Upload
vijay-ruban
View
203
Download
0
Embed Size (px)
Citation preview
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:
SERVER_IP="202.54.10.20"
iptables -A OUTPUT -p icmp --icmp-type 8 -s $SERVER_IP -d 0/0 -m
state --state NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p icmp --icmp-type 0 -s 0/0 -d $SERVER_IP -m
state --state ESTABLISHED,RELATED -j ACCEPT
How do I disable outgoing ICMP request?
Use the following rules:
iptables -A OUTPUT -p icmp --icmp-type echo-request -j DROP
OR
iptables -A OUTPUT -p icmp --icmp-type 8 -j DROP
ICMP echo-request type will be block by above rule.
See ICMP TYPE NUMBERS (type fields). You can also get list of ICMP types, just type
following command at shell prompt:
# /sbin/iptables -p icmp -h
ShareThis
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.
OS/Device Version Protocol TTL
AIX TCP 60
AIX UDP 30
AIX 3.2, 4.1 ICMP 255
BSDI BSD/OS 3.1 and 4.0 ICMP 255
Compa Tru64 v5.0 ICMP 64
Cisco ICMP 254
DEC Pathworks V5 TCP and UDP 30
Foundry ICMP 64
FreeBSD 2.1R TCP and UDP 64
FreeBSD 3.4, 4.0 ICMP 255
FreeBSD 5 ICMP 64
HP-UX 9.0x TCP and UDP 30
HP-UX 10.01 TCP and UDP 64
HP-UX 10.2 ICMP 255
HP-UX 11 ICMP 255
HP-UX 11 TCP 64
Irix 5.3 TCP and UDP 60
Irix 6.x TCP and UDP 60
Irix 6.5.3, 6.5.8 ICMP 255
juniper ICMP 64
MPE/IX (HP) ICMP 200
Linux 2.0.x kernel ICMP 64
Linux 2.2.14 kernel ICMP 255
Linux 2.4 kernel ICMP 255
Linux Red Hat 9 ICMP and TCP 64
MacOS/MacTCP 2.0.x TCP and UDP 60
MacOS/MacTCP X (10.5.6) ICMP/TCP/UDP64
NetBSD ICMP 255
Netgear FVG318 ICMP and UDP 64
OpenBSD 2.6 & 2.7 ICMP 255
OpenVMS 07.01.2002 ICMP 255
OS/2 TCP/IP 3.0 64
OSF/1 V3.2A TCP 60
OSF/1 V3.2A UDP 30
Solaris 2.5.1, 2.6, 2.7, 2.8 ICMP 255
Solaris 2.8 TCP 64
Stratus TCP_OS ICMP 255
Stratus TCP_OS (14.2-) TCP and UDP 30
Stratus TCP_OS (14.3+) TCP and UDP 64
Stratus STCP ICMP/TCP/UDP60
SunOS 4.1.3/4.1.4 TCP and UDP 60
SunOS 5.7 ICMP and TCP 255
Ultrix V4.1/V4.2A TCP 60
Ultrix V4.1/V4.2A UDP 30
Ultrix V4.2 – 4.5 ICMP 255
VMS/Multinet TCP and UDP 64
VMS/TCPware TCP 60
VMS/TCPware UDP 64
VMS/Wollongong 1.1.1.1 TCP 128
VMS/Wollongong 1.1.1.1 UDP 30
VMS/UCX TCP and UDP 128
Windows for Workgroups TCP and UDP 32
Windows 95 TCP and UDP 32
Windows 98 ICMP 32
Windows 98, 98 SE ICMP 128
Windows 98 TCP 128
Windows NT 3.51 TCP and UDP 32
Windows NT 4.0 TCP and UDP 128
Windows NT 4.0 SP5- 32
Windows NT 4.0 SP6+ 128
WindowsNT 4 WRKS SP 3, SP 6a
ICMP 128
Windows NT 4 Server SP4 ICMP 128
Windows ME ICMP 128
Windows 2000 pro ICMP/TCP/UDP128
Windows 2000 family ICMP 128
Windows Server 2003 128
Windows XP ICMP/TCP/UDP128
.
