06-12-2013 05:23 AM - edited 03-07-2019 01:51 PM
Hello
I have 2 servers, one active, the other standby, both will be using the same IP. If the active fails then a re-patch for the standby to make this the active.
I undersatnd that i will need to clear the arp & maybe mac address table on the 6500 for the new active server to work, as the failed server will have its mac address on the 6500,.
is there a way around this so i dont have to clear the arp cache & clear the mac table?
EXAMPLE
SERVER IP MAC
ACTIVE 192.168.10.50 0050:1234:5678:9101
STANDBY 192.168.10.50 0050:1234:5678:3896
Will a static arp entry work?
06-12-2013 05:31 AM
I would have thought that servers would G-ARP out its mac in the event of a switch over? This would mean that ARP tables are updated automatically? Meaning you wouldn't have to do anything. Is this not the case?
http://wiki.wireshark.org/Gratuitous_ARP
When you mean re-patch, is that physically re-patching cables?
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06-12-2013 06:01 AM
Only one server will be connected to the network at anyone time, it's not your traditional active/standby.
The active is connected to the network, if that fails, the standby will be physically connected to the network.
06-12-2013 06:23 AM
I agree with Bilal - when you plug in the new server it * should * do a gratuitous arp telling everyone to associate the IP address with its own MAC address. The switch and all devices attached to the network should then update their arp table accordingly. A static MAC entry would be no good as you would have to manually change the entry each time you had a switchover because the switch would have no knowledge of which entry it should be using at a given time.
This seems like an odd failover setup - what happens if it fails at 2am?
Do you not have the ability to do some form of adapter teaming on the server interfaces?
06-12-2013 06:35 AM
Hi
It is an odd setup agree, if it fails at 2am, there are ops guys that can re-patch.
The servers are located in different comms rooms, teaming can be done on the same server, but not on both?
We tested the fail over & the server would not connect unless the arp cache was cleared.
06-12-2013 06:44 AM
How long did you wait? If the server does not do a gratuitous arp then eventually the old entry would time out (after 5 minutes I think). You can verify this with "show mac-address table".
I should have said "network load balancing" rather than adapter teaming - it depends on what OS you are using on the server as to whether you can do this unless you invest in a physical load balancer.
06-12-2013 06:53 AM
to be fair it wasnt that long. 5 mins may be ok, the server is not critical.
I'll go back & test & time this.
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