Re: [Full-disclosure] is my ISP lying or stupid?

[James Condron <james@xxxxxxxxxxxxxxxxxxxx>]

 Sorry, I don't mean to be rude but none of that made any sense, especially 
from an ISP perspective.

You will never have a switch per area; it doesn't work like that, you'll have a 
series of distribution routers for routing to customers. Mail, www, shell, SIP, 
whatever will be other services which of course are on one to a milloin 
switches.  Really doesn't matter as this has nothing to do with anything.

The routers of an ISP are sorta DHCP in the sense that the IPs are dynamic- 
DHCP really works as one network whereas an ISP switch will have a series of 
/30 vlans for obvious reasons. Getting an IP and connection is more complex 
than that but already we're down to a series of routers.

Somewhere in a datacenter (Lets keep it simple for now) is a cabinet with a 
bunch of servers in; one will do customer web space and so on. This cabinet 
will have a switch in and either this went or the router it is connected to.

They're not using teaming. They're not using loadbalancers. 17^39 is a bit of a 
weird one to even have to type out.

Somewhere someone pulled the wrong cable or someone broke a route. These are 
the two things which cause (In my experience) almost all of ISP issues. That or 
a switch died.

And whether they meant switch or not they said switch. Chances are they lost a 
blade or an SFP or whatever.

On 18 Mar 2012, at 15:47, Valdis.Kletnieks@xxxxxx wrote:

> On Sun, 18 Mar 2012 12:49:49 -0000, Peter Maxwell said:
>> On 16 March 2012 19:11, Dave <iryshman@xxxxxxxxx> wrote:
>>> Your ISP probably has their users are on different networks than their
>>> servers.  Sounds like maybe they meant the switch you are on, not the
>>> servers switch.  Need to troubleshoot, use a smart phone or some other OOB
>>> capable device to test access to the ISP servers.  If you can access OOB,
>>> then maybe they aren't lying.  Just a guess, you didnt provide much detail.
> 
>> Unlikely, usually these switches are quite large and when a user has OOB it
>> usually means console access to the server, i.e. nothing to do with network
>> topology.
> 
> I strongly suspect that what Dave meant was:
> 
> 1) There's a switch at the ISP's central site that the services live on.
> 2) There's *another* switch that you and the other subscribers in your
> area are connected to.
> 3) If you can reach the mail server via other means (IP-capable cellphone,
> wireless from the local McDonalds, etc), it's more likely switch (2) than (1).
> 
> The real troubleshooting fun starts when you throw things like load balancers
> and ethernet bonding into the the config.  Nice things if they work, but can 
> be
> a bear to diagnose.  If they're doing round-robin, they can end up hosing 
> every
> N'th connection (which is loads of fun when N is in the hundreds).  The other
> common failure mode is hashing each inbound's address to determine which back
> end to go to and certain hash values end up in the bit bucket - so it all 
> works
> great unless your DHCP-supplied IP address is (when treated as a 32-bit 
> number)
> equal to 17 mod 39 or some siimilarl wierdness.  The troubleshooting fun gets
> even worse if the hash contains both the IP and the ephemeral port number - 
> this
> can result in intermittent issues that will take *month* to find and 
> diagnose, because
> most users will just hit reload, and since the ephemeral port on their end 
> changed,
> it works for them and they never report it...
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Full-Disclosure - We believe in it.
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