marcw
join:2001-05-18
Saint Paul, MN | modem alternatives Does anyone know of any modem that would work with Qwest AND be able to do half-bridging? And yes, I realize that it might not be supported by Qwest...
Some searching turned up a Zoom X3 but I'd like to know what other choices exist. Thanks! |
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| What do you mean by "half-bridging"? Generally, the type of you connection, e.g. PPPoA, PPPoE, or bridging/routing over ATM is determined by the ISP you use. |
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marcw
join:2001-05-18
Saint Paul, MN | Thanks, I am aware of that.
Half bridging, aka DHCP spoofing, allows the modem to authenticate *and* to pass the real IP addr on to one connected machine.
It seems to be quite popular in the UK and Oz but not all that much here which is why I'm looking. |
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| reply to marcw
I set my actiontec 1524 up in transparent briged mode and used raspppoe to connect and get an ip. I now have my router doing the pppoe authentication because the actiontech routing is crap. Pppoe is unsupported by qwest but I have seen a few other people that it works for. |
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marcw
join:2001-05-18
Saint Paul, MN | I couldn't get bridging to work. It simply would not authenticate. Several posts here and a call to Qwest seem to indicate that there are going to be Qwest customers who cannot get PPPoE (me, for example) and will find it impossible to do bridging.
The more I read about half bridging the more I think that this might be the ticket. The Zoom I mentioned earlier seems to have all the specs I'm looking for.
But I'd still be interested to know if there are other brands out there (available in the U.S.) besides Zoom that will do half-bridging and PPPoA. |
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3 edits | reply to jrustad
Im having trouble with my ZOOM X5 PPPoA it wont get 1500 MTU
Half bridge works great. |
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| reply to marcw
I wasn't familiar with half-bridging. From a quick study I would think it's not going to work unless the ISP is bridging. |
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marcw
join:2001-05-18
Saint Paul, MN | said by bigjoesmith:
I wasn't familiar with half-bridging. From a quick study I would think it's not going to work unless the ISP is bridging.
Hmmm... I didn't gather that in my reading. Please tell me where you found your info. Thanks! |
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marcw
join:2001-05-18
Saint Paul, MN | reply to wingman99
said by wingman99:
Im having trouble with my ZOOM X5 PPPoA it wont get 1500 MTU
Half bridge works great.
I wasn't aware that mtu was a function of the gateway. I thought it was only at the client. Or am I misunderstanding you?
Glad to hear half-bridging works for you. I believe I'll be trying out a Zoom X4 soon.
p.s. Your post looks much better now without that long rambling sig you had earlier... |
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Reviews:
 ·Future Nine Corp..
| reply to marcw
Check out »www.integral.com.br/images/2135.pdf, in particular Figure 1 and the description for Figure 1. The half bridging uses the PPP link to make the ISP router end of a serial link become an virtual ethernet node on the remote LAN. In other words the CPE and the PPP link effectively become a very long Ethernet patch cable, connecting the ISP router to the customer's LAN. In this figure there is a bridge on the client's end of the PPP link that can bridge ethernet over a PPP link. Likewise the other end of the PPP link (a Cisco router in this example) must be configured to participate in the half bridging.
The important observation is that the two ends of the PPP link must cooperate, using the PPP Bridging Control Protocol (BCP, RFC 1638) to make the link work as a super-long Ethernet patch cable. So to me, this implies that this is not something you can just configure on one end and make it work. Both ends have to be cooperating.
DHCP spoofing, (see »www.petri.co.il/configure_alcate···fing.htm) on the other hand, seems to be a different technology that might accomplish what you probably want...getting the real IP address available to your computer so you can have a direct connection to the Internet, not hampered by a NAT router. |
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marcw
join:2001-05-18
Saint Paul, MN | said by bigjoesmith:
Check out »www.integral.com.br/images/2135.pdf, in particular Figure 1 and the description for Figure 1. The half bridging uses the PPP link to make the ISP router end of a serial link become an virtual ethernet node on the remote LAN. In other words the CPE and the PPP link effectively become a very long Ethernet patch cable, connecting the ISP router to the customer's LAN. In this figure there is a bridge on the client's end of the PPP link that can bridge ethernet over a PPP link. Likewise the other end of the PPP link (a Cisco router in this example) must be configured to participate in the half bridging.
