Re: ICMP Router Discovery
Re: ICMP Router Discovery
- Subject: Re: ICMP Router Discovery
- From: Chase <email@hidden>
- Date: Tue, 28 Jun 2005 18:02:26 -0500
Pinging 224.0.0.2 should get replies from everything that thinks
its a router and cares for answering.
I'm not sure if it helps but it's something...
Of course you still wouldn't get the routes they're routing.
hmmm... just tried "ping 224.0.0.2", but it just hangs there,
getting no reponses from anything.
i like this idea though (in terms of portability). can you help me
figure out what i'm doing wrong?
okay, i just played around a little with this.
i tried pinging 224.0.0.0 thru 224.0.0.100 (and a few toward the top
of the range as well), and i could get responses from one of the
routers, but not the other.
the responses from the one router were provoked by pinging 224.0.0.9
but, again, the other router didn't respond to any of the 224.0.0.xxx
pings.
BUT... i tried pinging 192.168.0.255 and 192.168.1.255 and i got
something very interesting and useful:
PING 192.168.0.255 (192.168.0.255): 56 data bytes
64 bytes from 192.168.0.102: icmp_seq=0 ttl=64 time=0.180 ms
64 bytes from 192.168.0.250: icmp_seq=0 ttl=64 time=1.905 ms (DUP!)
64 bytes from 192.168.0.102: icmp_seq=1 ttl=64 time=0.177 ms
64 bytes from 192.168.0.250: icmp_seq=1 ttl=64 time=1.512 ms (DUP!)
64 bytes from 192.168.0.102: icmp_seq=2 ttl=64 time=0.168 ms
64 bytes from 192.168.0.250: icmp_seq=2 ttl=64 time=1.723 ms (DUP!)
64 bytes from 192.168.0.102: icmp_seq=3 ttl=64 time=0.176 ms
64 bytes from 192.168.0.250: icmp_seq=3 ttl=64 time=1.506 ms (DUP!)
64 bytes from 192.168.0.102: icmp_seq=4 ttl=64 time=0.174 ms
64 bytes from 192.168.0.250: icmp_seq=4 ttl=64 time=1.648 ms (DUP!)
PING 192.168.1.255 (192.168.1.255): 56 data bytes
64 bytes from 192.168.1.104: icmp_seq=0 ttl=64 time=0.295 ms
64 bytes from 192.168.1.250: icmp_seq=0 ttl=150 time=4.961 ms (DUP!)
64 bytes from 192.168.1.250: icmp_seq=0 ttl=150 time=32.736 ms (DUP!)
64 bytes from 192.168.1.104: icmp_seq=1 ttl=64 time=0.265 ms
64 bytes from 192.168.1.250: icmp_seq=1 ttl=150 time=5.069 ms (DUP!)
64 bytes from 192.168.1.104: icmp_seq=2 ttl=64 time=0.281 ms
64 bytes from 192.168.1.250: icmp_seq=2 ttl=150 time=4.240 ms (DUP!)
64 bytes from 192.168.1.104: icmp_seq=3 ttl=64 time=0.265 ms
64 bytes from 192.168.1.250: icmp_seq=3 ttl=150 time=4.276 ms (DUP!)
for each icmp_seq, there is a single pair:
my ip (192.168._.10_)
router ip (192.168._.250)
(not always in that order).
there are other hosts on both LANs and yet none of those hosts are
responding.
this is great. i'm not complaining at all. quite the contrary.
but, could someone explain why no other hosts on the subnet(s) are
responding? i'm obviously missing something key to how messages are
broadcast locally.
if this turns out to be consistently predictable (pinging the
broadcast address of the subnet yields **ONLY** results from oneself
and the router on that subnet), then i can just look thru the ping
source, pull out the relevant parts, and simply filter out responses
from the local address. that should always give me the router
address, right?
thanks.
- chase
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