Proxy ARP

When switch doesn’t have a routing protocol enabled to be able to access other subnet’s then Proxy ARP can be used to reach these hosts. The way it does this is by treating all IP addresses (regardless of the mask configured on the interface) as being a part of the local link and therefore will ARP for it. A router on the link also configured for proxy ARP can then respond with its MAC and will forward traffic for the switch. By default proxy ARP is enabled.

To configure Proxy ARP (if disabled)

Switch(config)#int vlan 100
Switch(config-if)#ip proxy-arp

Note: same for the upstream router.

Can see if it’s enabled by doing a “show ip interface”

Switch(config)#do sh ip int vlan 100
Vlan100 is up, line protocol is up
Internet address is
< omitted for brevity>
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
Security level is default
< omitted for brevity>


About ccie4all
Hello, and welcome to the first post of my CCIE blog This blog has got one simple goal and that is to improve our skills in Cisco Networking field so we can become best engineers on a job market. Wordpress Blog information about the changes made to Gns3 BGP , MPLS and R&S CCIE labs. In order to access and download all provided materials and receive important updates from Gns3 BGP , MPLS and R&S CCIE labs under GNS3 tab in the main header please go ahead and subscribe to ! All other posts have not been affected and can be accessed at any given time. Enjoy ! Tom

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