[ale] Re: ICMP Source route failed

[Omar Loggiodice]

Mir S Islam Writes :
:
:Hi, I got this messages in my /var/adm/messages. Any idea what it means ? 
:Thanks. I have seen similar messages earlier, but from different IP 
:addresses.
:
:Jul 25 18:12:39 venus kernel: ICMP: 134.134.131.6: Source Route Failed.

Hi,

   Before answering the question, I'll give you some background information
   that is needed to understand what the above message means.

   As you probably know, TCP/IP is a suite of protocols as opposed to two
   protocols (TCP and IP). One of the protocols that is included in the
   TCP/IP suite is called ICMP (Internet Control Message Protocol). The TCP
   protocol is a "reliable" protocol, meaning that it can guarantee delivery
   of packets (or it will return an error). Many protocols at the lower
   layers --such as UDP or IP-- are not reliable; in other words, there is
   no guarantee that the packet will reach the destination, that the
   datagram will not be lost or that datagrams will arrive in a specific
   order.

   It is, therefore, important to have a mechanism for hosts and gateways to
   deliver control messages such as "Destination Unreachable" or "Time
   Exceeded". The protocol used to transfer this kind of messages is called
   ICMP.
   
   Now you know what ICMP is. 
   
   IP datagrams also contain "options" that dictate the behaviour of the
   IP layer in gateways and hosts. This options are used when source hosts
   want some specific datagram behaviour. They are not mandatory (that is
   why they are options). There are options for special routing, for recording
   the route a datagram takes, etc. 

   One of this options is called "Source routing"(*). This option allows a
   source host to specify the route that a datagram should take. The above
   message --a control ICMP message sent from a gateway-- means that the
   gateway received an IP datagram with a Source route option an that it was
   unable to honor the request for source routing.
   
   Hope it helps. 


   (*) Actually there are two types of source routing options (strict and
   loose) but it is best to keep it simple in the explanation. 


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