traceroute works by using incrementally-larger ip ttl's on packets.
the "ip ttl" check is typically performed on an 'ingress' interface on a
router -- with the icmp "time exceeded" response originating from the ip
address 'facing' your route.
icmp echo-request with "record route" set updates the icmp packet on
'egress'.
the reasons are mostly historic -- and associated with "source route" (such
that one could 'reverse' the path and then you have the list of next-hops
for source-routing a packet back).
cheers,
lincoln.
At 09:35 03/03/00 +1100, Howard Lowndes wrote:
>I have just discovered an interesting disparity in the interfaces that are
>reported by traceroute and ping:
>
>[lannet@hero lannet]$ /usr/sbin/traceroute auf.asn.au
>traceroute to auf.asn.au (203.37.104.194), 30 hops max, 40 byte packets
> 1 janus (203.41.237.73) 1.033 ms 0.837 ms 0.804 ms
> 2 gw.alb2.Albury.telstra.net (139.130.60.65) 142.913 ms 139.184 ms
>139.711 ms
> 3 Ethernet0.alb1.Albury.telstra.net (139.130.240.33) 129.828 ms
>144.659 ms 139.781 ms
..
>[lannet@hero lannet]$ ping -Rc1 auf.asn.au
>PING auf.asn.au (203.37.104.194): 56 data bytes
>64 bytes from 203.37.104.194: icmp_seq=0 ttl=247 time=466.5 ms
>RR: hero.lannet.com.au (203.41.237.74)
> janus.lannet.com.au (139.130.60.92)
> Ethernet0.alb2.Albury.telstra.net (139.130.240.34)
> Serial0.alb1.Albury.telstra.net (203.50.76.30)
> Fddi0-0.lon-core2.Melbourne.telstra.net (139.130.239.227)
> Pos2-0.lon-core3.Melbourne.telstra.net (203.50.6.81)
> Ethernet1-0.civ-core1.Canberra.telstra.net (139.130.235.65)
> scout.auf.asn.au (203.37.104.193)
> stratos.auf.asn.au (203.37.104.194)
--
SLUG - Sydney Linux Users Group Mailing List - http://www.slug.org.au
To unsubscribe send email to [EMAIL PROTECTED] with
unsubscribe in the text
