1
vote
2answers
40 views

with fully permissive iptables, tcpdump shows icmp echo requests arriving, but no reply's are sent

I'm a bit stumped on where to look next. When using SoftEther IPsec VPN into my network, I can access every server in the main subnet but one. When behind the main firewall, the server responds to all ...
-4
votes
2answers
46 views

How to manage PING replies? [closed]

How can I manage, for example, my Ubuntu mashine so it doesn't (or does) respond to PING(ICMP ECHO_REQUEST - type 8) requests? Normally almost all computers in a LAN network responds to ping with an ...
1
vote
0answers
99 views

Linux MIPS box: ICMP (ping) works, but TCP does not - how to fix it?

I'm trying to set up MIPS Linux box network. Here is it's configuration: ~ # ifconfig eth0 Link encap:Ethernet HWaddr CC:5D:4E:FF:45:7F inet addr:192.168.0.2 Bcast:192.168.0.255 ...
2
votes
3answers
208 views

What is the “right way” to monitor network?

My production servers are kept at US east coast and some of the supporting apps are kept at Amsterdam in Europe. There is a Nagios instance running at US east coast as well which does a few port ...
0
votes
1answer
73 views

How can I proxy ICMP requests?

I have a ubuntu server that receives many ping requests from various other servers in the network. I would like to be able to proxy these requests. Using iptable rules I can see how to DROP or ACCEPT ...
1
vote
2answers
139 views

ICMP and traceroute , How does ICMP keep a counter while it passess hops

When tracerouting a destination and going through all these hops, what happens during this process? Does ICMP have an initial counter and decrements this counter on each hop it passes? If the counter ...
0
votes
2answers
384 views

Test a server using MTR through TCP

Is it possible to use MTR over TCP? If not is there an alternative? I have done some research and I am not finding any way to do such a thing, so I'm wondering if anyone has had any experience with ...
0
votes
0answers
191 views

What does given filed mean in netstat -s on Linux

I am analyzing the the output of netstat -s and wanted to know what "input ICMP message failed" is meant for ,below is output of netstat -s Icmp: 643 ICMP messages received 0 input ICMP ...
-4
votes
1answer
395 views

How can I stop Linux from sending ICMP “Destination Unreachable” responses? [closed]

I have a Linux system which has a number of services disabled (for example, telnet). When a telnet client attempts a connection, the system responds with an ICMP "Destination Unreachable". Is there ...
0
votes
2answers
433 views

Is there a good reason for ICMP to be called a layer 3 protocol? [closed]

ICMP is categorized as a layer 3 protocol in the osi model, but as far as i can tell it does not meet the definition of a network layer protocol. It does not provide addressing or packet routing (it ...
0
votes
2answers
2k views

Fragmentation and packet size,using tcpdump

i am trying to understand concept of fragmentation: i have two virtual machines with public ip connected to a switch. tracepath shows packet not going through gateway from vm1: Trying to send ...
0
votes
1answer
72 views

Why are there two types of ICMP Redirect?

Wikipedia lists 4 types of ICMP Redirect reasons: 0 Redirect for Network 1 Redirect for Host 2 Redirect for Type of Service and Network 3 Redirect for Type of Service and Host I understand ...
4
votes
1answer
195 views

tcpdump on interface when pinging nonexistent hosts on local network

I've statically configured the IP address of an interface on a server: ip addr add 10.40.0.6/16 broadcast 10.40.255.255 dev eth1 If I try to ping a machine on the network (e.g., 10.40.0.1), it ...
2
votes
2answers
1k views

Can't ping multihoned Linux machine on non-default interface

I have a multihoned Ubuntu server with a set of interfaces that includes: eth2: 10.10.0.131/24 eth3: 10.20.0.2/24 The default interface is eth2, with a gateway of 10.10.0.1. Here's what the routing ...
4
votes
7answers
684 views

Scan for connected, powered on computers on a network?

I want to scan for powered on computers on my LAN and gather logs about that. I tried nmap but it didn't work very well (a lot of switched on computers are not getting detected). nmap -sP ...
0
votes
1answer
174 views

Ubuntu stops responding to ping from random clients

I got a ubuntu server running redmine from apache. My clients, can access redmine, but stops responding random, and other clients, can browse redmine fine, when the client with the problem cant ...
1
vote
0answers
726 views

Why is my CentOS box rejecting some (but not all) ICMP ping requests from the same remote host?

