 nitzguyPremium
join:2002-07-11
Sudbury, ON
 ·TekSavvy DSL
| reply to Teddy Boom
Re: [Cable] Trying to use a gigabit switch with DCM475 modem dir said by Teddy Boom:It was a great explanation nitzguy, but...
said by nitzguy:Cable modems hold onto that memory for some reason and when he reset the modem, it wiped that I believe resetting the modem causes Rogers DHCP server to release the old leases and start issuing new ones. I don't think anything about the public IP leases is actually stored in the modem. Of course I could be wrong, and I'm very interested in confirmation details either way! I'm sure that part of the spec hasn't changed since D1.0....and after taking about 50,000 support calls on the subject I'd still like to consider my explanation as the truth  .
Hence why we ran into an issue with an Asus motherboard...can't remember the version of it...but there was a bug in the Windows XP driver which would cause the MAC address to be set/imposed onto the NIC, so when the user tried to get online, we would see that MAC address bound to the modem in the diagnostics...and since you can't have duplicate MACs on any network segment...and since cable acts as 1 huge network segment...the DHCP server wouldn't give out an IP because since there's only 1 DHCP server, and it said "I"ve already given out an IP for this MAC address..."...it couldn't give out another one...
Why does the cable modem hold this information? I'm thinking for these sorts of purposes to only assign X number of IPs. But I can tell you that the modem acts as a pass-through for the public IPs...in reality it acts as a transparent DHCP relay...I don't know why this is the case, but I can tell you that the modem gets its own IP and that it records the MAC addresses of the devices that are trying to connect....because I'd usually know when someone had a router connected based on the MAC address and they'd try and tell me that wasn't the case .
I can tell you that the cable modem itself gets its own IP address that's separate from a public IP....the cable modem is a hell of a lot more complicated than an ADSL modem (don't really know how VDSL modems sync since I've never used one) in that regard and acts more like an interface device than a simple, give me sync and figure everything out yourself.
It is kinda silly to do it that way the OP is doing, but maybe there's a reason...maybe its just for ease of use sake...maybe he's got this switch lying around and doesn't want to spend money on another router as he has had some issues with routers in the past. |
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nfsc
join:2011-11-05
North York, ON Reviews:
 ·TekSavvy Cable
| the reason is i need a temporary solution before i go do something that will take some time and concentration off my exams. After my exams, i am planning on getting a new router, as a permanent fix. But i needed to connect all the computers in the house appropriately. My parents bug me when my computers are on the same network as theirs, since i tend to hog the connection. The Dlink DIR-655 QoS engine does something weird where when i try to torrent something, i get limited to 1mB/s, and the network is crippled...u can't browse the nets. Turning it off gives me 3.5mB/s easy, but still can't browse without waiting 5 minutes for google.ca to load XD. The switch is a great tool for sharing files between computers using Samba. sharing over wireless is horrendous :/ not going to explain my entire setup, but computer A uses computer B as a file storage server, hence i need the two computers to be on the same network.
Also, i'm having troubles choosing between the ASUS RT-N65U and the RT-N66U. one has usb 3.0, the other has dd-wrt support. Neither has both.
Another thing about asus is, they have great hardware, but they are lacking in the software department. From motherboard BIOS to drivers, to various firmware. More than half of my electronics are asus >.> i still have a Pentium II motherboard, in working condition from asus :| |
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| reply to Teddy Boom
said by Teddy Boom:It was a great explanation nitzguy, but...
said by nitzguy:Cable modems hold onto that memory for some reason and when he reset the modem, it wiped that I believe resetting the modem causes Rogers DHCP server to release the old leases and start issuing new ones. I don't think anything about the public IP leases is actually stored in the modem. Of course I could be wrong, and I'm very interested in confirmation details either way! nitzguy is correct, at least for the DCMxxx modems. Process works like this:
1. On startup, the modem clears all memory of connected MACs.
2. The modem gets a MAC limit from the ISP (actually probably some DOCSIS network component). For the RED area it is 2 MACs.
3. The modem stores the first two MACs it sees, and only allows those MACs to send traffic.
3.a. A restart will clear the MAC list under normal conditions. Worst case try a factory reset to reset the limit, though this is usually not necessary.
3.b. It is not possible to simply unplug one of the first two MACs and reconnect a third, as the third MAC is not on the modem's MAC list of two.
3.c. I'm unsure if the modem MAC list has a timeout. I suspect it does not, or if it does, it is very long.
3.d A switch will not be counted as an additional MAC, however a router will.
DHCP is entirely separate as far as I can tell. |
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 GuspazGuspazPremium,MVM
join:2001-11-05
Montreal, QC
kudos:19 | reply to nfsc
The cable modem isn't doing any QoS; maxing out the connection on one of the two computers should still kill the connection for the other. If this setup performs any better than a router with QoS disabled, then something is wrong with the router. On the subject of QoS, it can only be performed by a device that is routing traffic for all the computers, which the modem isn't.