7. Application Layer
NNTP · SIP · SSI · DNS · FTP ·Gopher · HT
TP · NFS · NTP · SMPP ·SMTP · SNMP · Te
lnet · DHCP ·Netconf · RTP · SPDY · (more)
6. Presentation Layer
MIME · XDR · TLS · SSL
5. Session Layer
Named Pipes · NetBIOS · SAP · L2TP · PPTP · SOCKS
4. Transport Layer
TCP · UDP · SCTP · DCCP · SPX
3. Network Layer
IP (IPv4, IPv6) · ICMP · IPsec · IGMP ·IPX · AppleTalk
2. Data Link Layer
ATM · SDLC · HDLC · ARP · CSLIP ·SLIP · GFP · PLIP · IEEE 802.3 ·Frame Relay · ITU
-T G.hn DLL · PPP ·X.25 · Network Switch ·
1. Physical Layer
EIA/TIA-232 · EIA/TIA-449 · ITU-T V-Series · I.430 · I.431 · POTS · PDH ·SONET/SDH · PON · OTN · DSL ·IEEE 802.3 · IEEE 802.11
·IEEE 802.15 · IEEE 802.16 · IEEE 1394 · ITU
-T G.hn PHY · USB · Bluetooth ·Hubs
o Access… Run Command
Accessibility Controls access.cpl
Accessibility Wizard accwiz
Add Hardware Wizard hdwwiz.cpl
Add/Remove Programs appwiz.cpl
Administrative Toolscontrol admintools
Adobe Acrobat (if installed) acrobat
Adobe Designer (if installed) formdesigner
Adobe Distiller (if installed) acrodist
Adobe ImageReady (if installed) imageready
Adobe Photoshop (if installed) photoshop
Automatic Updates wuaucpl.cpl
Bluetooth Transfer Wizard fsquirt
Calculator calc
Certificate Manager certmgr.msc
Character Map charmap
Check Disk Utility chkdsk
Clipboard Viewer clipbrd
Command Prompt cmd
Component Services dcomcnfg
Computer Management compmgmt.msc
Control Panel control
Date and Time Properties timedate.cpl
DDE Shares ddeshare
Device Manager devmgmt.msc
Direct X Control Panel (if installed)* directx.cpl
Direct X Troubleshooter dxdiag
Disk Cleanup Utility cleanmgr
Disk Defragment dfrg.msc
Disk Management diskmgmt.msc
Disk Partition Manager diskpart
Display Properties control desktop
Display Properties desk.cpl
Display Properties (w/Appearance Tab Preselected) control color
Dr. Watson System Troubleshooting Utility drwtsn32
Driver Verifier Utility verifier
Event Viewer eventvwr.msc
Files and Settings Transfer Tool migwiz
File Signature Verification Tool sigverif
Findfast findfast.cpl
Firefox (if installed) firefox
Folders Properties folders
Fonts control fonts
Fonts Folder fonts
Free Cell Card Game freecell
Game Controllers joy.cpl
Group Policy Editor (XP Prof) gpedit.msc
Hearts Card Game mshearts
Help and Support helpctr
HyperTerminal hypertrm
Iexpress Wizard iexpress
Indexing Service ciadv.msc
Internet Connection Wizard icwconn1
Internet Explorer iexplore
Internet Properties inetcpl.cpl
Internet Setup Wizard inetwiz
IP Configuration (Display Connection Configuration) ipconfig /all
IP Configuration (Display DNS Cache Contents)ipconfig /displaydns
IP Configuration (Delete DNS Cache Contents)ipconfig /flushdns
IP Configuration (Release All Connections) ipconfig /release
IP Configuration (Renew All Connections) ipconfig /renew
IP Configuration (Refreshes DHCP & Re-Registers DNS)ipconfig /registerdns
IP Configuration (Display DHCP Class ID)ipconfig /showclassid
IP Configuration (Modifies DHCP Class ID)ipconfig /setclassid
Java Control Panel (if installed) jpicpl32.cpl
Java Control Panel (if installed) javaws
Keyboard Properties control keyboard
Local Security Settings secpol.msc
Local Users and Groups lusrmgr.msc
Logs You Out Of Windows logoff
Malicious Software Removal Tool mrt
Microsoft Access (if installed) msaccess
Microsoft Chat winchat
Microsoft Excel (if installed) excel
Microsoft Frontpage (if installed) frontpg
Microsoft Movie Maker moviemk
Microsoft Paint mspaint
Microsoft Powerpoint (if installed) powerpnt
Microsoft Word (if installed) winword
Microsoft Syncronization Tool mobsync
Minesweeper Game winmine
Mouse Properties control mouse
Mouse Properties main.cpl
Nero (if installed) nero
Netmeeting conf
Network Connectionscontrol netconnections
Network Connections ncpa.cpl
Network Setup Wizard netsetup.cpl
Notepad notepad
Nview Desktop Manager (if installed) nvtuicpl.cpl
Object Packager packager
ODBC Data Source Administrator odbccp32.cpl
On Screen Keyboard osk
Opens AC3 Filter (if installed) ac3filter.cpl
Outlook Express msimn
Paint pbrush
Password Properties password.cpl
Performance Monitor perfmon.msc
Performance Monitor perfmon
Phone and Modem Options telephon.cpl
Phone Dialer dialer
Pinball Game pinball
Power Configuration powercfg.cpl
Printers and Faxes control printers
Printers Folder printers
Private Character Editor eudcedit
Quicktime (If Installed) QuickTime.cpl
Quicktime Player (if installed) quicktimeplayer
Real Player (if installed) realplay
Regional Settings intl.cpl
Registry Editor regedit
Registry Editor regedit32
Remote Access Phonebook rasphone
Remote Desktop mstsc
Removable Storage ntmsmgr.msc
Removable Storage Operator Requests ntmsoprq.msc
Resultant Set of Policy (XP Prof) rsop.msc
Scanners and Cameras sticpl.cpl
Scheduled Taskscontrol schedtasks
Security Center wscui.cpl
Services services.msc
Shared Folders fsmgmt.msc
Shuts Down Windows shutdown
Sounds and Audio mmsys.cpl
Spider Solitare Card Game spider
SQL Client Configuration cliconfg
System Configuration Editor sysedit
System Configuration Utility msconfig
System File Checker Utility (Scan Immediately) sfc /scannow
System File Checker Utility (Scan Once At The Next Boot) sfc /scanonce
