koitsu
Premium
join:2002-07-16
Mountain View, CA
| Odd SB5101 behaviour (broken firmware?)
I've managed to come across what seems to be some pretty major flaws with the SB5101, which all appear to be firmware related. Here's my list of things I've encountered:
* When something happens upstream (maybe Comcast is messing with something on the other end of the cable connection, as I never lose sync and all 4 LEDs stay solid), the modem simply stops working. It requires a hard power-cycle before the connection will start working again.
* During the above incident, the administrative page accessed via »192.168.100.1/ does not work; the modem appears to have shut off its own LAN interface in some bizarre manner; for a moment I thought it might be DHCP-related (re: fetching an IP from Comcast), but that shouldn't affect my ability to reach its administrative interface via Ethernet.
* The "Log" in the administrative page becomes full and stops updating -- even after a power-cycle. This limits my ability to see why/how some of the above situations may have occured. The only way to clear/empty the log is to use "Reset to factory defaults", then restart the modem via the web interface.
In regards to the first issue: no, my signal levels are fine (I just had Comcast out here to fix that -- and they look fantastic now).
What I find strange is that people here have voted the SB5100 series to be the most stable/reliable of all the modems out there... yet these bugs I've mentioned above are severe enough that I personally can't recommend this modem.
Are there alternatives to this modem? I presently rent it from Comcast; I have no problem with buying my own, but these sorts-of flaws are things I want to stay away from.
Looking for tips, advice, etc... thanks everyone. 
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| One thing I should clear up:
This does NOT appear to be DHCP-related (i.e. IP connectivity dying off due to a DHCP lease).
My router's DHCP client logs state the following:
Jan 14 19:23:23 gw udhcpc[83]: Lease of 67.161.37.216 obtained, lease time 232872
Jan 16 03:44:35 gw udhcpc[124]: Lease of 67.161.37.216 obtained, lease time 345600
Jan 18 03:45:30 gw udhcpc[124]: Lease of 67.161.37.216 obtained, lease time 345600
Jan 20 03:46:22 gw udhcpc[124]: Lease of 67.161.37.216 obtained, lease time 345600
Jan 22 03:47:10 gw udhcpc[124]: Lease of 67.161.37.216 obtained, lease time 345600
Jan 24 03:47:56 gw udhcpc[124]: Lease of 67.161.37.216 obtained, lease time 345600
Jan 25 16:10:36 gw udhcpc[29150]: Lease of 67.161.37.216 obtained, lease time 214641
Jan 25 16:10:43 gw udhcpc[29279]: Lease of 67.161.37.216 obtained, lease time 214633
Jan 25 16:13:02 gw udhcpc[29567]: Lease of 67.161.37.216 obtained, lease time 214495
Jan 26 22:01:01 gw udhcpc[29604]: Lease of 67.161.37.216 obtained, lease time 345600
Of course, I have no explanation for why the leases are expiring every 48 hours (2 days) instead of every 96 hours (4 days) like they should be; 345600 seconds = 5760 minutes = 96 hours = 4 days. This is something I'll have to look into myself (the router I use is a WRT54GL, so it's open-source and I'm decently familiar with the udhcpc code).
However, the issue I mentioned (see item #1) happened about 30 minutes ago; if it had happened at 22:00 or so tonight, then I could definitely say it's a DHCP-related thing -- but facts say otherwise.
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moot9
Premium
join:2005-12-23
Pompano Beach, FL
| reply to koitsu
I can't comment on other SB51xx modems... only the SB5100... it is rock solid... ConCrap is the one screwing the modem up... they are bouncing IP addresses... look at the class A you are getting/not getting...
Once they start changing the WAN IP, gateway, and DNS it just confuses the heck out of your system... no matter what OS you are using... the routing hops suck... |
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| said by moot9  :I can't comment on other SB51xx modems... only the SB5100... it is rock solid... ConCrap is the one screwing the modem up... they are bouncing IP addresses... look at the class A you are getting/not getting... Once they start changing the WAN IP, gateway, and DNS it just confuses the heck out of your system... no matter what OS you are using... the routing hops suck... That makes perfect sense -- except I appear to be getting the same WAN IP every time (no, I do not pay for a static IP). I haven't checked gateway changes though, but I'd expect it to remain the same (since my IP doesn't change).
None of that should affect the ability to visit »192.168.100.1/ though. Hell, even if the coax isn't connected I should be able to visit that IP to find out what the state of the cable modem is.
I wonder if there's other brands/models out there (maybe the SB5120?) which are better written.
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Making life hard for others since 1977. In memory of 2005... |
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moot9
Premium
join:2005-12-23
Pompano Beach, FL
| said by koitsu :I appear to be getting the same WAN IP every time I also had the same IP until last Dec. That's when things really started going bad to worse.
One thing I found that seemed to work to get to the modem was to release the IP, flush DNS, and renew the IP.
