Multiple default gateways for failover\redundancy

Answered Question
Aug 21st, 2007

Currently I have 1 defualt gateway that I route all my LAN traffic to the Internet.


Can I have a second one for failover\redundancy? How would the configuration work on my LAN machines ? Is it just a case of adding a second gateway on my devices' TCP\IP config ?

Thnx

Correct Answer by Richard Burts about 9 years 6 months ago

Ping


Yes to minimize the impact on users and prevent interruption it would be wise to use the existing address of the router as the shared address and to assign new addresses to the router interfaces.


HTH


Rick

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thomas.anthony Tue, 08/21/2007 - 08:59

You can?t have 2 GW configured on the PC, you will have to do redundancy at L3, what is the GW device you have is that Cisco Router / switch

p.choi Tue, 08/21/2007 - 09:02

The GW is a Cisco 2800 series router. How would I enable redundancy at L3 ?

Richard Burts Tue, 08/21/2007 - 09:01

Ping


I am not clear from your post quite what it is that you are attempting to accomplish. Is it a second gateway from the perspective of the PCs in your network (having a redundant router to establish connectivity if the primary router were to fail) or is it a second gateway for the router to use to have a redundant path to the outside?


If it is a second gateway for the PCs there is a simple answer: put the second router into the network and configure HSRP between the routers. With HSRP each router has its own physical interface address in the subnet and there is a shared address (or virtual address) that either router can use. You configure the PCs gateway address to be the shared HSRP address. In operation one of the routers becomes primary and uses the shared address and all the PCs send their traffic to the primary router. But if there is a problem with the primary router the standby router becomes active, takes over the shared address. This is quite transparent to the PCs. The PCs are still sending traffic to the same gateway address but now it happens to be on the second router rather than the first.


HTH


Rick

p.choi Tue, 08/21/2007 - 09:16

Rick,

thanks for the reply. With HSRP, I assume I would have to use the existing router's external interface ip address as the shared virtual address- if I wanted to minimize interruption to my users.



Correct Answer
Richard Burts Tue, 08/21/2007 - 09:18

Ping


Yes to minimize the impact on users and prevent interruption it would be wise to use the existing address of the router as the shared address and to assign new addresses to the router interfaces.


HTH


Rick

thomas.anthony Tue, 08/21/2007 - 09:13

When you said another GW is that you mean you have another router? If yes you many need to Run HSRP and use the VIP as the GW in the PC, if you have one router connecting to ISP and LAN it?s a single point of failur,

please provide the topology details for better solution

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