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Topic: Destination Unreachable

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	[No title]
		Destination Address The address of the gateway or host to which the message should be sent.
		Description If, according to the information in the gateway's routing tables, the network specified in the internet destination field of a datagram is unreachable, e.g., the distance to the network is infinity, the gateway may send a destination unreachable message to the internet source host of the datagram.
		If, in the destination host, the IP module cannot deliver the datagram because the indicated protocol module or process port is not active, the destination host may send a destination unreachable message to the source host.
	www.ietf.org /rfc/rfc0792.txt (3481 words)

	ICMP type 3, Destination unreachable message
		A Destination Unreachable message that is received with code 0 (Net), 1 (Host), or 5 (Bad Source Route) may result from a routing transient and MUST therefore be interpreted as only a hint, not proof, that the specified destination is unreachable.
		The ICMP Destination Unreachable message is sent by a router in response to a packet which it cannot forward because the destination (or next hop) is unreachable or a service is unavailable.
		Routers MUST use Host Unreachable or Destination Host Unknown codes whenever other hosts on the same destination network might be reachable; otherwise, the source host may erroneously conclude that all hosts on the network are unreachable, and that may not be the case.
	www.networksorcery.com /enp/protocol/icmp/msg3.htm (2097 words)

	[No title] (Site not responding. Last check: 2007-10-30)
		Route Reply Generation by the Destination If the generating node is the destination itself, it uses a destination sequence number at least equal to a sequence number generated after the last detected change in its neighbor set and at least equal to the destination sequence number in the RREQ.
		For cases (i) and (ii), the destination sequence numbers in the routing table for the unreachable destination(s) are incremented by one.
		For case (iii) when a node receives a RERR message, for each unreachable destination included in the packet, the node determines whether the source node (as indicated by the source IP address in the IP header) forwarding the RERR packet is its own next hop used to reach this destination.
	www.cis.upenn.edu /group/verinet/references/AODVv8.txt (7497 words)

	ICMPv6: New destination unreachable codes (Site not responding. Last check: 2007-10-30)
		Description A Destination Unreachable message SHOULD be generated by a router, or by the IPv6 layer in the originating node, in response to a packet that cannot be delivered to its destination address for reasons other than congestion.
		One specific case in which a Destination Unreachable message with a code 3 is sent is in response to a packet received by a router from a point-to-point link, destined to an address within a subnet assigned to that same link (other than one of the receiving router's own addresses).
		A destination node SHOULD send a Destination Unreachable message with Code 4 in response to a packet for which the transport protocol (e.g., UDP) has no listener, if that transport protocol has no alternative means to inform the sender.
	www.mail-archive.com /ipv6@ietf.org/msg01420.html (523 words)

	[No title]
		Once the encapsulated datagram arrives at this intermediate destination node, it is decapsulated, yielding the original IP datagram, which is then delivered to the destination indicated by the original Destination Address field.
		Destination Unreachable (Type 3) ICMP Destination Unreachable messages are handled by the encapsulator depending upon their Code field.
		In particular, the original values of the Source Address, Destination Address, and Protocol fields in the IP header, and the port numbers used in any transport header within the datagram, are not located in their normal positions within the datagram after encapsulation.
	www.isi.edu /in-notes/rfc2003.txt (3719 words)

	ICMP Ping Message Types and Traceroute Codes for ICMP Type 3
		Destination UDP port should be chose as an unlikely value, so that it is impossible that any destination application uses this port.
		If router cannot forward the packet because no route to the destination and the packet has a TOS that is either equal to the TOS requested in the packet or is the default TOS (0000) then the router generates the message host unreachable for TOS (type 3, code 12).
		But destination port is chose as unlikely value, so that destination UDP module generates an ICMP message port unreachable.
	users.lmi.net /canepa/subdir/icmp.html (440 words)

