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  • [SOLVED] netcat/socat no response from other networking services

    - by jack
    Hi gurus First, I thought that this was Vmware problem : http://serverfault.com/questions/141838/vmware-problems-networking-no-packet-response But now, after testing on several physical machines, I realized certain services didn't return response data when using socat/netcat 1.1 which is supposed to the latest version since last updated. root@test3:~# netcat 192.168.1.2 25 220 762462a8c4d Microsoft ESMTP MAIL Service, Version: 6.0.2600.5949 ready at Fri, 12 May 2010 18:04:20 +0600 EHLO localhost sdfsafsd ^ root@test3:~# I've tested it on both windows and linuxes. I found no problem with telnet.

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  • LDAP over SSL with an EFI Fiery printer

    - by austinian
    I've got a printer with a Fiery running 8e Release 2. I can authenticate users against AD using the LDAP configuration, but I can only get it to work if I don't use SSL/TLS, and only if I use SIMPLE authentication. Right now, it's authenticating using a fairly low-impact user, but it's also the only system on our network that's not using LDAPS. I can get AD info fine over LDAPS using ldp.exe from my machine, our firewall, our mail filter, our linux boxes, etc. The only problem child is the Fiery. I've added the LDAP server certificate as a trusted cert to the Fiery, but after I check the box for Secure Communication and change the port to 636, pressing Validate results in a dialog box coming up saying: LDAP Validation Failed Server Name invalid or server is unavailable. I've tried changing the server name to use just the name, the FQDN, and the IP address, and changed it to another server, just to see if it was just this AD server that was fussy with the Fiery. EDIT: removed LDP output, added packet capture analysis from wireshark: The conversation seems pretty normal to me, up to the point where the Fiery terminates the connection after the server sends back a handshake response. Maybe they messed up their TLS implementation? I'm trying support, but it's been fairly useless so far. The cert is a SHA-2 (sha256RSA) 2048-bit certificate. Also, it looks like the Fiery is specifying TLS 1.0. Looking at http://msdn.microsoft.com/en-us/library/windows/desktop/aa374757(v=vs.85).aspx, I'm not seeing SHA256 and TLS 1.0 combination being supported by SChannel. headdesk perhaps that's why, after the DC changes the cipher spec, the connection is terminated by the Fiery? TLS 1.1 and 1.2 are enabled on the DC. Wireshark conversation: DC: 172.17.2.22, Fiery: 172.17.2.42 No. Time Source Source Port Destination Destination Port Protocol Length Info 1 0.000000000 172.17.2.42 48633 172.17.2.22 