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/
