Date: Wed, 21 Jun 2000 22:19:27 -0700 From: "Crist J. Clark" <cristjc@earthlink.net> To: The Clark Family <res03db2@gte.net> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Confused by Loopback Message-ID: <20000621221927.B43715@pool0586.cvx20-bradley.dialup.e> In-Reply-To: <Pine.BSF.4.21.0006212107220.46613-100000@orthanc.dsl.gtei.net>; from res03db2@gte.net on Wed, Jun 21, 2000 at 09:09:25PM -0700 References: <20000621205221.A43715@pool0586.cvx20-bradley.dialup.e> <Pine.BSF.4.21.0006212107220.46613-100000@orthanc.dsl.gtei.net>
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On Wed, Jun 21, 2000 at 09:09:25PM -0700, The Clark Family wrote: > > Do you have an lo0 device in rc.conf? Sure do. That's the ifconfig(8) output below. > There was a bug (for a while) that caused lo0 to not be setup? Yeah, the classic symptom was people not being able to talk to their portmappers. > People sometimes delete lo0 from their rc.conf. $ grep lo0 /etc/rc.conf network_interfaces="lo0" > I'd expect a netstat -in to show up the loopback pseudo-device. Interesting. Yep, it is in there, $ netstat -in Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll lp0* 1500 <Link#1> 0 0 0 0 0 lo0 16384 <Link#2> 126 0 126 0 0 lo0 16384 127 127.0.0.1 126 0 126 0 0 tun0 1500 <Link#3> 11500 0 11421 0 0 tun0 1500 209.179.192.1 209.179.192.189 11500 0 11421 0 0 And that is a weird entry for tun0 there. But still not in the routing table, $ netstat -rn Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire default 207.217.148.34 UGSc 2 27 tun0 127.0.0.1 127.0.0.1 UH 0 52 lo0 207.217.148.34 209.179.192.189 UH 3 0 tun0 And the packets still fly down tun0, $ traceroute 127.2 traceroute to 127.2 (127.0.0.2), 30 hops max, 40 byte packets 1 * * * 2 207.217.148.33 (207.217.148.33) 180.139 ms 138.387 ms 139.520 ms 3 vlan296-cr04-pas.neteng.itd.earthlink.net (207.217.2.101) 139.409 ms 138.369 ms 129.653 ms 4 * *^C And I can watch 'em go with a tcpdump(8) too. Oh, and I'll post my favorite, $ ping 127.255.255.255 PING 127.255.255.255 (127.255.255.255): 56 data bytes 64 bytes from 207.217.2.37: icmp_seq=0 ttl=253 time=781.779 ms 64 bytes from 207.217.2.69: icmp_seq=1 ttl=253 time=160.467 ms 64 bytes from 207.217.2.101: icmp_seq=2 ttl=253 time=160.400 ms 64 bytes from 207.217.2.101: icmp_seq=3 ttl=253 time=161.568 ms 64 bytes from 207.217.2.69: icmp_seq=4 ttl=253 time=159.994 ms 64 bytes from 207.217.2.69: icmp_seq=5 ttl=253 time=150.441 ms 64 bytes from 207.217.2.15: icmp_seq=6 ttl=253 time=153.001 ms ^C --- 127.255.255.255 ping statistics --- 8 packets transmitted, 7 packets received, 12% packet loss round-trip min/avg/max/stddev = 150.441/246.807/781.779/218.437 ms I wish nmap(1) worked well over a PPP link; I'd love to know what OSes are replying to those. > [RC] > > On Wed, 21 Jun 2000, Crist J. Clark wrote: > > > I think I must be missing something... But I am not sure what. > > > > My loopback is configured so, > > > > $ ifconfig lo0 > > lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384 > > inet 127.0.0.1 netmask 0xff000000 > > > > But if I look at the routing table, > > > > $ netstat -rn > > Routing tables > > > > Internet: > > Destination Gateway Flags Refs Use Netif Expire > > default 207.217.148.27 UGSc 11 22 tun0 > > 127.0.0.1 127.0.0.1 UH 0 0 lo0 > > 207.217.148.27 209.179.254.29 UH 12 0 tun0 > > > > Notice there is no LAN entry for the 127-net like the ifconfig(8) mask > > says. So if I were to do something silly like, > > > > $ ping 127.0.0.2 > > > > It goes out over the tun0 interface. I noticed this because for some > > perverse reason I tried, > > > > $ ping 127.255.255.255 > > > > And started getting replies from other hosts! I tried a traceroute(8) > > and watched 127.0.0.2 packets make their happy way out towards the > > I'net. > > > > Tell me I'm missing something silly here. > > -- > > Crist J. Clark cjclark@alum.mit.edu > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > with "unsubscribe freebsd-questions" in the body of the message > > > -- Crist J. Clark cjclark@alum.mit.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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