ldaps TCP 74 48633 > ldaps [SYN] Seq=0 Win=5840 Len=0 MSS=1460 SACK_PERM=1 TSval=3101761 TSecr=0 WS=4 2 0.000182000 Dell_5e:94:e3 Broadcast ARP 60 Who has 172.17.2.42? Tell 172.17.2.22 3 0.000369000 TyanComp_c9:0f:90 Dell_5e:94:e3 ARP 60 172.17.2.42 is at 00:e0:81:c9:0f:90 4 0.000370000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 74 ldaps > 48633 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1 TSval=67970573 TSecr=3101761 5 0.000548000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [ACK] Seq=1 Ack=1 Win=5840 Len=0 TSval=3101761 TSecr=67970573 6 0.001000000 172.17.2.42 48633 172.17.2.22 ldaps TLSv1 147 Client Hello 7 0.001326000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 1514 [TCP segment of a reassembled PDU] 8 0.001513000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 1514 [TCP segment of a reassembled PDU] 9 0.001515000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [ACK] Seq=82 Ack=1449 Win=8736 Len=0 TSval=3101761 TSecr=67970573 10 0.001516000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [ACK] Seq=82 Ack=2897 Win=11632 Len=0 TSval=3101761 TSecr=67970573 11 0.001732000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 1514 [TCP segment of a reassembled PDU] 12 0.001737000 172.17.2.22 ldaps 172.17.2.42 48633 TLSv1 1243 Server Hello, Certificate, Certificate Request, Server Hello Done 13 0.001738000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [ACK] Seq=82 Ack=4345 Win=14528 Len=0 TSval=3101761 TSecr=67970573 14 0.001739000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [ACK] Seq=82 Ack=5522 Win=17424 Len=0 TSval=3101761 TSecr=67970573 15 0.002906000 172.17.2.42 48633 172.17.2.22 ldaps TLSv1 78 Certificate 16 0.004155000 172.17.2.42 48633 172.17.2.22 ldaps TLSv1 333 Client Key Exchange 17 0.004338000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 66 ldaps > 48633 [ACK] Seq=5522 Ack=361 Win=66304 Len=0 TSval=67970573 TSecr=3101762 18 0.004338000 172.17.2.42 48633 172.17.2.22 ldaps TLSv1 72 Change Cipher Spec 19 0.005481000 172.17.2.42 48633 172.17.2.22 ldaps TLSv1 327 Encrypted Handshake Message 20 0.005645000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 66 ldaps > 48633 [ACK] Seq=5522 Ack=628 Win=66048 Len=0 TSval=67970574 TSecr=3101762 21 0.010247000 172.17.2.22 ldaps 172.17.2.42 48633 TLSv1 125 Change Cipher Spec, Encrypted Handshake Message 22 0.016451000 172.17.2.42 48633 172.17.2.22 ldaps TCP 66 48633 > ldaps [FIN, ACK] Seq=628 Ack=5581 Win=17424 Len=0 TSval=3101765 TSecr=67970574 23 0.016630000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 66 ldaps > 48633 [ACK] Seq=5581 Ack=629 Win=66048 Len=0 TSval=67970575 TSecr=3101765 24 0.016811000 172.17.2.22 ldaps 172.17.2.42 48633 TCP 60 ldaps > 48633 [RST, ACK] Seq=5581 Ack=629 Win=0 Len=0