It seemed to work best using IPCONFIG commands... |
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koitsu
Premium
join:2002-07-16
Mountain View, CA
2 edits | Sorry if I come off crass, but this happened at 02:35 this morning, and I'm quite pissed off about it. Basically for 6.5 hours I had a cable modem which was synced up but had ZERO IP CONNECTIVITY what-so-ever.
You're not understanding the nature of the problem.
I cannot fetch an IP from Comcast until I power-cycle the modem. I cannot access the administrative panel until I power-cycle the modem. All four LEDs are lit and solid, meaning the problem is NOT with the cable/coax side of things, and there is nothing in the modem log after I power-cycle it.
I don't care if Comcast is doing maintenance on something upstream -- that's cool. However, I SHOULD NOT HAVE TO POWER-CYCLE MY EQUIPMENT FOR IP CONNECTIVITY TO BE RESTORED. Again, DHCP _DOES NOT WORK_ until I physically power-cycle the modem.
The only explanation I have is that there is some sort-of Layer 2 negotiation that is done *ONLY* when the cable modem is power-cycled, such as a MAC address being stored somewhere in Comcast's equipment. Someone clearing the ARP cache on a router could do this -- however, I SHOULD NOT HAVE TO POWER-CYCLE MY MODEM for the MAC address to be re-inserted into the ARP table.
It's also possible that something inside of the cable modem is being cleared/timing out (that isn't shown in the log) and is not restored until I power-cycle the modem. This would also be considered a bug of sorts.
This issue right here is severe enough that I am considering cancelling my service. This isn't a threat/whine, it's a fact. If my service goes out due to some tech. doing maintenance on the IP network, that's cool -- but I WILL NOT power-cycle my modem multiple times a day because of this. This is either a flaw in the SB5101 firmware, or Comcast themselves is doing something incorrect during whatever maintenances they're doing (regardless of time of day).
I'm likely going to have to call up Comcast's support line and start a battle with their Tier 1 folks to get me to communicate with T3 or so. This REALLY pisses me off.
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Johkal
Cool Cat
Premium,MVM
join:2002-11-13
Happy Valley
clubs: | What firmware version is it? |
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koitsu
Premium
join:2002-07-16
Mountain View, CA | reply to koitsu
Appears to be:
Software Version: SB5101-2.4.1.1-SCM14-NOSH |
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Johkal
Cool Cat
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join:2002-11-13
Happy Valley
clubs:
 ·Comcast Digital Vo..
 ·Comcast
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| That is a problematic version known for lock-ups. You need an update. If they won't update it, swap it.
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| reply to koitsu
Called my local Comcast office, who set up a ticket for the matter and said that if maintenance of any kind is being performed that usually the techs do not inform them ahead of time (I'm used to this, so no biggie).
The rep. scheduled a truck roll for tomorrow (01/30) between 0800-1000.
I'm not sure how a tech *coming out here* is going to help, other than to replace my SB5101 (could be faulty for all I know), or swap it out for another brand (seems unlikely since the SB5101 is highly respected around here).
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Making life hard for others since 1977. In memory of 2005... |
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| reply to Johkal
said by Johkal :That is a problematic version known for lock-ups. You need an update. If they won't update it, swap it. AWESOME. That is exactly what I wanted to hear.
As far as getting someone to upgrade it (which can be done remotely, from what I understand) -- how exactly do I get Comcast to do that? Will their support reps be able to do it, or does it require a field tech?
P.S. -- Johkal, you're my hero. Every question I've had you've answered. 
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Johkal
Cool Cat
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join:2002-11-13
Happy Valley
clubs:
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2 edits | reply to koitsu
You may have other issues, but I can tell you that the firmware is causing the issues as described.
Read through this: »SB5101 Research
Edit: the office can push the update. The tech coming out can call in and have it done while he is there also.
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| Thanks. I read the thread thoroughly -- very informative. Thank you for going on such a quest for information! It's people like you who make my (inquisitive) life easier.
It seems I'll have to be persistent with the Comcast reps and get them to push out a firmware upgrade, or otherwise wait for the field tech. to come out and do it.
Looks like I'll be pushing for SB5101-2.4.1.6-SCM02-NOSH or SB5101-2.4.1.5-SCM01-NOSH.
Funny reading stuff from DerEngel -- I'm somewhat familiar with the VxWorks base myself. I work on firmwares used in the Linksys WRT54G/GS/GL series, but not professionally.
For what it's worth in comparison (apples vs. oranges somewhat), there has been a long-standing problem with the Linksys WRT54G v5 units (which use VxWorks, compared to the older models which use Linux) randomly locking up (IP stack related problems, and probably resource exhaustion). Linksys has feverishly been trying to get the firmwares upgraded for the WRT54G v5.
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Johkal
Cool Cat
Premium,MVM
join:2002-11-13
Happy Valley
clubs: | I believe Comcast is pushing SB5101-2.4.1.5-SCM01-NOSH. |
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| said by Johkal :I believe Comcast is pushing SB5101-2.4.1.5-SCM01-NOSH. Sadly, no luck. I spoke to three different local Comcast reps, and got three different levels of service (generally speaking).
