentín Guillén
>
> Is there any reference I can use ?
>
DOCSIS provides for either static or Dynamic addressing of consumer's
modems. I've had a DOCSIS compliant modem for 11 months now, and since
day one, my MSO/Cable operator has issued me a static IP address. It's
worked fine, and I recently purchased my own DOCSIS compliant Toshiba
modem. It's also been assigned a static IP address. Most of my
neighbors use DHCP-assigned addresses, but I requested a static one,
and Comcast had no problem with that. We all use DOCSIS compliant
modems in Albuquerque, and it doesn't matter what manufacturer made
them.
Of course, that doens't address any issues or limitations which cable
companies in India may have. I just checked on the Indo.net web site,
and I must tell you, I would be suspicious/leery about ANY company which
advertised "Windows NT-based Webhosting Services".
Windows? Sheesh, give me a break here!
Regards,
--
Valentín Guillén
http://www.thuntek.net/~vguillen
cable geek
The OSS, CMCI, CMTS, and RFI portions of the DOCSIS specification
clearly identify DHCP as the means for establishing either STATIC or
DYNAMIC ip assigned to the mac address of the cable modem.
Download the specs at http://www.cablemodem.com/specifications.html
cg
Sonny Leman - SP <s...@indo.net.id> wrote in message news:<3B456F9C...@indo.net.id>...
John
Many cable providers use Nortel's NetID to provision new modems, when you
provision a new modem it gets it's own ip addy (usually a 10.) and keeps it.
If what you are referring to is a 10. IP address to your network card and
not your cable modem, then they are blowing smoke there as well. Cable is
just the medain the data is sent over, DOCSIS is the specifications of how
it's sent. Neither your computer or the DHCP server need to have anything to
do with DOCSIS.
Sonny Leman - SP
Valentín Guillén wrote:
>
> DOCSIS provides for either static or Dynamic addressing of consumer's
> modems. I've had a DOCSIS compliant modem for 11 months now, and since
> day one, my MSO/Cable operator has issued me a static IP address. It's
> worked fine, and I recently purchased my own DOCSIS compliant Toshiba
> modem. It's also been assigned a static IP address. Most of my
> neighbors use DHCP-assigned addresses, but I requested a static one,
> and Comcast had no problem with that. We all use DOCSIS compliant
> modems in Albuquerque, and it doesn't matter what manufacturer made
> them.
>
> Of course, that doens't address any issues or limitations which cable
> companies in India may have. I just checked on the Indo.net web site,
> and I must tell you, I would be suspicious/leery about ANY company which
> advertised "Windows NT-based Webhosting Services".
>
> Windows? Sheesh, give me a break here!
Actually, for my office, we use two ISP
- indo.net.id for dial up (we've been using this for over 5 years)
- link.net.id for cable modem (just for the last 1 year).
one of the reason we still maintain indo.net.id is that
LinkNet (http://www.link.net.id) are so stupid, that
they don't even know the USENET newsservers when I ask
a newsserver service.
I know, that Windows NT are not real network machine, but
that's the problem, more and more stupid people controlling
the net, at least here in Indonesia. I had a hardtime
promoting Un*x OS-es.
thanks for the info.
Sonny Leman - SP
On Fri, 06 Jul 2001 15:19:57 GMT, Jonathan wrote:
> I assume when you talk about the 10.x.x.x IP address you are referring to
> that of the modem not of the computer. I would expect your computer to have
> an internet IP address which seems to be 202.159.47.6. If that is not your
> IP address then they have a firewall protecting there network.This might be
> the case if they are trying to discourage their users from hosting services
> on their computers.
The IP 202.159.47.6 is from the other connection.
Let me tell the actual situation:
1] We have been using a dial-up connection with Linux+NAT
for internet connection in my office.
2] Later, we have a cable modem connection, with 13 actual/valid
IP address. But, i have to maintain my dial-up connection,
since the cable modem operator doesn't provide USENET news
server (they are so lame, that they didn't even know what
a news server is)
3] My office want to reduce cost, and goes for 1-2 IP address
only. They said, that in this case, the DOCSIS
technology doesn't support this (1 or 1 static & valid IP
address).
Now back to your statement:
> "Jonathan" <j.ricka...@home.com> wrote in message
> > It is certainly true that DOCSIS cable modems do not support static IP
> > addresses, although they can be dynamically assigned an IP address that is
> > statically configured in the DHCP address table(this is what happens with
> > computer and modem IP's on @home).