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  • Is there any USB2.0 data transfer chunk size limit?

    - by goldenmean
    With one read() or write() at a time, can we increase the bulk data size over USB interface? For example, I want to transfer chunk of 1024 (1K) bytes data and if the device has limitations of only 64bytes, is there any way I can increase the packet size for read() and write() system call over USB? Is there any limitation on size of data transfer over USB in a host-device environment?

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  • how does ospf control flooding?

    - by iamrohitbanga
    what method is used by ospf protocol to prevent looping of flooded packets for link state advertisements? The packet header does not contain any timestamp. How do the routers recognize that it is the same advertisement that they sent before?

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  • Why do these ipfw delayed pipes have no effect?

    - by troutwine
    I'm on OSX 10.7.5 and am attempting to add some latency to the connection to my personal domain with ipfw, using this article as a guide. Normal latency: > ping -c5 troutwine.us PING troutwine.us (198.101.227.131): 56 data bytes 64 bytes from 198.101.227.131: icmp_seq=0 ttl=56 time=92.714 ms 64 bytes from 198.101.227.131: icmp_seq=1 ttl=56 time=91.436 ms 64 bytes from 198.101.227.131: icmp_seq=2 ttl=56 time=91.218 ms 64 bytes from 198.101.227.131: icmp_seq=3 ttl=56 time=91.451 ms 64 bytes from 198.101.227.131: icmp_seq=4 ttl=56 time=91.243 ms --- troutwine.us ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 91.218/91.612/92.714/0.559 ms Enabling ipfw: > sudo sysctl -w net.inet.ip.fw.enable=0 net.inet.ip.fw.enable: 1 -> 0 > sudo sysctl -w net.inet.ip.fw.enable=1 net.inet.ip.fw.enable: 0 -> 1 The configuration of the pipe: > sudo ipfw add pipe 1 ip from any to 198.101.227.131 00200 pipe 1 ip from any to any dst-ip 198.101.227.131 > sudo ipfw add pipe 2 ip from 198.101.227.131 to any 00500 pipe 2 ip from 198.101.227.131 to any > sudo ipfw pipe 1 config delay 250ms bw 1Mbit/s plr 0.1 > sudo ipfw pipe 2 config delay 250ms bw 1Mbit/s plr 0.1 The pipes are in place and configured: > sudo ipfw -a list 00100 166 14178 fwd 127.0.0.1,20559 tcp from any to me dst-port 80 in 00200 0 0 pipe 1 ip from any to 198.101.227.131 00300 0 0 pipe 2 ip from 198.101.227.131 to any 65535 37452525 32060610029 allow ip from any to any > sudo ipfw pipe list 00001: 1.000 Mbit/s 250 ms 50 sl.plr 0.100000 0 queues (1 buckets) droptail mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000 00002: 1.000 Mbit/s 250 ms 50 sl.plr 0.100000 0 queues (1 buckets) droptail mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000 Yet, this has had no effect: > ping -c5 troutwine.us PING troutwine.us (198.101.227.131): 56 data bytes 64 bytes from 198.101.227.131: icmp_seq=0 ttl=56 time=100.920 ms 64 bytes from 198.101.227.131: icmp_seq=1 ttl=56 time=91.648 ms 64 bytes from 198.101.227.131: icmp_seq=2 ttl=56 time=91.777 ms 64 bytes from 198.101.227.131: icmp_seq=3 ttl=56 time=91.466 ms 64 bytes from 198.101.227.131: icmp_seq=4 ttl=56 time=93.209 ms --- troutwine.us ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 91.466/93.804/100.920/3.612 ms What gives? I understand that ipfw is depreciated, but the manpage does not mention it being disabled. Also, I am not using Network Link Controller as I want to affect a single host.

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  • What exactly does ssh send when performing key negotiation?

    - by Checkers
    When explicitly specifying identity file to ssh: ssh -i ./id_rsa ... I have these lines in ssh debug trace: debug1: Offering public key: ./id_rsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply Does it mean ssh-generated id_rsa contains public RSA exponent as well, or ssh is sending out my private key? (which, of course, does not make sense). id_rsa format seems to be rather explicit that it contains private key with its "BEGIN PRIVATE KEY" block.

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  • Satellite data in Russia?

    - by Eddy
    Anyone familiar with options for transmitting data in Russia? I'd be interested in hearing about low-speed packet data and faster. Not really looking at VSAT initially as I'd like to keep the power requirements low unless we find no other options.

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  • iproute2 premptive route creation, i think....

    - by Bryan Hunt
    Firstly: I know could do this the easy way with SSH but I want to learn how to route. I want to route packets back through the same tun0 interface from which they came into my system. I can do it for single routes. This works: sudo ip route add 74.52.23.120 metric 2 via 10.8.0.1 But i'd have to add them manually for each request that came down the pipe I've taken the blue pill and followed the http://lartc.org/howto/lartc.netfilter.html: Netfilter & iproute - marking packets tutorial But it's oriented towards redirecting OUTGOING packets based upon markers What I want is for a packet that comes in via tun0 not to be dropped which is what's happening right now, running scappy or suchlike to receive packets it doesn't seem to be receiving anything. Watching in wireshark I see the initial SYN packets coming in on the tun0 interface but that's as far as it gets without a static route as shown above. Am I nuts?

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  • Encrypting traffic on remote end of SSH tunnel

    - by Aaron
    Using an example of someone connecting to a VPS, an SSH tunnel will encrypt any traffic coming from the user to the VPS. Once it reaches the VPS network, the traffic is not encrypted and is easily sniffable by network administrators on that particular network. (am I understanding all that correctly?) Is there a way to have the traffic encrypted on both ends so that neither side is susceptible to packet sniffing to reveal what kind of data/traffic/protocol is being transmitted?

