Re: Linux network behavior wierdness
Neil Joseph Schelly <[EMAIL PROTECTED]> writes: >> Fascinating, so how does this work? >> >> $ ssh farm-519 ping -b 10.95.255.255 -c 1 >> 64 bytes from 10.95.34.112: icmp_seq=1 ttl=64 time=0.074 ms >> 1 packets transmitted, 1 received, 0% packet loss, time 0ms >> >> $ ssh farm-519 cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts >> 1 > > ping -b "farm-519's broadcast" ...ought to have no response from > farm-519. It won't respond to them, but it can still send broadcast > pings. Right, but by that rational, when I'm on farm-519 and I 'ping -b 10.95.255.255', and assuming all hosts on that /16 subnet are configure similarly (such that /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts == 1) shouldn't I see no response at all ? I can almost guarantee that all hosts have this set, as it's the default for the kernel we're running. Thanks. -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
Paul Lussier writes: > Paul Lussier <[EMAIL PROTECTED]> writes: > > >> Watch out for /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts. The > >> default was changed between 2.6.13 and 2.6.14 to ignore by default. > > > > Ooh, I didn't know that, thanks! > > Fascinating, so how does this work? > > $ ssh farm-519 ping -b 10.95.255.255 -c 1 > 64 bytes from 10.95.34.112: icmp_seq=1 ttl=64 time=0.074 ms > 1 packets transmitted, 1 received, 0% packet loss, time 0ms > > $ ssh farm-519 cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts > 1 Ping can still send, just farm-519's kernel won't reply. I'd assume 10.95.34.112 is some other host on the network that does reply right? -- Dave ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
Darrell Michaud writes: > There also might be a tiny possibility that the infrastructure switches > are filtering or otherwise interfering with the broadcast ping. > > It might we worth testing with with a single dumb switch, or even a > crossover cable. I second this recommendation. If there is any network gear in this setup that is filtering out directed broadcasts, this might explain some of the strangeness. Regards, --kevin -- GnuPG ID: B280F24EMeet me by the knuckles alumni.unh.edu!kdcof the skinny-bone tree. http://kdc-blog.blogspot.com/ -- Tom Waits ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
On Friday 05 September 2008 14:26, Paul Lussier wrote: > Paul Lussier <[EMAIL PROTECTED]> writes: > >> Watch out for /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts. The > >> default was changed between 2.6.13 and 2.6.14 to ignore by default. > > > > Ooh, I didn't know that, thanks! > > Fascinating, so how does this work? > > $ ssh farm-519 ping -b 10.95.255.255 -c 1 > 64 bytes from 10.95.34.112: icmp_seq=1 ttl=64 time=0.074 ms > 1 packets transmitted, 1 received, 0% packet loss, time 0ms > > $ ssh farm-519 cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts > 1 ping -b "farm-519's broadcast" ...ought to have no response from farm-519. It won't respond to them, but it can still send broadcast pings. -N ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
Paul Lussier <[EMAIL PROTECTED]> writes: >> Watch out for /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts. The >> default was changed between 2.6.13 and 2.6.14 to ignore by default. > > Ooh, I didn't know that, thanks! Fascinating, so how does this work? $ ssh farm-519 ping -b 10.95.255.255 -c 1 64 bytes from 10.95.34.112: icmp_seq=1 ttl=64 time=0.074 ms 1 packets transmitted, 1 received, 0% packet loss, time 0ms $ ssh farm-519 cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts 1 -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
"Ben Scott" <[EMAIL PROTECTED]> writes: > On Fri, Sep 5, 2008 at 10:04 AM, Paul Lussier <[EMAIL PROTECTED]> wrote: >> Any insights would be most appreciated. > > In addition to the other (probably better) things people have > suggested, are any of these hosts running an iptables firewall with > connection tracking? Definitely not. > State table overflow can lead to weird behaviors like what you > describe. I've found that just running Linux "can lead to weird behaviors like what you describe." :-/ -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
Dave Johnson <[EMAIL PROTECTED]> writes: > 10.95.0.0 is an unusual broadcast address, how did you end up with > that? It's a /16 network. 10.95.255.255 exhibits identical behavior fwiw. > Watch out for /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts. The > default was changed between 2.6.13 and 2.6.14 to ignore by default. Ooh, I didn't know that, thanks! -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
