Full Disclosure mailing list archives
Re: is my ISP lying or stupid?
From: Valdis.Kletnieks () vt edu
Date: Sun, 18 Mar 2012 11:47:15 -0400
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...
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Current thread:
- Re: is my ISP lying or stupid?, (continued)
- Re: is my ISP lying or stupid? Julius Kivimäki (Mar 16)
- 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? 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)