Hi there,
I have been a VM customer for years and until recently was on 20Mbit. I came back from holiday and then my connection kept dropping.
An engineer came around and installed a SuperHub, which I use in modem only. The same symptoms were exhibited just a day or two later. An engineer came around again and installed a SuperHub 2 and changed some connections outside.
I am running the SuperHub 2 as a Modem only. This goes in to my Linux server. On this box I have DHCP, DNS and iptables to masquerade the connection and forward it on to clients.
The VM engineer that came around last time was a Supervisor and said that as I was using my own equipment, they were unable to see what is going wrong. I fail to understand why this is the case. The SuperHub is still at the forefront of the network, so they should be able to get their readings just fine. I wasn't too impressed with him. The other engineer was able to put me into modem only mode wirelessly, so that I did not need to physically connect the SuperHub and accidentally double NAT myself. The other 'Supervisor' spent around 10 minutes trying to login to 192.168.1.1 and then 'refused' to assist because I have a server. One thing I would like some clarification with: he said that because he was reading no T(x) timeouts, the system was fine. Are these timeouts persistent across reboots in the SuperHub? He told me that they were, and that it meant my connection was perfect. But I really don't believe this...
Nonetheless, during periods of downtime, I have attached the cable directly in to a Windows PC, just to make sure things are normal, but have not had any improvement either.
My symptoms are that the network just 'drops' offline. During this time, a ping to 8.8.8.8 will return me a 'Host destination unreachable'. I am unable to ping 192.168.100.1 (the SH in Modem Only mode) or resolve the page either during this time.
I have noticed from running tcpdump on 67 that Virgin Media's DHCP servers seem extremely slow to respond to discovers. My guess would be that the SNR is dropping temporarily, then my SH is taking a long time to resynchronise with the network. I noticed that removing the coax from the SH and reconnecting it will not result in automatically re-establishing the connection, so this may support this idea.
This has been going on for two weeks now and is quite frustrating. I want this fixed, but I'm not sure how to diagnose this one. Connection went down typing this...
Here are my numbers when my connection is up. I have a 6Db FPA on my SH.
Here is my routing information. My IP is: 82.14.218.xxx
Code:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default cpc3-croy21-2-0 0.0.0.0 UG 0 0 0 eth1
default precise.sam 0.0.0.0 UG 100 0 0 eth0
82.14.216.0 * 255.255.252.0 U 0 0 0 eth1
localnet * 255.255.255.0 U 0 0 0 eth0
192.168.122.0 * 255.255.255.0 U 0 0 0 virbr0
and I added the following ifup.d rule to add the correct routing information, because it seems it has never been acquired from DHCP since I've been using this box in 2012.
Code:
post-up route add default gw 82.14.218.1
pre-down route del default gw 82.14.218.1
So, where do I go from here?
Many thanks,
Sam
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