![]() Instead, you can configure the gateway to provide a proxy ARP function so that it will reply to ARP requests with its own MAC address, as if the destination itself had responded. Obviously, the off-net destinations cannot answer because they never receive the ARP request broadcasts, these requests are not forwarded across subnets (blocked by routers, firewalls, or even switches). If the host is not so savvy about routing, it might still generate ARP requests for every off-net destination, hoping that someone will answer. ![]() Then packets can be relayed to the gateway directly without having to look for ARP entries for individual destinations. The host first sends an ARP request to find the gateway’s MAC address. If the host understands something about routing, it recognizes that all packets destined off-net must be sent to the gateway’s MAC address rather than the far end’s MAC address. However, if the far end is located on a different subnet, the host must rely on an intermediate system (a router, for example) to relay packets to and from that subnet.Ī host identifies its nearest router, aka default gateway or next hop, by its IP address. ![]() When a host must communicate with a device on its local subnet, it can generate an ARP request, wait for the ARP reply, and exchange packets directly. These are also commonly called first-hop redundancy protocols (FHRP) because the first router hop is given high availability. ![]() Virtual Router Redundancy Protocol (VRRP).Now we will focus on several approaches to providing router redundancy, including the following: These switches can also participate in routing protocols, just as traditional routers do. For high availability, multilayer switches should offer a means of preventing one switch (gateway) failure from isolating an entire VLAN. Multilayer switches can act as IP gateways for connected hosts by providing gateway addresses at VLAN SVIs and Layer 3 physical interfaces.
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