Well, if this is the case, then my ISP is partially correct.
Although, it's a kind of surprising for me.
Dynamic IP address might be the cracker's haven, it makes
it harder to pinpoint the criminals' addresses.
> > Reasons:
> > 1. Internet IP addresses are in short supply and therefore need to be
> > conserved.
i guess we need to push for the IPv6 deployment :-)
thanks for you info,
-sonny
Rod Smith
In article <3B49656F...@indo.net.id>,
Sonny Leman - SP <s...@indo.net.id> writes:
>
> Let me tell the actual situation:
> 1] We have been using a dial-up connection with Linux+NAT
> for internet connection in my office.
>
> 2] Later, we have a cable modem connection, with 13 actual/valid
> IP address.
This sounds like you've got a routeable network block of 16 static IP
addresses (16 minus 1 for the router minus 1 for broadcast minus 1 for
network equals 13 addresses).
> But, i have to maintain my dial-up connection,
> since the cable modem operator doesn't provide USENET news
> server (they are so lame, that they didn't even know what
> a news server is)
They might provide Usenet news, but the tech support person to whom you
spoke may have been clueless. Even if the ISP doesn't provide Usenet
news, there are various free and for-pay news providers out there, like
http://www.supernews.com, http://www.giganews.com, and
http://www.newsguy.com. (These are all pay outfits; I don't remember the
names of any of the free ones, offhand.)
> 3] My office want to reduce cost, and goes for 1-2 IP address
> only. They said, that in this case, the DOCSIS
> technology doesn't support this (1 or 1 static & valid IP
> address).
The problem with two addresses using your current model is that you
can't get a block of just two addresses AS A NETWORK BLOCK, which I
suspect is what you've got. This limitation has nothing to do with
DOCSIS; it's just that when you subtract the three addresses required
for a routeable network block, you'd have -1 addresses left. Doing it
this way for four addresses makes little sense because 75% of the
addresses are "wasted;" you're better off bridging the connection for a
single address. AFAIK, the smallest quantity you can get for a
routeable block is 8 (5 useable).
There are providers who use DOCSIS and who offfer two addresses, but
they're not handled via a router on the customer's premises; the router
is at the ISP.
My hunch is that your ISP offers two types of accounts: Static IP
addresses in fixed network blocks (possibly sold as business accounts)
and DHCP-assigned addresses singly or in small groups (possibly sold as
residential accounts). Both are handled via DOCSIS, if that's what
they're network uses. The limitation of using DHCP on the singleton
addresses is probably one of the ISP's policy, although I don't really
know enough about the guts of DOCSIS to say for sure that it can't
handle single IP addresses assigned statically. (Even if it couldn't,
DHCP can be configured to deliver the same IP address to any given
computer time after time.)
Sonny Leman - SP
Thanks for the info,
Rod Smith wrote:
> > 2] Later, we have a cable modem connection, with 13 actual/valid
> > IP address.
>
> This sounds like you've got a routeable network block of 16 static IP
> addresses (16 minus 1 for the router minus 1 for broadcast minus 1 for
> network equals 13 addresses).
May be for our current (lattest) setting.
Previously those 13 IP addresses are not contigous.
In the very beginning, before we got all 13 new addresses,
we have 1 IP, then add another, and another ==> 3 non contigous IP,
on the same COM21 modem, non DOCSIS compliant.
Later, the ISP gave 10 more addresses when we upgrade to new service.
After that, the ISP give a new block of 13 IPs.
> news, there are various free and for-pay news providers out there, like
> http://www.supernews.com, http://www.giganews.com, and
> http://www.newsguy.com. (These are all pay outfits; I don't remember the
> names of any of the free ones, offhand.)
This will be a possible alternative.
> they're network uses. The limitation of using DHCP on the singleton
> addresses is probably one of the ISP's policy, although I don't really
> know enough about the guts of DOCSIS to say for sure that it can't
> handle single IP addresses assigned statically. (Even if it couldn't,
> DHCP can be configured to deliver the same IP address to any given
> computer time after time.)
Well there is nothing I can do if they decide to gave us dynamic IP
address. On the other hand, having a number of servers co-located on
the ISP makes me notice that dynamic address tend to be the crackers
haven, it's hard to trace and finger pointing the bad guys since
the ISP simply doesn't have any record on who is using which IP.
(some ISPs have this kind of record on the _dial-up_ connection
since they need to keep track the usage).
thank you for your info,
-sonny leman