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Community Member

Dual NIC cards Traffic Flow

Hi,

Recently i have added Second NIC to our servers, the IP Address and Vlans are different for both network,

The problem starts when we pluggin the second NIC the entire server goes down becomes unstable.

Can anyone please help for both NIC's to be up and running without any descripancy.

Thanks

Tabrez

2 REPLIES
VIP Super Bronze

Re: Dual NIC cards Traffic Flow

Hello Tabrez,

If you have 2 NICs, then you should do NIC teaming and both NICs should be in the same subnet.  This way you have NIC redundency.

HTH

Reza

Hall of Fame Super Blue

Re: Dual NIC cards Traffic Flow

balbaletabrez wrote:

Hi,

Recently i have added Second NIC to our servers, the IP Address and Vlans are different for both network,

The problem starts when we pluggin the second NIC the entire server goes down becomes unstable.

Can anyone please help for both NIC's to be up and running without any descripancy.

Thanks

Tabrez

Tabrez

The issue is probably because you cannot use 2 default-routes on your server or rather if you have 2 default-routes you could see intermittent successful traffic. Solutions are -

1) As Reza said team the NICs together which would mean the 2 NICs would use the same IP/subnet mask

or

2)  If you want to have 2 NICs on 2 separate subnets choose one default-gateway for the server. If you then want traffic to go via the other NIC you need to add static routes to the server pointing to the other NICs default-gateway. An example might help -

NIC1 = 192.168.5.10/24   - defaullt-gateway = 192.168.5.1

NIC2 = 192.168.6.10/24  -  default-gateway = 192.168.6.1

lets say most traffic goes via 192.168.5.10 NIC1. So leave the default-gateway as 192.168.5.1

when you configure NIC2 do not fill in the default-gateway in the IP configuration.

Now lets say you want all traffic for 172.16.5.0/24 to go via NIC2 -

route add 172.16.5.0 mask 255.255.255.0  192.168.6.1    <--- note the route syntax will be dependant on the server OS

For every route you want to use NIC2 you will need a static route on the server.

Jon

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