The correct setup including your switch should be:
Cable modem ethernet port ---> router WAN port
router switch port --> gigabit switch port
computer ethernet ports --> gigabit switch ports
--
Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org |
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nitzguyPremium
join:2002-07-11
Sudbury, ON Reviews:
·TekSavvy DSL
| reply to nfsc
said by nfsc:Another thing about asus is, they have great hardware, but they are lacking in the software department. From motherboard BIOS to drivers, to various firmware. More than half of my electronics are asus >.> i still have a Pentium II motherboard, in working condition from asus :|
Rather than getting to your whole post...I can completely understand the need for 2 public IPs...and just speak to ASUS...they do make great hardware...its was a bug in the Windows XP driver from Microsoft and it was just in 1 model, that would auto-detect and install...the ironic thing is they needed the ASUS driver...and needed to go to the ASUS website so we'd have to go in and edit the properties and just spoof the mac....
Anywho...for the modems, all cable modems act pretty much the same way, I saw it on other types of modems not just RCA modems . |
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mlord
join:2006-11-05
Nepean, ON
kudos:8 Reviews:
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·TekSavvy Cable
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| reply to Guspaz
said by Guspaz:The cable modem isn't doing any QoS; maxing out the connection on one of the two computers should still kill the connection for the other. I don't see any reason for that to happen. Much more likely, is the modem will just treat the two connected MACs in something akin to a round-robin packet scheduling setup. So even with one MAC maxing out the connection, packets to/from the other MAC will likely not get held up.
Edit: QoS is mainly about managing packet queues. The modem itself probably has a very short queue, compared to the attached PCs with their GBytes of RAM. So the modem won't be buffering more than a few packets for either MAC, which effectively would allow it to prioritize the two equally with minimal latencies for either. In other words, a crude yet effective round-robin QoS. And I imagine the CMTS to be behaving similarly when scheduling packets for the downstream. |
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nitzguyPremium
join:2002-07-11
Sudbury, ON Reviews:
·TekSavvy DSL
| said by mlord:said by Guspaz:The cable modem isn't doing any QoS; maxing out the connection on one of the two computers should still kill the connection for the other. I don't see any reason for that to happen. Much more likely, is the modem will just treat the two connected MACs in something akin to a round-robin packet scheduling setup. So even with one MAC maxing out the connection, packets to/from the other MAC will likely not get held up. Edit: QoS is mainly about managing packet queues. The modem itself probably has a very short queue, compared to the attached PCs with their GBytes of RAM. So the modem won't be buffering more than a few packets for either MAC, which effectively would allow it to prioritize the two equally with minimal latencies for either. In other words, a crude yet effective round-robin QoS. And I imagine the CMTS to be behaving similarly when scheduling packets for the downstream. It uses TDMA from the Modem to the CMTS to slice the time up...much like how the old TDMA Cell phones worked.
From the computers through the switch they're using CSMA/CD, so I'm wondering if that's the issue here...is that so much traffic is being requested from Computer A, that Computer B has to "wait" forever?
So, definitely not QoS because it doesn't pick what kind of traffic to prioritize, but a FIFO system more than likely.... |
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mkay
join:2008-04-13
Kingston, ON | reply to Guspaz
cogeco has always allowed 3 ips methinks. i used to plug the usb cord into the cable modem and install the drivers to get internet on my laptop when i didn't have a router. |
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mlord
join:2006-11-05
Nepean, ON
kudos:8 Reviews:
·Start Communicat..
·TekSavvy Cable
·TekSavvy DSL
| reply to nitzguy
said by nitzguy:It uses TDMA from the Modem to the CMTS to slice the time up...much like how the old TDMA Cell phones worked. Not to mention more modern GSM phones there too. 
From the computers through the switch they're using CSMA/CD, so I'm wondering if that's the issue here. |
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nfsc
join:2011-11-05
North York, ON Reviews:
·TekSavvy Cable
| reply to Guspaz
said by Guspaz:The cable modem isn't doing any QoS; maxing out the connection on one of the two computers should still kill the connection for the other. did i forget to add, the Dlink DIR-655 is broadcasting my backup DSL connection through wireless now? if my parents use an entirely different internet connection than me, im pretty sure their computers will not be affected by mine 
also, the two ip's are good when i want to host a server of some sort (game server) the Dlink DIR-655 can't port forward for some magical reason XD. And the second ip can just go to a router. My main computer which turns into a server if i want to has 2 GbE ports. so i can connect one to router and one to switch later on. (if the router new router port forwards properly, i will ditch the switch) Thus i can make my main computer a public server whenever i so please. i do host temporary (maybe like 2 days every 3 months?) game servers for the occasional time me and my friends want to chill
also, after doing some research, i discovered USB 3.0 actually causes interference with wireless signal...so i will end up getting the Asus RT-N66U, as it provides everything i need.
i hope my posts aren't too disorganized...I see people are too lazy to read my entire posts...must be something i'm doing wrong  |
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