Who'd have thought the switch wouldn't pass multicast? Is it possible the
campus network geeks told it not to? Using multicast for disseminating data
like that "just makes sense".
Glad you found THAT problem. What brand of switch, anyway? Cisco?
gerry
On Tue, Mar 14, 2017 at 3:30 PM, Gilbert Sebenste <gilbert@xxxxxxx> wrote:
> Hello everyone,
>
>
>
> The College of DuPage has a NOAAport receiver with a Novra S300N, and two
> Ubuntu boxes as ingestors, so that if one fails, the other will still
> provide data. To accomplish this, they use an enterprise level network
> switch, a Nortel/Avaya 5520, that costs a lot of money (and not the $50
> gigabit switches you can get from Newegg, or wherever), to split the data
> feed so that both servers can get and ultimately relay the data.
>
>
>
> When trying to receive the test GOES-16 imagery months ago, it wasn’t
> coming across their NOAAport feed. I thought it was a glitch with their
> Novra box, or the network switch. But now that GOES-16 data is being sent,
> neither NOAAPort ingest server were getting the GOES-16 data on the NOTHER
> feed. What could be wrong?
>
> We restarted the LDM on both servers, deleting and remaking the queues.
> That didn’t do anything.
>
> We then double checked the ldmd.conf files, which had a few minor issues,
> and also checked the logs,
>
> of course. Still, no GOES-16 data was showing up.
>
> We then did a packet sniff from one of the servers to the switch. No
> GOES-16 test data was being sent to the boxes from the switch!
>
>
>
> We then made sure the Ubuntu kernel parameters were set correctly, per the
> LDM instructions. One box didn’t have it correct; the other was correct. We
> rebooted both boxes after doing checks. That didn’t get us GOES-16 data,
> either.
>
>
> So then, today, I convinced a College of DuPage meteorology program
> employee to go out to the bitter cold dish farm and climate-controlled “dog
> house” where the Novra and the servers are. As he power-cycled the Novra, I
> was doing an ldmadmin watch on the NOTHER feed on the ingest servers. When
> the Novra came back up after the power cycke…no GOES-16 data was coming
> across to the servers!
>
>
>
> So then we looked to the network switch. The employee grabbed a jumper
> cable, and ran an Ethernet cable directly from the Novra to one of the two
> ingest servers. Then, finally, GOES-16 data started pouring in on that
> server!
>
>
>
> But why? How can a $1,000+ enterprise level switch have a problem like
> this?
>
>
>
> Well, as it turns out, it wasn’t the fault of the switch at all. See:
> 224.0.1.[1-10] have reserved internet protocols on them:
>
> http://www.networksorcery.com/enp/protocol/ip/multicast.htm
>
>
>
> For those of you who don’t like to understandably click on links from
> strangers (and geeky meteorologists):
>
>
>
>
> INTERNETWORK CONTROL BLOCK
>
>
>
> *224.0.1.0*
>
> VMTP <http://www.networksorcery.com/enp/protocol/vmtp.htm> Managers.
>
> RFC 1045
>
> *224.0.1.1*
>
> NTP <http://www.networksorcery.com/enp/protocol/ntp.htm>, Network Time
> Protocol.
>
> RFC 1119 <http://www.networksorcery.com/enp/rfc/rfc1119.pdf>
>
> *224.0.1.2*
>
> SGI-Dogfight.
>
>
>
> *224.0.1.3*
>
> Rwhod.
>
>
>
> *224.0.1.4*
>
> VNP.
>
>
>
> *224.0.1.5*
>
> Artificial Horizons - Aviator.
>
>
>
> *224.0.1.6*
>
> NSS, Name Service Server.
>
>
>
> *224.0.1.7*
>
> AUDIONEWS - Audio News Multicast.
>
>
>
> *224.0.1.8*
>
> SUN NIS+ Information Service.
>
>
>
> *224.0.1.9*
>
> MTP <http://www.networksorcery.com/enp/protocol/mtp.htm>, Multicast
> Transport Protocol.
>
> RFC 1301 <http://www.networksorcery.com/enp/rfc/rfc1301.txt>
>
> *224.0.1.10*
>
> IETF-1-LOW-AUDIO.
>
>
> Uh huh. When the NWS picked those IP addresses to encapsulate the data,
> they picked IP numbers that are used and reserved for enterprise-level
> switches.
>
>
>
> As for the College of DuPage? I just got this email from head network
> engineer, Dave Bukowski, who came up with this solution: you need to enable
> unknown multicast flooding on those IP’s. Here’s what Dave did, and his
> email with the solution:
>
> -----------
>
> FOUND IT!!!!
>
>
>
>
>
> This was in the config
>
>
>
> show running-config
>
> .....SNIP.....
>
> !
>
> ! *** IGMP ***
>
> !
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.1
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.2
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.3
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.4
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.5
>
> vlan igmp unknown-mcast-no-flood enable
>
> .....ENDSNIP.....
>
>
>
>
>
> Added
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.6
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.7
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.8
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.9
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.10
>
> vlan igmp unknown-mcast-allow-flood 224.0.1.201
>
>
>
>
>
>
>
> So now:
>
>
>
> SDBDF01#show vlan igmp unknown-mcast-allow-flood
>
> Allowed Multicast Addresses
>
> -----------------------------------------------------------------------
>
> 224.0.1.1 224.0.1.2 224.0.1.3 224.0.1.4
>
> 224.0.1.5 224.0.1.6 224.0.1.7 224.0.1.8
>
> 224.0.1.9 224.0.1.10 224.0.1.201
>
> Total Multicast MAC Addresses: 0
>
> Total Multicast IP Addresses: 11
>
>
>
>
>
> Now we have a flood of data coming in on both noaaport1 and noaaport2. It
> was multicast and we were blocking the flood, but had to specifically allow
> the flooding by multicast address.
>
>
>
> -Dave
>
>
>
>
> Thanks, Dave. We spent at least 10 hours trying to figure this out. On a
> $50 switch, you might not have a problem, but if you do decide to have
> multiple ingesters by going through a network switch…if you don’t get all
> of the data, your reception may be fine…it’s the switch that’s been
> programmed to stop the flow of data.
>
>
>
> Thanks to Tom Yoksas as he helped us try to figure this mess out, to Mike
> Zuranski for going out in the bitter cold and spending hours on the phone
> as we tried to figure this out, and for Dave Bukowski who ran the ball for
> the touchdown after we discovered it was the switch blocking the data.
>
>
>
> Gilbert
>
> *Gilbert Sebenste*
>
> Staff Meteorologist
>
>
>
> Environmental Health and Safety
>
> Labs for Wellness 154 | DeKalb, Illinois 60115
>
> 815-753-5492 <(815)%20753-5492>
>
> *gilbert@xxxxxxx <gilbert@xxxxxxx>*
>
> http://weather.admin.niu.edu
>
> Everyone. Home. Safely.
>
>
>
> [image: NIU]
>
>
>
>
>
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--
Gerry Creager
NSSL/CIMMS
405.325.6371
++++++++++++++++++++++
“Big whorls have little whorls,
That feed on their velocity;
And little whorls have lesser whorls,
And so on to viscosity.”
Lewis Fry Richardson (1881-1953)