	Network Layer/Internet Protocols > ICMP Message Types (Site not responding. Last check: 2007-10-30)
		Destination Unreachable uses several code values to further describe the function of the ICMP message being sent.
		When a client attempts to connect to a host on a network that is unreachable, a gateway generates this message to alert the source host of the problem.
		A port unreachable message indicates that the process or application the source host is attempting to establish a connection with is not active on the destination host.
	www.samspublishing.com /articles/article.asp?p=26557&seqNum=5 (3026 words)

	RFC 0777 - Introduction
		Description If, according to the information in the gateway's routing tables, the network specified in the internet destination field of a datagram is unreachable, e.g., the distance to the network is infinity, the gateway sends a destination unreachable message to [Page 3]
		In this case the gateway must discard the datagram and return a destination unreachable message.
		April 1981 RFC 777 The gateway or host may send the source quench message when it approaches its capacity limit rather than waiting until the capacity is exceeded.
	www.muonics.com /rfc/rfc777.php (2319 words)

	Sustainable Softworks - IPNetMonitor \| Reviewer Guide
		When pinging a remote host, it is possible an intermediate router will respond that the destination is unreachable and give a reason code.
		An orange "X" indicates an ICMP destination unreachable response was received.
		The destination unreachable "reason" is given in the log window.
	www.sustworks.com /site/ipm_revguide/ping_unreachable.html (171 words)

	Scenario 3: Configuring a Clustered Route (Site not responding. Last check: 2007-10-30)
		If a destination is found to be unreachable, it is removed from the cluster for the specified number of seconds.
		If all unavailable destinations are still unavailable, it will attempt all currently unreachable destinations in turn on the off-chance that one has become available.
		In fact, if there is one unreachable destination, an unreachable type fault is returned, because it is always the last "type" destination to be tried.
	www.capeclear.com /support/manuals/cc47/help/mergedProjects/Reference/parti/router_scenarios/scenario_3__configuring_a_clustered_route.htm (906 words)

	The TCP/IP Guide - ICMPv6 Destination Unreachable Messages
		The destination port specified in the UDP or TCP header was invalid or does not exist on the destination host.
		Also, Destination Unreachable messages are only sent when there is a fundamental problem with delivering a particular datagram; they are not sent when a datagram is dropped simply due to congestion of a router.
		Key Concept: ICMPv6 Destination Unreachable messages are used in the same manner as the ICMPv4 message of that name: to inform a sending device of a failure to deliver an IP datagram.
	www.tcpipguide.com /free/t_ICMPv6DestinationUnreachableMessages-3.htm (594 words)

	57. Internet Control Message Protocol
		The Destination Unreachable message is sent by a router (gateway) or a host when the destination network or service is not available.
		A destination host may reply with a Destination Unreachable message when the service (port or protocol) is not currently active.
		A router may reply with a Destination Unreachable message when its entry for the destination network is unreachable (set to infinity) or if the IP datagram Don't Fragment flag is set on and the router must fragment it in order to forward it.
	www.techbooksforfree.com /intro_to_data_com/page253.html (2157 words)

	Cisco - Using the traceroute Command on Operating Systems
		The destination UDP port of the initial datagram probe is set to 33434 (or as specified in the extended traceroute command output).
		The UDP destination port is incremented, the source UDP port is randomized, and the second datagram dispatched.
		A "host unreachable," "net unreachable," "maximum TTL exceeded," or a "timeout" type of message, which means that the probe is resent.
	www.cisco.com /warp/public/105/traceroute.shtml (2311 words)

	[No title] (Site not responding. Last check: 2007-10-30)
		If the gateway's routing tables consider the destination network unreachable, then the gateway will send a destination unreachable message to the source of the datagram.
		If the gateway can determine that the destination host itself is unreachable, then the gateway may also send this message.
		The code field is used to provide a more specific reason as to why the destination was considered unreachable.
	www.camtp.uni-mb.si /books/Internet-Book/ICMP_DestUnreach.html (509 words)

