68.15.53.174 and 68.15.53.176 are the connections to the Internet for two
schools. The subnet mask is 255.255.255.128. Both connections are via cable
modems, most likely on the same cable segment. 10.4.56.1 must be the Cox
Communications router on the head end. When I traceroute from either side to
the other, it shows up as 1st in the traceroute output. An interesting thing
is that both traceroutes do not complete successfully to the other end.
However, a traceroute -I completes in two hops.
[root@allsrv01 root]# traceroute 68.15.53.176
traceroute to 68.15.53.176 (68.15.53.176), 30 hops max, 38 byte packets
1 10.4.56.1 (10.4.56.1) 8.714 ms 10.247 ms 9.723 ms
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * *
[root@allsrv01 root]#
[root@squidhs root]# traceroute -I 68.15.53.174
traceroute to 68.15.53.174 (68.15.53.174), 30 hops max, 38 byte packets
1 10.4.56.1 (10.4.56.1) 8.854 ms 7.689 ms 8.126 ms
2 wsip68-15-53-174.ri.ri.cox.net (68.15.53.174) 21.487 ms 23.157 ms 15.164
ms
[root@squidhs root]#
Quoting Ramin Alidousti <[EMAIL PROTECTED]>:
> What is your network setup/topology? In short, this is an ICMP
> redirect sent by 10.4.56.1 to 68.15.53.174 saying that if you
> want to send packets to 68.15.53.176 send it to 68.15.53.176
> and not me (10.4.56.1). This does not make sense, right? But
> in order to fully explain the why/how/who/what you have to
> tell us the topology.
>
> Ramin
>
> On Mon, Apr 29, 2002 at 03:47:50PM -0400, Mark Orenstein wrote:
>
> > Can I have some help with an explanation of the following message in
> the log.
> > I'm just getting started with GRE. It seems to be working. The log
> message
> > was caused by a rule in the iptable INPUT chain.
> >
> > "DROP icmp" is my own log hdr.
> > eth2 is the external device with IP address 68.15.53.174 which is the
> local end
> > of the GRE tunnel. 68.15.53.176 is the remote end of the tunnel.
> > Where does 10.4.56.1 come from? What does the stuff in [ ] mean?
> >
> > Below is the message.
> >
> > Apr 29 13:18:43 allsrv01 kernel: DROP icmp IN=eth2 OUT=
> > MAC=00:c0:f0:45:76:18:00:05:5f:e9:9c:54:08:00 SRC=10.4.56.1
> DST=68.15.53.174
> > LEN=56 TOS=0x00 PREC=0x00 TTL=255 ID=53630 PROTO=ICMP TYPE=5 CODE=1
> > GATEWAY=68.15.53.176 [SRC=68.15.53.174 DST=68.15.53.176 LEN=64
> TOS=0x00
> > PREC=0x00 TTL=126 ID=0 DF PROTO=47 ]
> >
> > Mark Orenstein
>