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  • Connection to mysql server in SYN_SENT

    - by Sunil
    We are facing a strange problem from last few days between our application server and database server(Mysql): connection to database server from application server hangs in SYN_SENT state and after that we are not able to make any connection to database server on mysql port(3306). When we checked the netstat output on database server its in SYN_RECV state. What I can figure out is mysql server is receiving the SYN request and responding also and its not reaching to the client hence SYN_RECV at server side and SYN_SENT at client side. I think SYN_SENT state should go after some time and because of this other db connection attempts to same server should not hang. Does anybody have any idea how can we resolve this issue? Out setup details : Application server: RHEL 5.4, kernel-release = 2.6.18-164.el5, x86_64 Database server: Mysql Version : 5.1.49 RHEL 5.4, kernel-release = 2.6.18-164.el5, x86_64

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  • Is my Cisco switch port bad?

    - by ewwhite
    I've been chasing a packet-loss and network stability issue for a handful of end-users on an internal network for the past few days... These issues surfaced last week, however the location was struck by lightning six weeks ago. I was seeing 5-10% packet loss between a stack of four Cisco 2960's and several PC's and phones on the other side of a 77-meter run. The PC's were run inline with the phones over a trunked link (switchport configuration pastebin). We were seeing dropped calls and interruptions in client-server applications and Microsoft Exchange connectivity. I tried the usual troubleshooting steps remotely, having a local technician do the following during breaks in user and production activity: change cables between the wall jack and device. change patch cables between the patch panel and switch port(s). try different switch ports within the 2960 stack. change end-user devices with known-good equipment (new phones, different PC's). clear switch port interface counters and monitor incrementing errors closely. (Pastebin output of sh int) Pored over the device logs and Observium RRD graphs. No link up/down issues from the switch side. change power strips on the end-user side. test cable runs from the Cisco 2960 using test cable-diagnostics tdr int Gi4/0/9 (clean)* test cable runs with a Tripp-Lite cable tester. (clean) run diagnostics on the switch stack members. (clean) In the end, it took three changes of switch ports to find a stable solution. The only logical conclusion is that a few Cisco 2960 switch ports are bad or flaky... Not dead, but not consistent in behavior either. I'm not used to seeing individual ports die in this manner. What else can I test or check to determine if these devices are bad? Is it common for single ports to have problems, rather than a contiguous bank of ports? BTW - show cable-diagnostics tdr int Gi4/0/14 is very cool... Interface Speed Local pair Pair length Remote pair Pair status --------- ----- ---------- ------------------ ----------- -------------------- Gi4/0/14 1000M Pair A 79 +/- 0 meters Pair B Normal Pair B 75 +/- 0 meters Pair A Normal Pair C 77 +/- 0 meters Pair D Normal Pair D 79 +/- 0 meters Pair C Normal

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  • Win 2k3 - DNS query ?

    - by nXqd
    I'm learning about network and I configured DNS in 2k3. In forward zone : cntt.edu www.cntt.edu [ 192.168.188.4 ] . [ All IP / DNS configuration is right ] After that I use wireshark to catch packet when I enter www.cntt.edu in IE . I see there's no DNS here, I forward directly to 192.168.188.4, there's no query . Any problem ? Thanks for reading this :)

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  • Ubuntu: Multiple NICs, one used only for Wake-On-LAN