.......
DHCP spoofing, (see »www.petri.co.il/configure_alcate···fing.htm) on the other hand, seems to be a different technology that might accomplish what you probably want...getting the real IP address available to your computer so you can have a direct connection to the Internet, not hampered by a NAT router.
With just a cursory reading of the Patton article, it looks like this is an apples/oranges situation. You'll notice that it is merely a PPP device. Indeed, it says in the specs that authentication is not required. Of course with PPPoA (Qwest's protocol) that is simply not true. Authentication is absolutely required. I believe that this is the crux of the situation. PPPoA seems to require termination (and authentication) at the CPE. Also, I'm not altogether certain that their "half-bridge" term is equal to the same term used by the DSL modem makers. There seems to be a disconnect between what I read there and what I read in 5-6 different modem tech sheets. Zoom, Web Machine, Aztech, DSE, and a couple others I can't recall all say pretty much the same thing about half-bridging.
Your second example I think might also be hampered by a semantics thing. First off, the article looks dated but I'm not sure. Secondly, the implication is that spoofing is simply turning off NAT. With the DHCP spoofing (usually called half bridging in the docs I read), NAT doesn't even enter into the equation. With the half bridging I've been reading about, the modem authenticates the PPPoA (since it *has* to be done there) and then passes the real IP address on to *just one* other machine. Therefore, I believe there is no NAT to turn off.
Also, it looks like at least one other poster to this thread has indeed had a little luck in getting half-bridging working in the Zoom. I'll hopefully be getting a Zoom soon myself and will report back. |
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Reviews:
·Future Nine Corp..
| reply to marcw
Yes, after a bit of further reading, I think DHCP spoofing is different from the common useage applied to the term half-bridging.
Half-bridging is a mechanism for making a PPP link into a logical Ethernet patch cable, just a really long one. If I understand the technology correctly, it requires coordination on both ends. I don't think it's exactly the same as DHCP spoofing, but related.
DHCP spoofing, on the other hand, appears to be a clever technique to get the public IP address past the PPP endpoint. It only requires capabilities and configuration on the client's side of things - there is no need for the ISP to be involved.
In a PPPoA link (such as is used by qwest.com), the modem has to the be the PPP endpoint (since your computer doesn't speak A). When DHCP spoofing, the modem will negotiate the PPP, including the IP address for the endpoint, as part of the LCP for the PPP link. After setting up the link the modem will essentially go into a pass-through mode (a logical bridge). Any packets coming over the PPP link are translated into an Ethernet packet and sent out over the LAN-side Ethernet port interface.
The computer (router, whatever) connected to the LAN-side of the modem will acquire an IP address by acting as a normal DHCP client. The modem will function as a DHCP server, serving up the IP negotiated during the PPP link setup. The computer will use the public IP address and will essentially have an Ethernet bridge (provided by the modem) to the PPP link. |
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Reviews:
·Future Nine Corp..
1 edit | reply to marcw
Yes, some of this is just terminology. Most of the DSL modem references I've read refer to "DHCP spoofing" and not "half bridging." Most of the references I've found for half bridging appear to be things like the Patton device. Which is the more prevelant terminology is beyond my capability to say.
But they do appear to be two different (albiet related) mechanisms (in other words I agree with your apples/oranges comment).
Fundamentally it would appear that the Patton half bridging comes down to a BCP protocol within a PPP link. The "DHCP spoofing" as described in the Alcatel document (or here »www.skidmark.net/Spoofing.htm) is a normal PPP link combined with a "jimmied" DHCP server and packet pass-through mode.
Good stuff.
[edit for typo] |
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| reply to marcw
I have toyed with the PPP half bridge in my Zoom X4.
When it works, it works seamlessly.
However, most home gateways tend to puke out with the default and non changeable DHCP lease time of 1 minute.
