single IP bound to 2 server mac address's.

[seanbakers]

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?

[Bilal Nawaz]

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?

Please rate useful posts & remember to mark any solved questions as answered. Thank you.

[seanbakers]

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.

[mfurnival]

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?

[seanbakers]

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.

[mfurnival]

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.

[seanbakers]

to be fair it wasnt that long. 5 mins may be ok, the server is not critical.

I'll go back & test & time this.