    - by jcwx86
    This is similar to some other questions, but I have a specific need which is not covered in the other questions. I have an Ubuntu server (11.10) with two NICs. One is built into the motherboard and the other is a PCI express card. I want to have my server connected to the internet via my NAT router and also have it able to wake from suspend using a Magic Packet (henceforth referred to as Wake-On-LAN, WOL). I can't do this with just one of the NICs because each has an issue - the built-in NIC will crash the system if it is placed under heavy load (typically downloading data), whilst the PCI express NIC will crash the system if it is used for WOL. I have spent some time investigating these individual problems, to no avail. My plan is thus: use the built-in NIC solely for WOL, and use the PCI express card for all other network communication except WOL. Since I send the WOL Magic Packet to a specific MAC address, there is no danger of hitting the wrong NIC, but there is a danger of using the built-in NIC for general network access, overloading it and crashing the system. Both NICs are wired to the same LAN with address space 192.168.0.0/24. The built-in ethernet card is set to have interface name eth1 and the PCI express card is eth0 in Ubuntu's udev persistent rules (so they stay the same upon reboot). I have been trying to set this up with the /etc/network/interfaces file. Here is where I am currently: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.0.3 netmask 255.255.255.0 network 192.168.0.0 broadcast 192.168.0.255 gateway 192.168.0.1 auto eth1 iface eth1 inet static address 192.168.0.254 netmask 255.255.255.0 I think by not specifying a gateway for eth1, I prevent it being used for outgoing requests. I don't mind if it can be reached on 192.168.0.254 on the LAN, i.e. via SSH -- it's IP is irrelevant to WOL, which is based on MAC addresses -- I just don't want it to be used to access internet resources. My kernel routing table (from route -n) is Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.0.1 0.0.0.0 UG 100 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 My question is this: Is this sufficient for what I want to achieve? My research has thrown up the idea of using static routing to specify that eth1 should only be used for WOL on the local network, but I'm not sure this is necessary. I have been monitoring the activity of the interfaces using iptraf and it seems like eth0 takes the vast majority of the packets, though I am not sure that this will be consistent based on my configuration. Given that if I mess up the configuration, my system will likely crash, it is important to me to have this set up correctly!

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  • mysql-proxy got error which cause it to crash

    - by nonus25
    I got that message and i dont know what it is means: Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) last message repeated 98 times Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) network-mysqld-packet.c.596: COM_(0x04) should not be (OK|ERR|NULL), got: 00 Oct 21 12:24:26 lex kernel: [4163416.207121] mysql-proxy[14271] trap int3 ip:7ff96e8a4313 sp:7fffb9086ad0 error:0 Any idea what can be the cause of it ?

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  • Is Hacom Mars II Dual Blade good ?

    - by Joachim H. Skeie
    I am considering getting a Hacom Mars II Dual Blade for use as a firewall in a data-center for one of my colocated solutions. As the 1U enclosure have two identical firewalls, I am intending to use one of the firewalls as the external firewall using packet-filtering and load balancer (balancing load for my front-end nodes), while using the second as the internal firewall (as an application gateway). But I have no experience with Hacom, or pfSense firewalls. They do look really good on paper, but how are they in practice ?

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  • I am unable to connect to my netbook from any machine on my network until the netbook has pinged it

    - by Samuel Husky
    I have a rather strange issue with my netbook on my local network. When trying to connect to it in any way from a remote system it does not appear to find it. However if I get the netbook to ping the machine trying to connect it mystically appears to work. Below is the ping test from my main PC to the netbook. C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Now a ping from the netbook to my main PC sam@malamute ~ $ ping 192.168.8.100 PING 192.168.8.100 (192.168.8.100) 56(84) bytes of data. 64 bytes from 192.168.8.100: icmp_req=1 ttl=128 time=2.46 ms 64 bytes from 192.168.8.100: icmp_req=2 ttl=128 time=0.835 ms 64 bytes from 192.168.8.100: icmp_req=3 ttl=128 time=1.60 ms 64 bytes from 192.168.8.100: icmp_req=4 ttl=128 time=1.32 ms 64 bytes from 192.168.8.100: icmp_req=5 ttl=128 time=1.34 ms ^C --- 192.168.8.100 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4004ms rtt min/avg/max/mdev = 0.835/1.514/2.460/0.536 ms And the same ping again from the main PC after the netbook has made a connection to it C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 1ms, Average = 1ms The netbook is running Gentoo and is currently connected via wireless. My main PC is running Windows 7 however I get the same result no matter what PC I use on this network. Please see this example from a CentOS machine on the same network [root@tiger ~]# ping 192.168.8.102 PING 192.168.8.102 (192.168.8.102) 56(84) bytes of data. From 192.168.8.200 icmp_seq=2 Destination Host Unreachable From 192.168.8.200 icmp_seq=3 Destination Host Unreachable From 192.168.8.200 icmp_seq=4 Destination Host Unreachable --- 192.168.8.102 ping statistics --- 6 packets transmitted, 0 received, +3 errors, 100% packet loss, time 5000ms , pipe 3 If you need any more information or require logs or config files please let me know and any assistance is greatly appreciated. Additional info: No responses on TCP dump from the netbook. Same result when booting into Ubuntu from a USB key. No issue when using a wired Ethernet connection.

