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Assign three/four different subnets to interface E0???

huytuan
Level 1
Level 1

Is it possible to allow three/four different subnet to an interface??? How??

At the moment:

interface Ethernet0

ip address 192.168.100.254 255.255.255.0

How do I allow three/four other subnet through this interface

How do I allow traffic from

193.168.100.0 255.255.255.0

194.168.100.0 255.255.255.0

203.174.156.192 255.255.255.224

to travel through the 192.168.100.254 255.255.255.0 interface??

2 Replies 2

Harold Ritter
Cisco Employee
Cisco Employee

I assume you are referring to directly connected hosts on these subnets off that same interface. Then you have to use secondary interface addresses as follow:

interface Ethernet0

ip address 192.168.100.254 255.255.255.0

ip address 193.168.100.0 255.255.255.0 secondary

ip address 194.168.100.0 255.255.255.0 secondary

ip address 203.174.156.192 255.255.255.224 secondary

Also, don't forget to include these addresses in your routing protocol.

Hope this help,

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

A minor correction to Hritter's post, the addresses specified should be ip addresses and not network addresses.

You can configure secondary ip addresses on all those subnets, on the same router interface.

int e0

ip add 192.168.100.254 255.255.255.0

ip add 193.168.100.254 255.255.255.0 secondary

ip add 194.168.100.254 255.255.255.0 secondary

ip add 203.174.156.222 255.255.255.224 secondary

This should do it.

You can include these addresses in your routing protocol, so that they get advertised to other routers. If you plan to use a router on any of these secondary networks, and run EIGRP or OSPF, it wont work, because neighbors are not formed on secondary networks on either protocols.

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus
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