CentOS 4.x I've got several old CentOS 4.x systems and have configured iptables to allow ICMP traffic. Originally, I had an iptables rule that looked like: -A RH-Firewall-1-INPUT -p icmp ...
2
votes
1answer
277 views

Can i stop tcp handshake by send icmp of unreachable host

This is what happened: client - send syn server - send icmp (unreachable host [i also try to add code =10] ) wait for 100 ms send syn-ack client - send ack in response to the ...
3
votes
1answer
259 views

How does the ping command differentiate between its ICMP responses and anothers?

If I have two shells open each pinging the same host, how do the two shells differentiate between the ICMP responses coming back for each shell?
7
votes
2answers
6k views

Why do ICMP Redirect Host happen?

I'm setting up a Debian box as a router for 4 subnets. For that I have defined 4 virtual interfaces on the NIC where the LAN is connected (eth1). eth1 Link encap:Ethernet HWaddr ...
0
votes
2answers
1k views

freebsd dmesg has a lot of “Limiting icmp unreach response from 1293 to 200 packets/sec”

I has a simple freebsd 9.0 machine.But everytime i start my freebsd and use command dmesg. There aren't any hardware information there but full of "Limiting icmp unreach response from 1293 ...
4
votes
3answers
5k views

Denying ICMP type 3 code 4 traffic - good or bad?

Investigating a slow VPN connection (Cisco ASA IPSec) to a remote office, I noticed on our firewall a lot of access rule matches: Denied ICMP type=3, code=4 from *ip_address* on interface outside I ...
1
vote
1answer
7k views

What causes duplicate ICMP ECHO responses?

I've never seen this before, neither have a colleague and an ex-colleague, both with a reasonably strong background in smallish ISP operations. What causes so many duplicate ICMP ECHO responses? $ ...
5
votes
2answers
1k views

iptables | Types of ICMP: which ones are (potentially) harmful?

I read that certain types┬╣ of ICMP packets can be harmful. Questions: Which ones and why? How should I layout an iptables ruleset to handle each type of ICMP packet? Should I rate-limit any of these ...
1
vote
1answer
383 views

Linux router - how to send icmp unreachable messages to LAN clients

I have a Linux home router with eth0 (192.168.0.2/24) and bridge br0 for LAN clients (192.168.1.1/24). Bridge br0 contains eth1 (wired) and eth2 (wireless). The router routes all LAN traffic via eth0 ...
2
votes
1answer
681 views

Wireshark Display Filtered for Unreplied ICMP Echo Packets

Is there a wireshark display filter that will find ICMP echo requests that didn't have a reply?
0
votes
1answer
89 views

execute command on icmp request

I'd like to know how/if it is possible to get my linux (ubuntu) box to exec a command (script) on incoming icmp/ping (or other network events) requests? Like e.g. playing a "ping" sound when being ...
1
vote
2answers
691 views

Pinging same address multiple times

I am just wondering if it is possible to ping the same ip address from the same source multiple times (ie fast enough so they get pipelined) and still get a valid result. By a valid result, I mean ...
1
vote
1answer
3k views

Why is network stack ignoring icmp replies from non-default interface?

I have following situation: eth0 - default gateway ( ip: 172.28.183.100, gw: 172.28.183.1 ) eth0 - secondary network connection ( ip: 172.28.171.2, gw: 172.28.171.2). routing looks like this: ...
3
votes
3answers
3k views

ping -f shows problems but regular ping doesn't

I have a strange issue, hosting at Softlayer Washington data center. Test from an EC2 instance to my server at Softlayer :- [root@EC2-box ~]# ping -f -c 100 MY-SL-BOX PING MY-SL-BOX (MY-SL-BOX) ...
2
votes
8answers
2k views

Ping command is not accepted if firewall is on at remote system

I am using ping command to know whether remote machine is on or not. But problem is that ping command (ICMP Packect) is not accepted at remote machine if firewall is on and it assumed that remote ...
1
vote
7answers
4k views

Server with slow ping response

Two boxes with identical loads serving the same sites tend to slow down and stop responding to ping. The slow (or intermittent) ping causes our load balancer to think the servers are offline and ...