supported only for the IP address belongs to the received interface IP network. Proxy ARP is notsupported if the ARP requested IP address is different from the received interface IP subnet. For example,if VLAN 100 and 200 are configured on the VLT peers, and if the VLAN 100 IP address is configured as10.1.1.0/24 and the VLAN 200 IP address is configured as 20.1.1.0/24, the proxy ARP is not performed ifthe VLT node receives an ARP request for 20.1.1.0/24 on VLAN 100.Working of Proxy ARP for VLT Peer NodesProxy ARP is enabled only when peer routing is enabled on both the VLT peers. If peer routing is disabledon one of the VLT peers, proxy ARP is not performed when the ICL link goes down. Proxy ARP isperformed only when the VLT peer's MAC address is installed in the database. Proxy ARP is stopped whenthe VLT peer's MAC address is removed from the ARP database because of the peer routing timer expiry.The source hardware address in the ARP response contains the VLT peer MAC address. Proxy ARP issupported for both unicast and broadcast ARP requests. Control packets, other than ARP requestsdestined for the VLT peers that reach the undesired and incorrect VLT node, are dropped if the ICL link isdown. Further processing is not done on these control packets. The VLT node does not perform anyaction if it receives gratuitous ARP requests for the VLT peer IP address. Proxy ARP is also supported onsecondary VLANs. When the ICL link or peer is down, and the ARP request for a private VLAN IP addressreaches the wrong peer, then the wrong peer responds to the ARP request with the peer MAC address.The IP address of the VLT node VLAN interface is synchronized with the VLT peer over ICL when the VLTpeers are up. Whenever an IP address is added or deleted, this updated information is synchronized withthe VLT peer. IP address synchronization occurs regardless of the VLAN administrative state. IP addressaddition and deletion serve as the trigger events for synchronization. When a VLAN state is down, the VLTpeer might perform a proxy ARP operation for the IP addresses of that VLAN interface.VLT nodes start performing Proxy ARP when the ICL link goes down. When the VLT peer comes up, proxyARP will be stopped for the peer VLT IP addresses. When the peer node is rebooted, the IP addresssynchronized with the peer is not flushed. Peer down events cause the proxy ARP to commence.When a VLT node detects peer up, it will not perform proxy ARP for the peer IP addresses. IP addresssynchronization occurs again between the VLT peers.Proxy ARP is enabled only if peer routing is enabled on both the VLT peers. If you disable peer routing byusing the no peer-routingcommand in VLT DOMAIN node, a notification is sent to the VLT peer todisable the proxy ARP. If peer routing is disabled when ICL link is down, a notification is not sent to theVLT peer and in such a case, the VLT peer does not disable the proxy ARP operation.When the VLT domain is removed on one of the VLT nodes, the peer routing configuration removal willbe notified to the peer. In this case VLT peer node disables the proxy ARP. When the ICL link is removedon one of the VLT nodes by using the no peer-link command, the ICL down event is triggered on theother VLT node, which in turn starts the proxy ARP application. The VLT node, where the ICL link isdeleted, flushes the peer IP addresses and does not perform proxy ARP for the additional LAG hashedARP requests.894 Virtual Link Trunking (VLT)
