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New Member

redundacy

Hi

Does anybody know how to configure router to have 2 uplinks in order to have redundancy? I can't configure HSRP because router rejects two interfaces to have IP address from the same subnet.

I need to have one interface active and second standby (second interface activates only when first fails).

thanks in advance

2 ACCEPTED SOLUTIONS

Accepted Solutions
New Member

Re: redundacy

Hi

You can configure this as follows:

int fa0/0

backup interface fa0/1

ip add a.b.c.d e.f.g.h

int fa0/1

ip add a.b.c.d e.f.g.h

HTH

Hitesh / Mohit

Hall of Fame Super Silver

Re: redundacy

ali

I think that you misunderstand what I was saying. STP operates at layer 2 and does not operate at layer 3. My suggestion was that if they really want 2 Ethernet interfaces to back each other up that they configure bridging on both of the Ethernet interfaces. Bridging is a layer 2 process and uses STP to detect loops. Then if they configure IRB (including configuration of the BVI) they can route IP while bridging on the physical interfaces.

If you want information about IRB and how to configure the BVI this link should get you started:

http://www.cisco.com/en/US/customer/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800ca766.html#wp1002234

HTH

Rick

5 REPLIES
Hall of Fame Super Silver

Re: redundacy

antonio

If you really want to have two Ethernet intefaces in the same subnet with one active and one backup then you could configure Integrated Routing and Bridging. In IRB you configure a BVI (Bridged Virtual Interface) on which you configure the IP address. And you configure the two Ethernets with bridging linked to the BVI. With briding configured Spanning Tree will put one interface into blocking mode and one interface in forwarding mode. If the primary interface fails Spanning Tree will converge and bring the other interface from blocking mode to forwarding mode.

HTH

Rick

New Member

Re: redundacy

Hi Rick!

can u list a simple config for the bvi;and how to use stp in the L3

10xs

Hall of Fame Super Silver

Re: redundacy

ali

I think that you misunderstand what I was saying. STP operates at layer 2 and does not operate at layer 3. My suggestion was that if they really want 2 Ethernet interfaces to back each other up that they configure bridging on both of the Ethernet interfaces. Bridging is a layer 2 process and uses STP to detect loops. Then if they configure IRB (including configuration of the BVI) they can route IP while bridging on the physical interfaces.

If you want information about IRB and how to configure the BVI this link should get you started:

http://www.cisco.com/en/US/customer/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800ca766.html#wp1002234

HTH

Rick

New Member

Re: redundacy

Hi

You can configure this as follows:

int fa0/0

backup interface fa0/1

ip add a.b.c.d e.f.g.h

int fa0/1

ip add a.b.c.d e.f.g.h

HTH

Hitesh / Mohit

Re: redundacy

Hi,

It would be better to go for a routing protocol with the provider , so that you can always set some preference for a route . Eg : Go for bgp with provider , receive a default from the provider , set a preference via one link ) and in case of failure of one , default would prefer the other and similarly the ISP would also set a preference for the return traffic.

Hope this helps

regards

vanesh k

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