[j-nsp] Need help on ping output
Thu, 14 Nov 2002 17:59:46 -0000
> Hi guy,
> Thanks for replying.
> > The address 10.254.1.2 is the source of the packets being
> sent back to
> > "router" with ICMP Destination Host Unreachable messages in
> them. That
> > means that your packets reached a router which had no route to the
> > destination host. I suggest that you identify the location of that
> Is it possible that 10.254.1.2 is denying ICMP and thus
> return the ICMP Dest
> Host Unreachable? But it somehow allows other traffic
> (non-ICMP) through?
Unlikely. Is 10.254.1.2 the same host as the far end of the link
> Could an ACL might cause this kind of ping reply?
No, that would generate a different error.
> In any case, what does each entry mean? (e.g Vr, HL .etc):
> 36 bytes from 10.254.1.2: Destination Host Unreachable
> Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
> 4 5 00 0054 e4db 0 0000 fe 01 2b8d 18.104.22.168
Vr - Version (IPv4)
HL - Header Length?
TOS - Type of Service byte
Len - Length in bytes
ID - Fragment ID?
Flg - Flag (fragmentation?)
off - offset (from the beginning of the first fragment?)
TTL - Time to Live (255 in this case)
Pro - protocol? 1=ICMP
cks - checksum
Src - source
Dst - destination
> > You need to check that the interface is actually up and
> you're not using
> > some alternative path to reach destinations "beyond" your ATM link.
> > I'd also suggest that you check your routing table and
> forwarding table to
> > see what the next hop for 192.168.21.133 is. If you don't
> see it using
> > command "show route <blah>" then try "show route <blah>
> hidden extensive".
> > That might show you that the route is actually being
> filtered (perhaps
> > because 192.168.0.0/16 has been added to your martians?).
> If this is the
> > case, the packet may be using a default route to reach
> 10.254.1.2 but, if
> > that router is injecting the default, there will be no
> forwarding path
> > there.
> There is no other path to reach 192.168.21.133. "show route
> <blah>" shows
> that the IP is learned via a connected subnet.
> router> show route 192.168.21.133
> + = Active Route, - = Last Active, * = Both
> 192.168.21.132/30 *[Direct/0] 2d 17:54:22
> > via at-0/0/0.6
> I've checked that the route has not been added to the martian list.
This e-mail is private and may be confidential and is for the intended
recipient only. If misdirected, please notify us by telephone and confirm
that it has been deleted from your system and any copies destroyed. If you
are not the intended recipient you are strictly prohibited from using,
printing, copying, distributing or disseminating this e-mail or any
information contained in it. We use reasonable endeavors to virus scan all
e-mails leaving the Company but no warranty is given that this e-mail and
any attachments are virus free. You should undertake your own virus
checking. The right to monitor e-mail communications through our network is
reserved by us.