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  • Windows 2008 Routing and Remote access server - access to the internet

    - by Ian
    I have a windows 2008 r2 remote access server set up and running. The remote access works fine. My problem is that the remote access server itself doesn't have access to the internet. The box has two interfaces, an internal and an external. Inbound connections come in on the external interface and RRAS responds. All wall and nice. I want to be able to use windows update, browse, etc from this box but can't as the outbound traffic just gets blocked. I've tried going into the RRAS mmc tool and opening the interface properties, under which there are two buttons for inbound and outbound filters. There I tried adding ports 80 and 443, but this doesn't work completely. I can see the connection initiating (Syn goes out) but the session never establishes itself. Anyone done this or got any suggestions?

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  • Virus blocking incoming connections ?

    - by Benoît
    Hello, on my windows 2003 server, all incoming connections are dropped. I can see them getting in using Wireshark, but even a single ping from another computer fails. All locally initiated connection work fine (i'm asking from the server). This server is the DC/DHCP/DNS/File server, so computer clients are in the dark. I've run varius antivirus and removal tools without any luck. The Windows Firewall is disabled. I'm wild-guessing at some virus/worm. How can i check why these incoming ICMP/TCP SYN/etc are dropped ? Anyone has any knowledge about such situations ? Thanks.

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  • PHP web application can't connect mysql installed with Zend Server CE on Mac OSX

    - by Kane
    I'm setting up development environment on Mac OSX. However the PHP web application can't connect the mysql server installed with Zend Server CE. The error information is below, [Type] dbnot_connect [2013] Lost connection to MySQL server at 'reading initial communication packet', system error: 61 Mysql database can be accessed via phpAdmin installed with Zend Server CE as well. The same code works well on Windows or Linux in Zend Server CE.

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  • Server currently under DDOS, not sure what to do.

