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Walkthrough Wednesdays

Servers suddenly stop answering IP

We have an isolated LAN (02x switches 3750 with IP Base 12.2.25(SEE1)where soem of our servers are connected with a second lan interface that is used only for data backup. The switches configuration is default with only IP address at Int Vlan 1 for management.

And the problem is that three times (01 Unix and 02 Windows Servers) the servers stopped working and only solutions was rebooting them. Is ther some possible reason?




Are your two interfaces in seperate IP subnets?

Do both have default gateways assigned?

If so, don't add a default gateway to the interface for backup.

You may need to add a host or subnet route to the server to get to your backup server if it's not on the same subnet as the interface for backup.

You should probably also check whether the software you are running is compatible with such a configuration... some things aren't, or may require that you check your NIC bindings are in the correct order (i.e. 'live' NIC appears first).

Perhaps you should consider bonding the two interfaces into an active/passive fault tolerant setup (or an EtherChannel if you believe you need the bandwidth). If your backups are running at non-peak times, perhaps you don't need this type of setup at all?


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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!

Hi Aaron,

The servers have two NICs ans the second doesn't have default gateway. What is strange is that switch looses the NIC MAC Address from table. At the first time we rebooted the server and resolved but now it lost the communication again.



Hi Alex,

May I ask what servers you are using as you only mentioned you are using IP Telephony Servers.

If I understand correctly, you say you have configured seperate IP Addresses for the different NIC card in each of the servers.

If these are CallManager servers, you should note that it is Cisco recommendation to not do this. The 2nd NIC card should only be used for Network teaming. Refer to this previous thread :



P.s: HTAYQ - Hope that answers your qn. :D

Hi Yew,

The server that has lost communication again is a W2003 and uses the mais NIC for corporate LAN with many client-server applications and the second NIC (that is connected to 3750 of data backup network). The problem happens at data backup network switch and like I mencioned before, it stops answering and not eve the MAC address is detected by switch.

Have you ever seen that?



May I know what is this Server?

Is it a CCM, Unity server?

Have you checked the event viewer? Is there any errors shown?



It isn't IP Telephony related server, it is a database server and the second NIC is only for backup isolated LAN.



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