Proxy ARP - quick review

Proxy arp is a feature that is recommended to disable if you have a router facing interne.

 

and better to enable only on interfaces that are working in an internal LAN.

 

 

#ip proxy-arp  [will make the router advertise itself "mac address" as the mac address of the destination needed instead of the real device]

 Disable ARP proxy globally is 

# ip arp proxy disable and under interface is 

#no ip proxy-arp 

Ok, so now what is the proxy ARP? 

It’s a feature that is enabled by default on Routers that enabled the router to direct the traffic for

network that doesn’t have Reach-ability to destination when the router interface have the route to it.

If you disable the Proxy-ARP on interface the router 1 will not be able to reach router6 loop-back interface, the reason is it won't be able to get L2 mac address Of the destination, [the reason is using ip route to exit interface of the router instead of IP address of next hop]

if you enable debug for it #debug IP packets you will see encapsulation error,

which means router failed to build Layer 2 frame

The solution

 is to

• hard-code the ARP and mac address for the destination then it will be reachable.
• Or enable the proxy ARPon interface
• Use IP route to next hop address instead of pointing to the exit interface