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Old 07-07-2011, 06:17 PM   #1
bulbous23
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need to populate arp dynamically


I've got a bit of a weird situation I think -- running Ubuntu 9.04

I've got a dev machine where we've set up multihoming via this in the interfaces file:

auto eth0:1
iface eth0:1 inet static
address 10.0.2.22
netmask 255.255.255.0
network 10.0.2.0
broadcast 10.0.2.255

so that we can have multiple https hosts.

When we first set this up, other machines on our corporate network could not see ping the 10.0.2.22 address, even though they could ping the main address for this machine. (they get this error: 92 bytes from 10.5.0.1: Destination Host Unreachable)


after executing this command:
route add -host 8.8.8.8 dev eth0:1
and then
ping 8.8.8.8

other machines on the network could then ping the 10.0.2.22 address just fine.

I concluded that there was an arp problem, and so I set up a periodic ping in case the arp cache got flushed (I did this after it got flushed one time, and we lost connectivity again).

This all seems like a huge hack to me, with the right solution being to modify the 10.5.0.1 arp settings or something (although it seems like it is probably generally set up dynamically).

recently the network architecture at my work changed (I don't have any control over that, I just need my server to work), and now my ping solution isn't working -- any ideas?

Thanks much
Cheers
Kem
 
Old 07-10-2011, 11:53 PM   #2
kbp
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It may be worth trying a packet sniffer (tcpdump, wireshark) to see what's really going on.
 
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Old 07-11-2011, 04:51 PM   #3
jefro
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Nic's chatter all the time. They send out arp requests and hold them for a time. You don't populate it dynamically. It is done automatically. You populate static by command if you want it there for longer times.

If you have a switch it may hold the arp page for a long time and you may be able to hold it there forever even depending on model.
 
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Old 07-11-2011, 04:57 PM   #4
bulbous23
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Registered: Oct 2005
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Thanks much both of you -- I'm not very familiar with ARP, but suspected it was supposed to work automatically. Am investigating what is going on further (thanks for the tcpdump / wireshark suggestion, I've used them before for other issues, but for some reason didn't think to use it here, so
 
  


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