Ping Error Messages - Networking Computer Tips To block from ping respond #iptables –A INPUT –P icmp –icmp-type echo-request –j DROP Linux Iptables allow or block ICMP ping request The Internet Control Message Protocol (ICMP) has many messages that are identified by a "type" field. You need to use 0 and 8 ICMP code types. => Zero (0) is for echo-reply => Eight (8) is for echo-request. To enable ICMP ping incoming client request use following iptables rule (you need to add following rules to script). My default firewall policy is blocking everything. Task: Enable or allow ICMP ping incoming client request Rule to enable ICMP ping incoming client request ( assuming that default iptables policy is to drop all INPUT and OUTPUT packets) SERVER_IP="202.54.10.20" iptables -A INPUT -p icmp --icmp-type 8 -s 0/0 -d $SERVER_IP -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT iptables -A OUTPUT -p icmp --icmp-type 0 -s $SERVER_IP -d 0/0 -m state --state ESTABLISHED,RELATED -j ACCEPT Task: Allow or enable outgoing ping request To enable ICMP ping outgoing request use following iptables rule:
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Ping Error Messages - Networking Computer Tips
To block from ping respond
#iptables –A INPUT –P icmp –icmp-type echo-request –j DROP
Linux Iptables allow or block ICMP ping request
The Internet Control Message Protocol (ICMP) has many messages that are identified
by a "type" field. You need to use 0 and 8 ICMP code types.
=> Zero (0) is for echo-reply
=> Eight (8) is for echo-request.
To enable ICMP ping incoming client request use following iptables rule (you need to
add following rules to script).
My default firewall policy is blocking everything.
Task: Enable or allow ICMP ping incoming client request
Rule to enable ICMP ping incoming client request ( assuming that default iptables policy
PING (Packet Internet Groper) is a program used to test whether a particular network host is online by sending an ICMP (Internet control message protocol) echo request and waiting for a response. It is used for troubleshooting connectivity between network devices such as servers, routers, workstations and printers
TTL Expired in TransitThe TTL value determines the maximum amount of time an IP packet may live in the network without reaching its destination. It is effectively a bound on the number of routers an IP packet may pass through before being discarded. This message indicates that the TTL expired in transit. Number of required hops exceeds TTL. Increase TTL by using the ping -i switch.
Destination Host UnreachableThe host that you are trying to ping is down or is not operating on the network. A local or remote route does not exist for destination host. Modify the local route table or notify the router administrator.
Request Timed OutThe ping command timed out because there was no reply from the host. No Echo Reply messages were received due to network traffic, failure of the ARP request packet filtering, or router error. Increase the wait time using the ping -w switch.
Unknown HostThe IP Address or the Host Name does not exist in the network or the destination host name cannot be resolved. Verify name and availability of DNS servers.
TTL Expired in Transit
The number of hops required to reach the destination exceeds the TTL set by the sending host to forward the packets. The default TTL value for ICMP Echo Requests sent by Ping is 32. In some cases, this is not enough to travel the required number of links to a destination. You can increase the TTL using the -i switch, up to a maximum of 255 links.
If increasing the TTL value fails to resolve the problem, the packets are being forwarded in a routing loop, a circular path among routers. Use Tracert to track down the source of the routing loop, which appears as a repeated series of the same IP addresses in the Tracert report. Next, make an appropriate change to the routing tables, or inform the administrator of a remote router of the problem.
Top Of Page
Destination Host Unreachable
This message indicates one of two problems: either the local system has no route to the desired destination, or a remote router reports that it has no route to the destination. The two problems can be distinguished by the form of the message. If the message is simply "Destination Host Unreachable," then there is no route from the local system, and the packets to be sent were never put on the wire. Use the Route utility to check the local routing table.
If the message is "Reply From < IP address >: Destination Host Unreachable," then the routing problem occurred at a remote router, whose address is indicated by the "< IP address >" field. Use the appropriate utility or facility to check the IP routing table of the router assigned the IP address of < IP address >.
