Any chance you have more than one LPAR, and they have the same MACPREFIX? We had some strange issues here too, when two machines can contact every single other, but cannot contact themselves, and on certain times of the day they simply dropped out of the network, just to be available minutes later without any error message. We joked about it, saying it was a burnt MAC. We found out that the LPARs had the same MACPREFIX, and those two machines ended up having the same MAC address. The switch got confused, and sent packets to the wrong port.
Mauro http://mauro.limeiratem.com - registered Linux User: 294521 Scripture is both history, and a love letter from God. 2016-02-10 12:53 GMT-02:00 Agblad Tore <[email protected]>: > Thank you, good tips but had no effect. > > I set that to 1 (it was 0) and checked all announces: > > root@zlintcp2:/home/tore# sysctl -a|grep announce > net.ipv4.conf.all.arp_announce = 1 > net.ipv4.conf.default.arp_announce = 0 > net.ipv4.conf.lo.arp_announce = 0 > net.ipv4.conf.eth0.arp_announce = 0 > net.ipv4.conf.eth1.arp_announce = 0 > net.ipv4.conf.eth2.arp_announce = 0 > > This however had no effect, but since there also was a specification of 0 > for eth2 (my backupLan) I wondered which one takes precedence here? > So I fixed that one as well: > > root@zlintcp2:/home/tore# sysctl -w net.ipv4.conf.eth2.arp_announce=1 > net.ipv4.conf.eth2.arp_announce = 1 > root@zlintcp2:/home/tore# sysctl -a|grep announce > net.ipv4.conf.all.arp_announce = 1 > net.ipv4.conf.default.arp_announce = 0 > net.ipv4.conf.lo.arp_announce = 0 > net.ipv4.conf.eth0.arp_announce = 0 > net.ipv4.conf.eth1.arp_announce = 0 > net.ipv4.conf.eth2.arp_announce = 1 > > Still no effect. > I will take some more tcpdump on all interfaces as you suggested. > > > BR /Tore > > ________________________________________________ > Tore Agblad > zOpen, IT Services > > Volvo Group Headquarters > Corporate Process & IT > SE-405 08, Gothenburg Sweden > E-mail: [email protected] > http://www.volvo.com/volvoit/global/en-gb/ > > -----Original Message----- > From: Linux on 390 Port [mailto:[email protected]] On Behalf Of > Robert J Brenneman > Sent: den 9 februari 2016 5:14 > To: [email protected] > Subject: Re: TSM backup LAN connection problem > > Multi homed linux seems to consider any MAC address as good as any other > when responding to an ARP. The default seems to assume you have every > ethernet port plugged to the same logical network. If you run tcpdump on > all interfaces for both machines, I bet you see the target of the telnet > request sometimes responding to the ARP out the wrong interface with the > wrong MAC address. > > Try this - on both your Linux x86 and Linux s390x systems, set this > variable in /etc/sysctl.conf > net.ipv4.conf.all.arp_announce = 1 > > and make it effective with 'sysctl -p /etc/sysctl.conf' > > see also: > > http://kb.linuxvirtualserver.org/wiki/Using_arp_announce/arp_ignore_to_disable_ARP > > On Tue, Feb 9, 2016 at 9:04 AM, Grzegorz Powiedziuk <[email protected] > > > wrote: > > > Is it only telnet acting like this? What about ping, netcat (nc)? Does > it > > respond promptly? > > usually delays with logins (ssh but I think telnet does the same thing) I > > have caused by messed up DNS and reverse lookup entries. But here it is > > different because it works fine after first try. > > > > I think the default timeout for arp entries in linux is 60 sec > > (cat /proc/sys/net/ipv4/neigh/default/gc_stale_time) > > you can run "arp -n" to see if it is still there > > > > Did you double check ip configuration and make sure that network, subnet > > and broadcast addresses are correct? > > > > Regards > > Gregory > > > > 2016-02-09 4:04 GMT-05:00 Agblad Tore <[email protected]>: > > > > > Hi, just a long shot perhaps, checking if anyone else have had this > > > problem and solved it: > > > > > > Two Linux servers running TSM(backup server) software, one x86 and on > > > s390x (RHEL 6.7) > > > > > > Both have an extra NIC connected to a separate backup LAN, separate OSA > > > adapters + separate cables all the way. > > > > > > Connection test method: telnet ipaddress 1500 > > > > > > Connect from s390x via that vlan and port 1500 into the x86 server > works, > > > but takes 5-10 seconds first time. And again 5-10 seconds if no traffic > > for > > > about 5 minutes. > > > > > > Connect from x86 same method does not work, unless a connection from > > s390x > > > was made the last 5 minutes. > > > > > > It seems the arp cache in the x86 server is updated and that server > finds > > > it way after that, but timeout is 5 minutes, so after that it does not > > find > > > it's way. > > > > > > I took a tcpdump on that backup lan interface, got some help > > understanding > > > it using wireshark, and obviously the x86 connection tries does > initiate > > an > > > arp query to the s390x server that also replies with its mac address, > as > > it > > > should. Still this does not help. > > > Route tables also looks as expected, should not cause a problem. > > > > > > Anyone having seen this problem ? > > > If you also have the solution you will make my day :-) > > > > > > BR /Tore > > > > > > ________________________________________________ > > > Tore Agblad > > > zOpen, IT Services > > > > > > Volvo Group Headquarters > > > Corporate Process & IT > > > SE-405 08, Gothenburg Sweden > > > E-mail: [email protected] > > > http://www.volvo.com/volvoit/global/en-gb/ > > > > > > ---------------------------------------------------------------------- > > > For LINUX-390 subscribe / signoff / archive access instructions, > > > send email to [email protected] with the message: INFO LINUX-390 > or > > > visit > > > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > > ---------------------------------------------------------------------- > > > For more information on Linux on System z, visit > > > http://wiki.linuxvm.org/ > > > > > > > ---------------------------------------------------------------------- > > For LINUX-390 subscribe / signoff / archive access instructions, > > send email to [email protected] with the message: INFO LINUX-390 or > > visit > > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > ---------------------------------------------------------------------- > > For more information on Linux on System z, visit > > http://wiki.linuxvm.org/ > > > > > > -- > Jay Brenneman > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or > visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- > For more information on Linux on System z, visit > http://wiki.linuxvm.org/ > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
