Dual Homed Routing issue

[WillShakespeare]

All,

We have recently added a GB switch and connected extra GB NICs to each of our servers, so that our backup server can use this "network" exclusively for backups. Great idea in theory... but for some reason our Exchange falls over when I enable the NIC.

Our internal network is:
10.17.68.0

Our Backup network is:
10.11.68.0

Our International network (US) is:
10.17.69.0

Anyway, when the NICs are both enabled, we can see and ping both IPs on the Exchange server from any of our internal network 10.17.68.0

However, we can't ping any servers on 10.17.69.0 from the Exchange Server. This messes up our SMTP routing, and suddenly external emails are queued and aren't sent until I disable the new NIC 10.11.68.4

I wonder if anyone has any ideas that I could look into? Maybe someone who has done this before?

I suppose it may even be a DNS issue.

Will

 

[MarkArnold]

Re-post this question with your subnet masks please.

 

[WillShakespeare]

No probs... turns out is was the gateway that was the problem. As soon as I deleted the gateway entry all worked fine. Although I also changed the metrics to lower the priority of the backup NICs. The auto metric gave them a slightly higher priority to the main network.

Either of these may have contributed to solving this, or both, but after some discussions with some colleagues we figured it was the gateways that were causing the issue.

Thanks for reply though.

Will