If you pinged using an IP address, retry it with a host name to ensure that the IP address you tried is correct.
Request Timed Out
This message indicates that no Echo Reply messages were received within the default time of 1 second. This can be due to many different causes; the most common include network congestion, failure of the ARP request, packet filtering, routing error, or a silent discard. Most often, it means that a route back to the sending host has failed. This might be because the
destination host does not know the route back to the sending host, or one of the intermediary routers does not know the route back, or even that the destination host's default gateway does not know the route back. Check the routing table of the destination host to see whether it has a route to the sending host before checking tables at the routers.
If the remote routing tables are correct and contain a valid route back to the sending host, to see if the ARP cache lacks the proper address, use the arp -acommand to print the contents of the ARP cache. Also, check the subnet mask to be sure that a remote address has not been interpreted as local.
Next, use Tracert to follow the route to the destination. While Tracert does not record the address of the last hop or the path that the packet followed on the return path, it might show that the packet made it to the destination. If this is the case, the problem is probably a routing issue on the return path. If the trace doesn't quite reach the destination, it might be because the target host is protected by a firewall. When a firewall protects the destination, ICMP packet filtering prevents the ping packets—or any other ICMP messages—from crossing the firewall and reaching their destination.
To check for network congestion, simply increase the allowed latency by setting a higher wait time with the -w switch, such as 5000 milliseconds. Try to ping the destination again. If the request still times out, congestion is not the problem; an address resolution problem or routing error is a more likely issue.
Unknown Host
This error message indicates that the requested host name cannot be resolved to its IP address; check that the name is entered correctly and that the DNS servers can resolve it.
Code Description
0 Network unreachable error.
1 Host unreachable error.
2 Protocol unreachable error (the designated transport protocol is not supported).
3Port unreachable error (the designated protocol is unable to inform the host of the incoming message).
4The datagram is too big. Packet fragmentation is required but the 'don't fragment' (DF) flag is on.
5 Source route failed error.
6 Destination network unknown error.
7 Destination host unknown error.
8 Source host isolated error (military use only).
9 The destination network is administratively prohibited.
10 The destination host is administratively prohibited.
11 The network is unreachable for Type Of Service.
12 The host is unreachable for Type Of Service.
13Communication administratively prohibited (administrative filtering prevents packet from being forwarded).
14Host precedence violation (indicates the requested precedence is not permitted for the combination of host or network and port).
15Precedence cutoff in effect (precedence of datagram is below the level set by the network administrators).
The default TTL value for ICMP Echo Requests sent by Ping is 32.
Difference in Hub, Switch, Bridge, & Router | Nutt.net
www.nutt.net
In an ethernet network there are 4 devices that from the the outside look very similar. In this article we will look at the difference between hubs, switches, bridges, and routers.
Top of Form
Like · · Follow Post · Share · 7 hours ago near Chennai
Muthu Kumaran Loganathan Hub: 1) Unintelligent Device 2) No Technology to handle MAC information 3) No memory 4) It gets the data from one port, regenerates the data and sends the data to all ports. 5) Also called as multi port Repeater.
2 hours ago · Like
Muthu Kumaran Loganathan Switch: 1) Intelligent Device 2) It has RAM to handle MAC information 3) It forwards the data with the help of MAT(MAC Address Table) 4) It has a specialized hardware called ASICS (Application Specific Integrated Circuits)
2 hours ago · Like
Muthu Kumaran Loganathan Router: 1) Used to communicate between different Networks. 2) It provides WAN Connectivity 3) It can read IP Header information. 4) It maintains IP routing table which contains best paths to reach destination networks.
2 hours ago · Like
Bottom of Form
/windows/system32/drivers/etc/hosts file...
2 hours ago · Like
The proxy is not applied in the above scenario.. that's the question... So we need to check in the Hosts file... EX: If you give 127.0.0.1 yahoo.com, it will assign that yahoo.com ip is 127.0.0.1, but it is a loop back ip.. so You can't able