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One client is unable to access the CentOS server (can't ping or http).

Checking the rules in APF 9.7 (apf -l) and there seems no specific rule defined. tracert shows each step and connection fine until the server is reached.

How can I resolve the problem and unblock the client? If there is any additional details required I will edit and add to the post, I am not sure what to check next.


The client is assigned IP addresses in 2 ranges (both with the same ISP), 88.111.x.x and 79.69.x.x. The connection works when connected from 79.69.x.x.

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Does tcpdump show any traffic for that client? – cjc Aug 28 '12 at 19:46
Are you seeing traffic from other clients on the same subnet as the problematic one? – jgoldschrafe Aug 28 '12 at 20:26
@jgoldschrafe - no traffix from any on that subnet but that might be due to insufficient traffic. – Nick Aug 29 '12 at 20:53
@cjc - I am waiting to find out when they are on at the same time (we are in different timezones). – Nick Aug 29 '12 at 20:55
Did you check the route back from the server to the clients ? I'd bet that this is a local routing issue. – Stephane Aug 31 '12 at 11:48
  1. Does this only affect a particular client?

If yes: could be their firewall If no: Can you access said server from varying locations (home, office, vps @ come provider)?

I would advise checking if you can access the server from at least 3 locations (home, office vps) if this is the case then advise the client that the issue may be to do with their corporate firewall and to liase with the relevant support team ... given more information on my points above I can provide more insight :)

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It is a fairly well used server with around 1-2k different clients per day. I can certainly access it from any location I have tried. – Nick Aug 28 '12 at 23:40
@Nick I'd be inclined to suggest the issue therefor is on the clients network, can they provide a traceroute for instance? – Oneiroi Aug 29 '12 at 8:42
Hi, the traceroute shows correctly each step until the final step which gets no response. – Nick Aug 29 '12 at 20:54
@Nick what is the final device to give a response? the "edge" router into the server network or something else? – Oneiroi Aug 29 '12 at 22:02
yes it is the edge router before the server. – Nick Aug 30 '12 at 10:47

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