Two networks out one interface. 3

[rswift]

IP addresses changed from original....

I am trying to route two internal IP networks (10.38.7 and 10.38.8) out the same interface. What is the best way to do this?

interface GigabitEthernet0/0
description OUTSIDE INTERFACE (Untrusted)$ETH-WAN$
ip address 79.289.54.18 255.255.255.224
ip nbar protocol-discovery
ip flow ingress
ip flow egress
no ip mroute-cache
duplex auto
speed auto
no cdp enable
crypto map to_vpn
!
interface GigabitEthernet0/1
description INSIDE INTERFACE (Trusted)
ip address 10.38.7.1 255.255.255.0
ip nat inside
ip virtual-reassembly
duplex auto
speed auto
!

 

[VinceWhirlwind]

Either:

1/ ip address secondary

or

2/ remove the IP address from the interface and configure it as a .1q trunk and then configure subinterfaces and assign the addresses to that along with a VLAN ID for each.

 

[hummer3331973]

Hi Vince-

I would like to use a secondary IP add as specified in your post. I will then have a router with 2 IP address on one interface:

interface FastEthernet0/1
description
ip address 1.2.3.4 255.255.255.248
ip address 2.3.4.5 255.255.255.252 secondary

But on my switch that's connected to this router, is it ok to run two different subnets? I haven't tried it before but what will be the problem on doing this?

Thanks.

 

[cameramonkey]

we do secondary IPs at our office on a pair of 1841s that do failover between a T1 and a wifi backhaul. Its no biggie. your subnet 1 devices will ignore the traffic on your subnet 2 devices and vice versa.

 

[hummer3331973]

Ok thanks for the info. I'm thinking of doing this instead of creating VLANs since it's only a 16 port switch.

 

[VinceWhirlwind]

Personally, I really, really hate multiple subnets on the same broadcast domain. It just seems such an inelegant way of doing things.

BUT, if it's for a tiny environment, as you describe, then perhaps adding VLANs would unnecessarily complicate future support of the network - "IP address secondary" would be a bit easier to understand that dot1q subinterfaces, and reduce the amount of config required on the switch.

 

[rswift]

I did setup vlans and used the dot1q method. Everything is working well and thank you all for your input.