The first rep. was quick on the draw to tell me that they don't do firmware upgrades *at all*.
The second rep. in no way shape or form understood what I was telling them. Conversation, near-exact: "No, I need the firmware on the cable modem upgraded" "Hmm, you mean the IP address..." "No, I mean the code that the cable modem uses to work" "Hmm, right, so you mean the IP address" "NO, I mean the actual code on the cable modem; it's referred to as firmware" "Ohh, you mean the MAC address?" "..."
The third rep. definitely knew what I was talking about, and also took a moment to check out my signal levels. My downstream power level + SNR are perfect, but my upstream power level is starting to creep back up there (it's ~51dB at this point, which is higher than it was a few days ago). He was likely concerned with drop-outs, which I explained weren't the problem and that I hadn't had frame loss since a tech came out last week.
He then went off and put me on hold a couple times, and eventually came back to tell me that they in that specific office don't have the capability to do the upgrades directly, but that they *can* send off a request to another group (what he called the "database group") to have a firmware pushed to the modem. He said if that didn't happen within the next 24 hours, to simply have the field tech. do it when he comes out tomorrow.
Rather than continue to nag the Comcast support folk, I figure I'll just wait until tomorrow. For now, I've switched back over to my SBC DSL connection, at least until tomorrow.
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Johkal
Cool Cat
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join:2002-11-13
Happy Valley
clubs:
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1 edit | Hopefully they will update you or swap the modem. Even if they swap the 5101 for another 5101 with the same firmware version, it may have no issues. I in fact had that version with no issues. Some do, some don't. At the worst, you can always go buy a Linksys BEFCMU10 v4 modem which will not have an issue & will work fantastically.
While waiting to see if you get updated, reboot your modem every couple of ours and check your log entries.
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NormanS
Premium,MVM
join:2001-02-14
San Jose, CA
 ·Pacific Bell - SBC
| reply to moot9
said by moot9 :s... look at the class A you are getting/not getting... Does Comcast even have any Class A networks? Everything these days uses Classless Inter Domain Routing (CIDR). E.g.:
quote:
NetRange: 24.118.0.0 - 24.118.255.255
CIDR: 24.118.0.0/16
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Norman
~Oh Lord, why have you come
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koitsu
Premium
join:2002-07-16
Mountain View, CA
| reply to Johkal
said by Johkal :Hopefully they will update you or swap the modem. Even if they swap the 5101 for another 5101 with the same firmware version, it may have no issues. I in fact had that version with no issues. Some do, some don't. At the worst, you can always go buy a Linksys BEFCMU10 v4 modem which will not have an issue & will work fantastically. I reviewed the User Guide for the BEFCMU10, and I found no mention of an administrative interface (via HTTP or telnet or any other means). Do you happen to know if there's such an interface on these units?
While waiting to see if you get updated, reboot your modem every couple of ours and check your log entries.
I'm presently using my SBC DSL connection (need something reliable at least until tomorrow when the tech visits); in the meantime, I've hooked up the cable modem to my LAN segment (which is 192.168.0.0/16) so that I'm able to keep an eye on the cable modem without actually having to utilise its Internet connectivity.
So far it doesn't look like Comcast has done anything with it; still the same version. I went ahead and reset it to factory defaults (to clear the log), just in case.
Something tells me they're just going to let the field tech deal with it tomorrow... Oh well, patience is virtue (or so they say).
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Nerdtalker
Working Hard, Or Hardly Working?
Premium,MVM
join:2003-02-18
Tucson, AZ
clubs:
| said by koitsu :I reviewed the User Guide for the BEFCMU10, and I found no mention of an administrative interface (via HTTP or telnet or any other means). Do you happen to know if there's such an interface on these units? I've got a BEFCMU10 v4, and the web-interface actually beats the SB5100's in terms of the amount and detail of information provided, namely the inclusion of provisioned rates and modulation information.
Attached is a screenshot so you can judge for yourself. 
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moot9
Premium
join:2005-12-23
Pompano Beach, FL
2 edits | reply to NormanS
said by NormanS :Does Comcast even have any Class A networks? Everything these days uses Classless Inter Domain Routing (CIDR). E.g.: quote:
NetRange: 24.118.0.0 - 24.118.255.255
CIDR: 24.118.0.0/16
Ok, sorry, I stand corrected... I'll just say Comcast is bouncing hosts around different IP Addresses. Even assigning WAN, Gateway, and DNS addresses across networks... and I don't think that is good...
Anyway, here is the modem I'm using. I purchased it at Bestbuy in August '04.
Software Version: SB5100-2.3.2.5-SCM01-NOSH
Hardware Version: 3
MIB Version: II
GUI Version: 1.0
VxWorks Version: 5.4
The only thing I don't like is that it does not appear to generate it's own log entries consistently, i.e., ranging timeouts, connectivity loss with CMTS/plant, etc... sometimes there are entries, sometimes not... |
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