	[No title]
		The set may be empty (if the destination is unreachable), or it may contain one or more routes to the destination.
		If, however, a route to the destination exists which has a different TOS value and a non-infinite metric then code 11 (Network unreachable for type of service) or code 12 (Host unreachable for type of service) must be used instead.
		B.5 The Use of Destination Unreachable Perhaps the most contentious and least defensible part of this specification is that a packet can be discarded because the destination is considered to be unreachable even though a packet to the same destination but requesting a different TOS would have been deliverable.
	www.isi.edu /in-notes/rfc1349.txt (8474 words)

	The Elder Geek on Windows XP > Ping = Destination Net Unreachable ! (Site not responding. Last check: 2007-10-30)
		The three 255's mean that any packet sent out from a PC (call it X) in which the first three groups of the destination match the IP address of X, the destination is presumed to be local and is sent directly.
		In this case, the packet is not sent to the destination directly.
		Instead, it is sent to the default gateway with a tag informing the remote gateway of the final destination.
	www.theeldergeek.com /forum/lofiversion/index.php/t10889.html (869 words)

	4.9 What are all these ``ICMP destination unreachable'' alerts?
		The ICMP Destination Unreachable (message type 3) is sent back to the originator when an IP packet could not be delivered to the destination address.
		ICMP Port Unreachable - the destination port on the targeted host is closed (a.k.a.
		ICMP Protocol Unreachable - the protocol we were trying to use is not being used on the targeted host.
	www.snort.org /docs/faq/1Q05/node61.html (365 words)

	RE: ICMPv6: New destination unreachable codes (Site not responding. Last check: 2007-10-30)
		> Description > > A Destination Unreachable message SHOULD be generated by a router, or > by the IPv6 layer in the originating node, in response to a packet > that cannot be delivered to its destination address for reasons other > than congestion.
		The > example of such cases are inability to resolve the IPv6 destination > address into a corresponding link address, or a link-specific problem > of some sort.
		> > A destination node SHOULD send a Destination Unreachable message with > Code 4 in response to a packet for which the transport protocol > (e.g., UDP) has no listener, if that transport protocol has no > alternative means to inform the sender.
	www.mail-archive.com /ipv6@ietf.org/msg01424.html (498 words)

	TCP/IP Tutorial and Technical Overview
		If this message is received from the destination host, it means that the protocol specified in the protocol number field of the original datagram is not active, or that protocol is not active on this host or if the specified port is inactive (see User Datagram Protocol (UDP) for an introduction to the port concept).
		If a router implements the Path MTU Discovery protocol, the format of the Destination unreachable message is changed for code 4 to include the MTU of the link which could not accept the datagram.
		If this message is received from the destination host, it means that the IP fragment reassembly time-to-live timer has expired while the host is waiting for a fragment of the datagram.
	www.cas.mcmaster.ca /~cs4cd3/tcpip/3376c24.htm (2000 words)

	The TCP/IP Guide - ICMPv4 Destination Unreachable Messages
		The receipt of a Destination Unreachable message tells a device that the datagram it sent couldn't be delivered, and the reason for the non-delivery is indicated by the Code field in the ICMP header.
		The destination host specified in the IP address cannot be reached due to inability to provide service specified in the datagram's Type Of Service field.
		Key Concept: ICMPv4 Destination Unreachable messages are used to inform a sending device of a failure to deliver an IP datagram.
	www.tcpipguide.com /free/t_ICMPv4DestinationUnreachableMessages-3.htm (794 words)

	[No title]
		Therefore, the testee node returns, on receiving the probe packet from the tester node, and ICMP Destination Unreachable, Port Unreachable error message to the tester node.
		There is a chance that the default UDP Destination port number used in the probe packet happens to be already being used on the testee node when the probe packet reaches it.
		The Channel Identifier in the xcast header of the probe packet is used for the identification purpose that is to identify the probe packet causing a returned ICMP error message.
	www.ietf.org /proceedings/03mar/I-D/draft-lee-xcast-reachability-00.txt (2904 words)

