Proxy arp for redundancy 2 routers. CCNA?

[llukman.halimi]

I am studying redundancy for default gateway router failures for my CCNA exam. I am at the part of the book where it talks about Proxy ARP and how it responds to hosts that don't have a default gateway set up by responding with a Proxy Arp Reply. I know that once the host receives this reply it will by a reply with the proxy arp router's mac address on that host's subnet. And the host will basically now send all the packets it needs to send for that particular destination subnet that is outside it's subnet by using that proxy ARP's router mac address.

I get all that but my confusion is in the book there are 2 router's which are both enabled for proxy ARP what I want to know is which router is responding for the arp requests and which one is standing by incase the other router fails and how do these router's know when one fails?

I have attached the page that I am currently on as a reference to what I am asking on here. By the way the picture illustration of the network design there is no default gateway for the router configured it's just that picture that has made that mistake.

[Philip D'Ath]

Both routers would send proxy-arp replies.

[Matt Glosson]

How would that not result in an IP conflict? For example, let's say that the 10.0.0.1/24 router's MAC address is 00-00-0c-00-00-01 and the 10.0.0.2/24 router's MAC address is 00-00-0c-00-00-02, and proxy-arp is enabled on both. Behind those routers there is a host, 10.1.1.3/24.

If I'm 10.0.0.3 and I send an ARP request for 10.1.1.3, will not both 10.0.0.1 and 10.0.0.2 reply with their own MAC addresses and make it seem like 10.1.1.3 has two MAC addresses (a.k.a., an IP conflict)? Maybe it doesn't matter--the device issuing the ARP request will just accept whichever one comes in second... thoughts?

[paul driver]

Hello

As both routers RTR1- RTR2 are on the same subnet the router which knows how to reach the remote network will reply with it own mac-address for that destination.

On the other hand lets say RTR1 is you gateway and it replies first and then sees a better path via RTR2 for your destination as such it can redirect your host with any further request towards RTR2  - This is called icmp redirects

res

Paul