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Routing Question

js358
Level 1
Level 1

Hello All:

The problem I'm having is on a linux box but it involves routing and there's no better place than here to get that topic addressed. Hoping someone can help out.

Linux 9.0 box 2 nics.

NIC1 - 10.0.2.150 gw 10.0.2.1

NIC2 - 209.178.228.150 gw 209.178.228.129

Nic2 is just an ethernet drop from our isp, going straight out to internet

Nics 2 connected to internal network whichis segmented by an internal router. The 10.0.2.1 gateway I am using is actually pointing to the router leading to the 2.x segment. There is a 4.x interface for entrance to 1.x segment.

No matter what I do, I cannot get all three segments seeing each other. Either 1x and 2x with no internet connectivity or 2x and internet with no 1x or vice versa. I cannot ger routing statements correct on the 2 Nics in the linux box to save my life.

Any help would be appreciated.

Thanks

5 Replies 5

Harold Ritter
Cisco Employee
Cisco Employee

You can't have two default gateway. The default route has to point toward your SP (209.178.228.129). You then need to have more specific routes (10.0.1.0/24 and 10.0.4.0/24) pointing to your internal router (10.0.2.1).

Hope this helps,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

sometimes I am confused about the two default gateway, most of time, it doesn't work.

there are 2 NICs in my PC, and both of them are dhcp client, and the 2 NICs can get IP from diffirent DHCP server and get 2 default gateway, and they worked.

Windows seems to do some type of load sharing when there are multiple default routes in the routing table. I haven't done any specific testing to attempt to narrow down how it behaves, but in my experience the behavior is inconsistent and unpredictable -- sometimes it load shares, sometimes it doesn't, and the failover mechanism (if there is one) isn't reliable.

The original posting is not reffering to a workstation with two default gateways but rather a Linux station being used as a router. In this scenario it doesn't make much sense to have a default gateway to the internal network.

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

deilert
Level 6
Level 6

I do not know the syntax for linux but you need to do something like this

nic 1

ip route 10.0.0.0 255.0.0.0 10.0.2.1

ip route 0.0.0.0 0.0.0.0 209.178.228.150

nic2

ip route 10.0.0.0 255.0.0.0 10.0.2.150

ip route 0.0.0.0 0.0.0.0 209.178.228.129