3com 5500-ei pwr Instruccion De Instalación

 

3-2 

Host A and Host D are on different sub networks. When Host A (192.168.0.22/16) needs to send 

packets to Host D (192.168.1.30/16), because the mask of the two hosts are both 16 bits, Host A 

regards Host D to be on its directly connected sub network, and thus Host A will broadcast an ARP 

request to request the MAC address of Host D.  

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When the common proxy ARP feature is not enabled on the switch, because Host A and Host D are 

in different VLANs, the ARP request sent by Host A cannot reach Host D, and the two hosts cannot 

communicate.  

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With common proxy ARP enabled on the switch, when VLAN-interface 3 receives the ARP request, 

if the switch finds a route to the destination IP address (encapsulated in the ARP request) in the 

routing table, the switch sends host A the MAC address of VLAN-interface 3 in an ARP response 

(with the source IP address being the destination IP address of the ARP request). After receiving 

the ARP response, Host A creates an ARP entry, in which the destination IP address is the IP 

address of Host D (192.168.1.30/16), and the MAC address is that of VLAN-interface 3. The 

following packets sent from Host A to Host D will all be sent to VLAN-interface 3 of the switch, and 

then the switch forwards the packets in Layer 3 to Host D, so as to realize the Layer 3 connectivity 

between Host A and Host D. 

If IP hosts on a network have no default gateway configured or have no routing capability, you can use 

common proxy ARP to address this issue. 

The following gives a local proxy ARP application scenario. Host A and Host B belong to the same 

VLAN, and they respectively connect to Switch B’ Layer 2 ports Ethernet 1/0/2 and Ethernet 1/0/3, 

which are isolated at Layer 2. To allow the two hosts to communicate at Layer 3, you can enable local 

proxy ARP on Switch A. 

Figure 3-2 Local proxy ARP application 

 

 

In one of the following cases, you need to enable local proxy ARP: 

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Hosts connecting to different isolated Layer 2 ports in the same VLAN need to communicate at 

Layer 3. 

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After Isolate-user-VLAN function is configured on a device attached to a S5500-EI series Ethernet 

switch, hosts belonging to different secondary VLANs need to communicate at Layer 3. 

Follow these steps to configure proxy ARP: 

Enter system view 

system-view 

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