On Fri, Sep 5, 2008 at 10:04 AM, Paul Lussier <[EMAIL PROTECTED]> wrote: > Any insights would be most appreciated. In addition to the other (probably better) things people have suggested, are any of these hosts running an iptables firewall with connection tracking? State table overflow can lead to weird behaviors like what you describe. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
RE: Linux network behavior wierdness
There also might be a tiny possibility that the infrastructure switches are filtering or otherwise interfering with the broadcast ping. It might we worth testing with with a single dumb switch, or even a crossover cable. ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
RE: Linux network behavior wierdness
The all-zeroes broadcast address was de rigeur for SunOS 4.x systems, and systems of later vintage than that typically used all-ones. As I recall, many modern systems won't recognize all-zero as a broadcast address unless they're instructed to. This may explain the different outcomes on different systems. I'd also suggest you double-check your netmasks - a packet to 192.168.128.255 won't be responded to unless the receiving system's netmask is such that the left half of the origin address matches its idea of the network, and the right half is all-1. -Michael Pelletier. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Lussier Sent: Friday, September 05, 2008 10:04 AM To: gnhlug-discuss@mail.gnhlug.org Subject: Linux network behavior wierdness Hi all, I have a wierd problem where some hosts respond to a broadcast ping packet and others don't. I have some hosts which, when I do a ping -b 10.95.0.0 everything answers. On other hosts, doing exactly the same thing, I get no response. A reboot resets a "broken" host, but over time it will re-develop the problem. And I can't seem to figure out how to make the problem occur... I can't figure out if it's something we're doing which is causing this change, or if it's a kernel thing where some threshold is reached and it just stops. Fwiw, we're running Debian/Etch with a 2.6.18 kernel. Most NICs are Intel e1000, though some are broadcom. In general, I've seen it happen across our lab on different hardware platforms with different motherboards and nics. Any insights would be most appreciated. -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/ ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Linux network behavior wierdness
Paul Lussier writes: > > Hi all, > > I have a wierd problem where some hosts respond to a broadcast ping > packet and others don't. > > I have some hosts which, when I do a ping -b 10.95.0.0 everything answers. > On other hosts, doing exactly the same thing, I get no response. > > A reboot resets a "broken" host, but over time it will re-develop the problem. > And I can't seem to figure out how to make the problem occur... > > I can't figure out if it's something we're doing which is causing this > change, or if it's a kernel thing where some threshold is reached and > it just stops. > > Fwiw, we're running Debian/Etch with a 2.6.18 kernel. Most NICs are > Intel e1000, though some are broadcom. In general, I've seen it > happen across our lab on different hardware platforms with different > motherboards and nics. > > Any insights would be most appreciated. 10.95.0.0 is an unusual broadcast address, how did you end up with that? Watch out for /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts. The default was changed between 2.6.13 and 2.6.14 to ignore by default. -- Dave ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Linux network behavior wierdness
Hi all, I have a wierd problem where some hosts respond to a broadcast ping packet and others don't. I have some hosts which, when I do a ping -b 10.95.0.0 everything answers. On other hosts, doing exactly the same thing, I get no response. A reboot resets a "broken" host, but over time it will re-develop the problem. And I can't seem to figure out how to make the problem occur... I can't figure out if it's something we're doing which is causing this change, or if it's a kernel thing where some threshold is reached and it just stops. Fwiw, we're running Debian/Etch with a 2.6.18 kernel. Most NICs are Intel e1000, though some are broadcom. In general, I've seen it happen across our lab on different hardware platforms with different motherboards and nics. Any insights would be most appreciated. -- Seeya, Paul ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
