Full Disclosure mailing list archives
Re: is my ISP lying or stupid?
From: James Condron <james () zero-internet org uk>
Date: Sun, 18 Mar 2012 16:09:31 +0000
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 () vt edu wrote:
On Sun, 18 Mar 2012 12:49:49 -0000, Peter Maxwell said:On 16 March 2012 19:11, Dave <iryshman () gmail com> 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... _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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Current thread:
- Re: is my ISP lying or stupid?, (continued)
- Re: is my ISP lying or stupid? rancor (Mar 16)
- Re: is my ISP lying or stupid? James Condron (Mar 16)
- Re: is my ISP lying or stupid? Valdis . Kletnieks (Mar 16)
- Re: is my ISP lying or stupid? gold flake (Mar 16)
- Re: is my ISP lying or stupid? James Condron (Mar 16)
- Re: is my ISP lying or stupid? rancor (Mar 16)
- Re: is my ISP lying or stupid? Nick FitzGerald (Mar 16)
- Re: is my ISP lying or stupid? Peter Maxwell (Mar 17)
- Re: is my ISP lying or stupid? Thor (Hammer of God) (Mar 17)
- Re: is my ISP lying or stupid? Dave (Mar 18)
- Re: is my ISP lying or stupid? Peter Maxwell (Mar 18)
- Re: is my ISP lying or stupid? Valdis . Kletnieks (Mar 18)
- Re: is my ISP lying or stupid? James Condron (Mar 18)
- Re: is my ISP lying or stupid? Lee (Mar 18)
- Re: is my ISP lying or stupid? _ (Mar 21)
- Re: is my ISP lying or stupid? Giles Coochey (Mar 21)
- Re: is my ISP lying or stupid? Thor (Hammer of God) (Mar 21)
- Re: is my ISP lying or stupid? Alex Buie (Mar 23)
- Re: is my ISP lying or stupid? Peter Maxwell (Mar 18)