	Chapter 5 - Part II: Internet Core Protocols \| Page 1 \| May 15, 2000
		For example, Figure 5-29 shows an ICMP Destination Unreachable: Host Unreachable Error message that appears to be very complex on the surface, but actually only consists of a few key pieces of data.
		The ICMP Message Type for this message is 3, which indicates that it is part of the Destination Unreachable family of error messages.
		We can tell from the discussion of Port Unreachable earlier in "Destination Unreachable error messages" that the Destination Unreachable: Port Unreachable error message means that the destination port number specified by the UDP or TCP message was not in a listening state, which generally indicates that there was no server running on that port number.
	www.networkcomputing.com /netdesign/1108icmp1.html?antiRecursionFlag=true (498 words)

	Interesting Traces - Who sent the "destination unreachable, fragmentation needed" message
		Frame 10 is the key its a Destination unreachable fragmentation needed message.
		It doesn't make sense that the NFS_client would send a destination unreachable fragmentation needed message and there is evidence that the sender of this message is NOT the NFS_Client.
		Based on that I strongly suspect that it was the 1700 itself that rebuilt the frame and while it cleared the Don't fragment flag in the rebuilt frame it somehow "remembered" that it was set and generated an error.
	members.cox.net /~ndav1/traces/fragmentation_needed.html (688 words)

	Detecting Worms and Abnormal Activities with NetFlow, Part 2
		The third possible result is that the destination is alive but connection attempts from the worm are not functional, as shown in Figure 3.
		This simply means the destination host is indeed living but the port which the worm is trying to connect is closed.
		There is one important fact about the worm to remember: when it tries to propagate, the destination addresses are typically generated at random, and normally there will be a large number of destination hosts that are not living or functional.
	www.securityfocus.com /infocus/1802 (2755 words)

	[No title]
		ICMP: Destination Unreachable [ALERT] Apr 4@12:17:26.7994891 Original source: 128.46.128.76 Unreachable net: 200.12.64.4 Reported by: 140.222.27.222 Frame Number(s): 79982 MAC: Remote late collisions exceeded the threshold.
		ICMP: Destination Unreachable [ALERT] Apr 4@12:25:47.3321782 Original source: 128.46.128.76 Unreachable net: 200.12.64.4 Reported by: 140.222.27.222 Frame Number(s): 447983 ICMP: Destination Unreachable [ALERT] Apr 4@12:25:47.5408359 Original source: 128.46.154.76 Unreachable net: 198.7.0.2 Reported by: 140.222.27.222 Frame Number(s): 448205 MAC: Remote late collisions exceeded the threshold.
		ICMP: Destination Unreachable [ALERT] Apr 4@12:31:25.3713025 Original source: 128.46.128.76 Unreachable net: 200.12.64.8 Reported by: 140.222.27.222 Frame Number(s): 734071 ICMP: Destination Unreachable [ALERT] Apr 4@12:31:26.2395122 Original source: 128.46.128.76 Unreachable net: 198.7.0.1 Reported by: 140.222.27.222 Frame Number(s): 734497 MAC: Remote late collisions exceeded the threshold.
	www.cse.nd.edu /~curt/ecn/ecneea.txt (287 words)

	Re: ICMP "Destination unreachable" - should it be sent? (Site not responding. Last check: 2007-10-30)
		On Wed, 27 Sep 2000, Stefan Schlott wrote: >..."Destination Unreachable Message > Code 1 - communication with destination administratively prohibited" > Should this message be sent when a packet does not conform to the local > security policy database (spd), or should such packets be silently dis- > carded?
		At most, it might give the receiver a hint that communications difficulties are occurring, but the receiver cannot trust that report without confirming it by other means.
		Prev by thread: Re: ICMP "Destination unreachable" - should it be sent?
	www.sandelman.ottawa.on.ca /ipsec/2000/09/msg00124.html (253 words)

	Internet Control Message Protocol "Destination Unreachable" (Code = 0x0D) Packets
		The code value of the ICMP Destination Unreachable packet is 0x0D.
		The ICMP packet is sent as a response to a DNS name query by using TCP/UDP port 53.
		When a packet is undeliverable, a Destination Unreachable ICMP Type 3 message is generated.
	support.microsoft.com /kb/325122 (651 words)

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