My AMIT/SMC7004BR clone gateway with the latest known firmware still can't handle the lease. WinXP doesn't mind it though.
This is not to say there are not gateways that can't work with the PPP half bridge.
The Linksys WRT54G is known to work with it, another is the USR 8020 VPN gateway.
Also, in the half bridge mode, the PPP connection is dependent on something actually renewing the lease.
If the lease is released or not renewed, the PPP connection drops.
But it does hold much promise for those that are not able to use PPPoE. |
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Reviews:
·Future Nine Corp..
| reply to marcw
said by marcw:
Your second example I think might also be hampered by a semantics thing. First off, the article looks dated but I'm not sure. Secondly, the implication is that spoofing is simply turning off NAT. With the DHCP spoofing (usually called half bridging in the docs I read), NAT doesn't even enter into the equation. With the half bridging I've been reading about, the modem authenticates the PPPoA (since it *has* to be done there) and then passes the real IP address on to *just one* other machine. Therefore, I believe there is no NAT to turn off.
We're not in disagreement here. DHCP spoofing does turn off the NAT (that's sort of the whole point), so, yes, you could say there is no NAT to turn off at that point (it's already off). There's no routing either. There's a PPP link, a packet pass-through (and transliteration into an Ethernet frame), and a "jimmed" DHCP server. The server is "jimmed" to serve up the IP address negotiated during the PPP link setup. I suspect the DHCP server is also "jimmed" to provide an IP address pool of size 1. If you hooked up a switch to the DHCP spoofing modem and connected two DHCP clients to the switch, then I suspect 1 client would get an address and the other would not be served...the address pool is exhausted. |
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Reviews:
·Future Nine Corp..
| reply to AllTheRuss
said by AllTheRuss:
However, most home gateways tend to puke out with the default and non changeable DHCP lease time of 1 minute.
That's odd that they choose to have the modem serve up 1 minute DHCP leases when in DHCP spoofing mode. |
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| said by bigjoesmith:
said by AllTheRuss:
However, most home gateways tend to puke out with the default and non changeable DHCP lease time of 1 minute.
That's odd that they choose to have the modem serve up 1 minute DHCP leases when in DHCP spoofing mode.
I hear ya there. I tried changing the DHCP lease where it can be changed, but it made no difference in half bridge mode. It is locked to 1 minute once the half bridge is enabled.
Too bad Conexant locked it in like that, rather than reading the DHCP settings in the config, a lot more home gateways would not have an issue in the half bridge IMO. |
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4 edits | reply to marcw
I had no problems with half bridge. except my port 80 was open i had to close on d-link
On my Cisco 678 i locked in my NAT with my IP and it worked for a long time till i reboot, Then DHCP problems.
you have to select PPPoA =1500 PPPoE=1492 MTU
1500 contains only send and receive info no wrapper your connection is verified at the dslam. the PPPoE verified at isp with your Ethernet connection. With PPPoA has more privacy also the raper takes up(room on the packet) to identify you when the packets are moving how much what size what time.
what that means if your ISP supports 1500mtu you need 1500mtu
if isp is running 1500 and your running 1492 pppoe= packet fragmentation= slower, 1492=smaller, smaller=less band with.
PPPoA from isp to your PPPoA= FASTEST DSL connection.
PPPoE from ISP to your PPPoE= 2 little slower No Fragmentation
PPPoA From ISP to your PPPoE= 3 SLOWEST Fragmentation |
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QwestSLC
join:2004-03-01
Salt Lake City, UT | reply to marcw
I just order the Standalone Dsl...
They will ship to my house everything
Which modem should I expect?
Thanks |
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marcw
join:2001-05-18
Saint Paul, MN | said by QwestSLC:
I just order the Standalone Dsl...
They will ship to my house everything
Which modem should I expect?
Thanks
1) This probably should have been a seperate thread since it looks like it has little to do with the discussion in this thread.
2) I think that the answer to your question will be dependant upon your ISP. My ISP is Qwest Broadband Basic and I received the Actiontec. |
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