[Outages-discussion] [outages] Comcast Issues Central & East

[Rusty Dekema]

[I hope this message is appropriate for outages-discussion. I believe
it is, but please let me know if it is not and I will note it for the
future.]

I'm not sure this explains the support call you described, but for
Comcast customers with static IPv4 blocks (and if you order a single
static IP from them, it gets implemented as a routed /30 to your
premises), the IPv4 block is actually configured directly on the
Comcast-provided consumer-premises "gateway" (cable modem + router
combo) device.

When the gateway boots, its modem attempts to connect to the DOCSIS RF
network. Once it does, the router pulls a dynamic IP address via DHCP
and uses RIPv2 to announce its LAN-side IPv4 block toward whatever
Comcast router is on the other side of the RF network. (This
announcement is authenticated via a secret which Comcast configures in
your gateway at the same time they configure the IPv4 block which,
incidentally, I believe explains why they will not let you use a
regular DOCSIS modem connected to your own router with this service -
they don't want to tell you the secret, or probably to deal with
customers who don't know how to configure their routers.)

Obviously the routes to these tiny blocks get summarized within
Comcast's network at some point and, for my service, that point
appears to be in Chicago based on traceroutes from various locations
during this and other localized outages.

-Rusty



On Wed, Jul 31, 2019 at 12:27 PM Joe Klein via Outages
<outages at outages.org> wrote:
>
> I know that Comcast's edge will block incoming traffic if a customer's 'modem' is offline.
>
> That was an interesting support call once. The line was up and we could hit some stuff (on-net) from the location but off-net was dead and all traceroutes to them from off-net died one-two hops after crossing into Comcast. Power cycling the modem re-registered it with whatever database their edge uses to and sorted everything.
>
>
>
> -----Original Message-----
> From: Outages <outages-bounces at outages.org> On Behalf Of Rusty Dekema via Outages
> Sent: Wednesday, July 31, 2019 12:01
> To: Jordan Morris <jmorris at crosswindvoip.com>
> Cc: outages at outages.org
> Subject: Re: [outages] Comcast Issues Central & East
>
> It is unclear to me whether this is related, but my Comcast "business"
> (DOCSIS) line in southeast Michigan went completely down around 10:43 a.m., Eastern Daylight Time (UTC-4) this morning.
>
> Comcast's website said that this was a known outage and gave an estimated restoration time of approximately three hours.
>
> In reality, the service came back up around 10:55 a.m.
>
> During the outage, the route to my /28 seemed to have been withdrawn from Comcast's internal network; traceroutes toward it from the Chicago area died within Comcast's network in the Chicago area. I was not physically present at the premises, so I was unable to determine whether this was a local / layer 1 / physical plant problem, or part of a wider problem.
>
> -Rusty
>
>
> On Wed, Jul 31, 2019 at 10:12 AM Jordan Morris via Outages <outages at outages.org> wrote:
> >
> > Anyone else seeing issues with Comcast on the Central and East coast. We are seeing packet loss with on Comcast connections connecting to devices on the West coast. Getting lots of alerts for our monitoring on the West to Central but clean on our Central to Central monitoring.
> >
> >
> >
> >
> >
> >
> >
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