Requirements for a floating route

[Spinzon84]

Hello guys,

Does anybody knows, What are the requirements to set up a floating route?

 I, mean, it has to be a physical connection for each route?

Below you can see about what i am talking about.

I got a connection between the router ant the switch, in the router gi0/1 are configured two sub interfaces with different ip segments and on the switch two vlan interfaces for each segment.

I have connectivity and my configuration is as follows:

ip route 0.0.0.0 0.0.0.0 190.242.129.233

ip route 0.0.0.0 0.0.0.0 200.116.209.105 5

When I shutdown the firts interface vlan (190.242.129.233), the second one doesnt go up.

Could you give some help with this? Please.

[balaji.bandi]

Can post the both the side config ?

BB

[Spinzon84]

Sure;

Router side:

interface GigabitEthernet0/1.666

encapsulation dot1Q 666

ip address 190.242.129.234 255.255.255.248

ip nat outside

!

interface GigabitEthernet0/1.667

encapsulation dot1Q 667

ip address 200.116.209.106 255.255.255.248

ip nat outside

ip nat inside source list NAT666 interface GigabitEthernet0/1.666 overload

ip nat inside source list NAT667 interface GigabitEthernet0/1.667 overload

ip classless

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.666

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.667 5

ip access-list extended NAT666

permit ip any any

ip access-list extended NAT667

permit ip any any

Switch Side:

interface GigabitEthernet0/1

description INTERNET_C&W

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface Vlan666

mac-address 0001.c958.3a01

ip address 190.242.129.233 255.255.255.248

!

interface Vlan667

mac-address 0001.c958.3a02

ip address 200.116.209.105 255.255.255.248

[Kaly_Narasingam]

Hi, Assume you have two different interfaces on router on the LAN side for each VLANs, please use the next hop interface number in both the static routes. Thx

[Spinzon84]

I did that, is not working. Is not changing to the other route, below you can see.

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.666

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.667 5

From the switch side:

Switch(config)#int vlan 666

Switch(config-if)#shut

Switch(config-if)#

%LINK-5-CHANGED: Interface Vlan666, changed state to administratively down

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan666, changed state to down

Routing table from router:

190.242.0.0/16 is variably subnetted, 2 subnets, 2 masks

C 190.242.129.232/29 is directly connected, GigabitEthernet0/1.666

L 190.242.129.234/32 is directly connected, GigabitEthernet0/1.666

200.116.209.0/24 is variably subnetted, 2 subnets, 2 masks

C 200.116.209.104/29 is directly connected, GigabitEthernet0/1.667

L 200.116.209.106/32 is directly connected, GigabitEthernet0/1.667

S* 0.0.0.0/0 is directly connected, GigabitEthernet0/1.666

doesnt change to the floating route to the gi0/1.667 interface

[chrihussey]

Are the static routes listed from the router or the switch? If they are from the switch the next hop specified needs to be the router, if it is the router, the next hop needs to be the switch.

[Spinzon84]

they are listed on the router side.

[chrihussey]

OK, if I understand things I think I see the problem.

Router and switch are trunked. Shutting the VLAN interface on the switch does not cause the router to switch its route to the other static. That is because shutting the VLAN interface does not cause the router's sub interface to fail. It stays up. So the route won't change.

If you were running a dynamic routing protocol (OSPF, EIGRP) on one VLAN and used a floating static on the other VLAN it would work.

If you had enough interfaces you could connect the router to the switch on two links and by failing one port it would cause the interface to go down and again the floating static would then work. However, shutting the VLAN interface would give you the same problem.

Also, on another note, the static routes in the router:

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.666

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1.667 5

these are incorrect in that you need to specifiy the next hop IP and not just an ethernet interface. The reason being is that on a multi access network (even if it was a /30), the router really doesn't know what the next hop would be. It has to make an ARP request for almost every packet it must send.

Hope this makes sense and helps.