System File Checker Utility (Scan On Every Boot) sfc /scanboot
System File Checker Utility (Return Scan Setting To Default) sfc /revert
System File Checker Utility (Purge File Cache) sfc /purgecache
System File Checker Utility (Sets Cache Size to size x) sfc /cachesize=x
System Information msinfo32
System Properties sysdm.cpl
Task Manager taskmgr
TCP Tester tcptest
Telnet Client telnet
Tweak UI (if installed) tweakui
User Account Management nusrmgr.cpl
Utility Manager utilman
Windows Address Book wab
Windows Address Book Import Utility wabmig
Windows Backup Utility (if installed) ntbackup
Windows Explorer explorer
Windows Firewall firewall.cpl
Windows Magnifier magnify
Windows Management Infrastructure wmimgmt.msc
Windows Media Player wmplayer
Windows Messenger msmsgs
Windows Picture Import Wizard (need camera connected) wiaacmgr
Windows System Security Tool syskey
Windows Update Launches wupdmgr
Windows Version (to show which version of windows) winver
Windows XP Tour Wizard tourstart
Wordpad write
diff b/w hub,switch,bridge,router
http://www.nutt.net/2004/11/20/difference-in-hub-switch-bridge-router/
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
II.ROUTING PROTOCOLS
Most of the routing algorithms they are possible to be classified like one of two basic algorithms:
Distance Vector and Link-State.
1. Distance Vector characteristics: 3
(1 collects data of the information of the routing table of its neighbors.
(2) determines the best route adding the metric value that receives
as the routing information happens from router to another one.
(3) With most of the protocols of routing by distance vector, the updates for the changes of
topology consist of periodic updates of the tables.
RIP and EIGRP are examples of vector distance protocols.
2. Link state characteristics:
(1) The link state routing obtains a great vision of the topology of complete internetwork
accumulating all the necessary LSA.
(2) In the link state routing, each router it works independently to calculate its own shorter route
towards the networks destiny.
(3) With the protocols of routing of connection state, the updates are caused generally by
changes in the topology. The relatively small LSA that have gone to all the others routers
generally give like result faster times of convergence with any change of topology of the
internetwork.
OSPF it’s an example of link state protocol.
A. Routing information protocol (RIP)
d. RIP characteristics:
(1) Distance vector routing protocol.
(2) It metric is the number of jumps.
(3) The maximum number of jumps is 15 4
(4) One updates every 30 seconds
(5) Not always it selects the fastest route for the packages
(6) It generates great amount of traffic of network with updates.
Another one of the problems that the use of the RIP presents is that sometimes a destiny can be
located too much far like being attainable. The RIP allows fifteen as maximum limit for the
number of jumps through which data can be sent. The network destiny is considered unreachable
if there are more than fifteen jumps of router.
B. Enhanced Interior Gateway Routing Protocol (EIGRP)
As its name suggests, EIGRP is an enhanced version of IGRP (Interior Gateway Routing
Protocol), an obsolete routing protocol that was developed by Cisco
EIGRP sends partial updates
when a metric or the topology on the network changes. It does not send full routing-table updates
in periodic fashion as distance-vector protocols do. EIGRP is a classless protocol that permits the
use of VLSMs (Variable Length Subnet Masks) and supports CIDR (Classless Inter-Domain
Routing) for a scalable allocation of IP addresses.
EIGRP uses the metrics like bandwidth, delay, reliability, load, and MTU in making its routing
decisions .The default metrics used are bandwidth and delay. For a more granular level of control,
EIGRP multiplies each of the metrics by 256 before performing the calculation of the composite
metric. EIGRP has been designed to make much better use of bandwidth, and to allow routers to
have a much better awareness of neighboring routers. Instead of sending its entire routing table
out at regular intervals, an EIGRP router sends out only partial updates, and even then, only
when a route changes. This makes a better use of the available network bandwidth. An EIGRP
router also has a more complete view of the network than a typical distance vector protocol as it
not only maintains its own routing table, but also keeps a copy of the routing tables of
neighboring routers. When an EIGRP router cannot find a route to a network based on all the
information it currently has, it sends out a query to other routers, which is propagated until a
route is found.
C. Open shortest path first (OSPF)
(1) Fast detection of changes in the topology and very fast reestablishment of routes without
loops.
(2) Low overload, use updates that inform about changes on routes.
(3) Division of traffic by several equivalent routes.
(4) Routing according type of service.
(5) Use of multi-send in local area networks.
(6) Subnet and Super-net mask.
(7) Authentication
III. SIMULATION
1. Simulation Methodology
Network is simulated using OPNET® Modeler. OPNET®