    - by Volex
    Hi, My web server is currently under a DDOS attack I believe, the messages log is full of these kind of messages: May 13 15:51:19 kernel: nf_conntrack: table full, dropping packet. May 13 15:51:19 last message repeated 9 times May 13 15:51:24 kernel: __ratelimit: 78 callbacks suppressed May 13 15:51:24 kernel: nf_conntrack: table full, dropping packet. May 13 15:52:06 kernel: possible SYN flooding on port 80. Sending cookies. and a netstat has a huge amount of the following: tcp 0 0 my.host.com:http bb176da0.virtua.com.br:4998 SYN_RECV tcp 0 0 my.host.com:http 187.0.43.109:2694 SYN_RECV tcp 0 0 my.host.com:http 109.229.4.145:1722 SYN_RECV tcp 0 0 my.host.com:http 189-84-163-244.sodobr:63267 SYN_RECV tcp 0 0 my.host.com:http bd66839d.virtua.com.br:3469 SYN_RECV tcp 0 0 my.host.com:http 69.101.56.190.dsl.int:52552 SYN_RECV tcp 0 0 my.host.com:http pc-62-230-47-190.cm.vt:2262 SYN_RECV tcp 0 0 my.host.com:http 189-84-163-244.sodobr:63418 SYN_RECV tcp 0 0 my.host.com:http pc-62-230-47-190.cm.vt:1741 SYN_RECV tcp 0 0 my.host.com:http zaq3d739320.zaq.ne.jp:2141 SYN_RECV tcp 0 0 my.host.com:http netacc-gpn-4-80-73.po:52676 SYN_RECV tcpdump shows: 7:11:08.564510 IP 187-4-1xx-4.xxx.ipd.brasiltelecom.net.br.54821 my.host.com.http: S 999692166:999692166(0) win 65535 17:11:08.566347 IP 114-44-171-67.dynamic.hinet.net.1129 my.host.com.http: S 605369055:605369055(0) win 65535 17:11:08.570210 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5590 my.host.com.http: S 2813379182:2813379182(0) win 16384 17:11:08.571290 IP dsl-189-143-30-99-dyn.prod-infinitum.com.mx.1615 my.host.com.http: S 281542700:281542700(0) win 65535 17:11:08.583847 IP dsl-189-143-30-99-dyn.prod-infinitum.com.mx.1617 my.host.com.http: S 499413892:499413892(0) win 65535 17:11:08.588680 IP 170.51.229.112.2569 my.host.com.http: S 2195084898:2195084898(0) win 65535 17:11:08.588773 IP gw2-1.211.ru.3180 my.host.com.http: F 2315901786:2315901786(0) ack 2620913033 win 64240 17:11:08.590656 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5614 my.host.com.http: S 2813715032:2813715032(0) win 16384 17:11:08.591212 IP 203.82.82.54.15848 my.host.com.http: S 4070423507:4070423507(0) win 16384 17:11:08.591254 IP 203.82.82.54.2545 my.host.com.http: S 1790910784:1790910784(0) win 16384 17:11:08.591289 IP 203.82.82.54.28306 my.host.com.http: S 578615626:578615626(0) win 16384 17:11:08.591591 IP gw2-1.211.ru.3191 my.host.com.http: F 2316435991:2316435991(0) ack 2634205972 win 64240 17:11:08.591790 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5593 my.host.com.http: S 2813659017:2813659017(0) win 16384 17:11:08.593691 IP gw2-1.211.ru.3203 my.host.com.http: F 2316834420:2316834420(0) ack 2629074987 win 64240 I'm not sure what I can do to limit/mitigate this, currently no webpages are being served, any help gratefully appreciated.

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  • Wireshark vs Netmon for precise time tagging

    - by Nic
    I'm using Wireshark to time tag and get some statistics on multicast traffic. When there is not much traffic, the stats looks good, but as soon as there is a bunch of packets arriving at the same time, I have stats that are not even possible (e.g. round trip time of 0ms) I'm wondering if Netmon could be more precise in time tagging packet because it is not relying on the Winpcap driver? Does anybody already faced the same situation? Thanks a lot, Nic

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  • TCP connection stuck in SYN_RECV state despite ACK received, Linux 2.6.18, embedded, ARM

    - by waynix
    My client cannot connect to my protocol port (TCP) after some network glitches, even though all other protocols (telnet/HTTP/FTP) work fine. netstat shows that my server is listening and tcpdump on the server shows all 3 packets are exchanged: 18:29:16.578964 IP 10.9.59.10.3355 10.9.43.131.5084: S 2602965897:2602965897(0) win 65535 <mss 1460,nop,nop,sackOK> 18:29:16.579107 IP 10.9.43.131.5084 10.9.59.10.3355: S 3464857909:3464857909(0) ack 2602965898 win 5840 <mss 1460,nop,nop,sackOK> 18:29:16.579284 IP 10.9.59.10.3355 10.9.43.131.5084: . ack 1 win 65535 But somehow netstat -t shows the connection still in SYN_RECV, as if the ack is not seen by the TCP state machine. I have to restart my server to get it to work. syncookie is not enabled, and I know from client code behavior and tcpdump that there is no SYN flooding. Help much appreciated.

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  • "Must-have" Windows commandline tools?

    - by hvtuananh
    One commandline tool per answer :) WalkOnLAN This small command line utility makes possible to switch on a computer from a second one by sending a "Magic Packet". Both of computers can be located on the same LAN or on the different LAN segments. Anything else?

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