Ethernet interface redundancy

Answered Question
Oct 9th, 2008

Hi,

Is it possible to use HSRP/VRRP internal one router if you want to have redundancy between two interfaces?

Our customer has router with two Ethernet interfaces.

This two interfaces are connected to two switches, there is also cross cable between the switches.

On the other side of the switches there are two other routers connected.

The customer will not use any routing protocols to get redundancy between the standalone router and the two separated routers.

Need some ideas how we can solved this.

//Niklas

I have this problem too.
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Correct Answer by Giuseppe Larosa about 8 years 2 months ago

Hello Niklas,

you can use IRB integrated routing and bridging: HSRP will not work as well explained by Jon.

bridge 1 protocol ieee

bridge 1 route ip

bridge 1 bridge ip

int eth0

no ip addr

bridge-group 1

int eth1

no ip addr

bridge-group 1

int bv1

ip address x.x.x.x

! this the layer3 interface

be aware that STP will block one link but it will be ready to be used if the first fails

you can uses static routes with IP next hops the ip addresses of the VIP of the HSRP made on the other two routers (on them you can they are two different boxes)

the other two routers will have static routes to the BVI ip address as next hop

be aware that until a router has an ARP entry for the ip next hop and its own interface is up the static route is considered valid

Hope to help

Giuseppe

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Jon Marshall Thu, 10/09/2008 - 09:27

HSRP will not work because you cannot assign 2 IP addresses out of the same subnet on 2 ethernet interfaces on the same router.

What type of redundancy are you looking for. If you cannot use routing protocols you could look into floating statics but it's very difficult to be more precise without more details.

Jon

yahoo2006 Thu, 10/09/2008 - 11:09

yes.

I think the best solution is to use floating static route

for example:

x.x.x.x 255.255.255.0 Fe1

x.x.x.x 255.255.255.0 Fe2 10

Correct Answer
Giuseppe Larosa Thu, 10/09/2008 - 12:32

Hello Niklas,

you can use IRB integrated routing and bridging: HSRP will not work as well explained by Jon.

bridge 1 protocol ieee

bridge 1 route ip

bridge 1 bridge ip

int eth0

no ip addr

bridge-group 1

int eth1

no ip addr

bridge-group 1

int bv1

ip address x.x.x.x

! this the layer3 interface

be aware that STP will block one link but it will be ready to be used if the first fails

you can uses static routes with IP next hops the ip addresses of the VIP of the HSRP made on the other two routers (on them you can they are two different boxes)

the other two routers will have static routes to the BVI ip address as next hop

be aware that until a router has an ARP entry for the ip next hop and its own interface is up the static route is considered valid

Hope to help

Giuseppe

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