From: Kyaw Khine (kkhine@register.com)
Date: Tue Nov 19 2002 - 20:52:01 GMT-3
Destination unreachable is ICMP type 3.
Type-3 have serveral codes. Among them ..
0 Net Unreachable
1 Host Unreachable
2 Protocol Unreachable
3 Port Unreachable
etc.
In case of traceroute, it's type-3 code-3.
- Kyaw Khine
-----Original Message-----
From: Chuck Church [mailto:cchurch@optonline.net]
Sent: Tuesday, November 19, 2002 6:23 PM
To: Kyaw Khine
Cc: ccielab@groupstudy.com
Subject: Re: Lost packet in traceroute
That's weird. I had played around with it a little on my router here at
home. I set the timeout to 30000 ms (30 seconds) and tracerouted to that
router. I got three replies out of three, where I should have only received
1. The doc mentions destination unreachable. But does that refer to
'host-unreachable' or 'port-unreachable'?
Chuck Church
CCIE #8776, MCNE, MCSE
----- Original Message -----
From: "Kyaw Khine" <kkhine@register.com>
To: "'Chuck Church'" <cchurch@optonline.net>
Cc: <ccielab@groupstudy.com>
Sent: Tuesday, November 19, 2002 5:04 PM
Subject: RE: Lost packet in traceroute
> Chuck,
>
> Yes. It actually fixed my problems. So, modifying rate of 'host
> unreachables' helps. (default is 1 reply every 500 milliseconds and I
> make it lower, which might not be a good idea for ping floods.)
>
> It is true that traceroute relies on TTL expired ICMPs for
> intermediate routers along the path. But, at final destination, it
> ends up with ICMP Destination Unreachable (type 3) Port Unreachable
> (code 3).
>
> Pls refer to
> (ip icmp rate-limit unreachable command reference)
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr
> as_r/1rfip1.htm#1068044
>
> (how traceroute works)
>
http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration
> _guide_chapter09186a008007f63a.html#xtocid6
>
> (icmp type codes)
> http://www.spirit.com/Resources/icmp.html
>
>
> - Kyaw Khine
>
>
> For those who don't want bother visiting CCO,
>
> "
> To identify the next hop, traceroute sends a UDP packet with a TTL
> value
of
> 2. The first router decrements the TTL field by 1 and sends the
> datagram
to
> the next router. The second router sees a TTL value of 1, discards the
> datagram, and returns the time-exceeded message to the source. This
process
> continues until the TTL is incremented to a value large enough for the
> datagram to reach the destination host (or until the maximum TTL is
> reached).
>
> To determine when a datagram reaches its destination, traceroute sets
> the UDP destination interface in the datagram to a very large value
> which the destination host is unlikely to be using. When a host
> receives a datagram with an unrecognized interface number, it sends an
> ICMP port unreachable error to the source. This message indicates to
> the traceroute facility
that
> it has reached the destination.
> "
>
>
>
> -----Original Message-----
> From: Chuck Church [mailto:cchurch@optonline.net]
> Sent: Tuesday, November 19, 2002 4:43 PM
> To: Kyaw Khine; ccielab@groupstudy.com
> Subject: Re: Lost packet in traceroute
>
>
> Kyaw,
>
> Did that actually fix your problem? According to the docs, it
modifies
> the rate that 'host unreachables' are sent. Traceroute relies on TTL
> expired ICMPs
>
> Chuck Church
> CCIE #8776, MCNE, MCSE
>
>
> ----- Original Message -----
> From: "Kyaw Khine" <kkhine@register.com>
> To: <ccielab@groupstudy.com>
> Sent: Tuesday, November 19, 2002 2:19 PM
> Subject: RE: Lost packet in traceroute
>
>
> > I found out the solution.
> >
> > Ip icmp rate-limit unreachable <time>
> >
> >
> > -----Original Message-----
> > From: Kyaw Khine
> > Sent: Tuesday, November 19, 2002 1:55 PM
> > To: 'ccielab@groupstudy.com'
> > Subject: Lost packet in traceroute
> >
> >
> > Hi Group,
> >
> > I'm seeing a packet drop when I traceroute to a neighbor router.
> > It's
> always
> > like this that the middle packet is dropped.
> >
> > Tracing the route to
> > 1 s4-0.core1.nyat.register.com (209.67.51.1) 4 msec * 4 msec
> >
> > Any thoughts what is going on?
> >
> >
> > Thanks ..
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