Redirect checking in a network device

Abstract

A network device for performing redirect checking includes an input device and processing logic. The input device receives a data packet on a first one of a number of interfaces. The data packet includes source and destination addresses. The processing logic assigns an incoming interface to the data packet and generates forwarding information identifying a next hop for the data packet. The processing logic also identifies an outgoing interface based on the next hop and determines whether the incoming interface index is equal to the outgoing interface index. The processing logic also determines whether the data packet originated from a station that is part of the same subnet as the next hop. When both of these conditions are met, the processing logic generates a redirect message.

1 - 27 . (canceled) 
     
     
         28 . A method comprising:
 receiving a packet including a source address;   generating a hash value using a portion of the source address; and   determining whether to transmit a redirect message based on a first interface on which the packet is received, a second interface on which the packet is to be transmitted, the generated hash value, and a stored hash value.   
     
     
         29 . The method of  claim 28 , further comprising:
 comparing the generated hash value to the stored hash value.   
     
     
         30 . The method of  claim 29 , where the determining whether to transmit the redirect message is based on the comparison of the generated hash value to the stored hash value. 
     
     
         31 . The method of  claim 28 , further comprising:
 comparing the first interface to the second interface.   
     
     
         32 . The method of  claim 31 , where the determining whether to transmit the redirect message is based on the comparison of the first interface to the second interface. 
     
     
         33 . The method of  claim 28 , further comprising:
 comparing the generated hash value to the stored hash value; and   comparing the first interface to the second interface.   
     
     
         34 . The method of  claim 33 , where the determining whether to transmit the redirect message is based on the comparison of the generated hash value to the stored hash value and the comparison of the first interface to the second interface. 
     
     
         35 . The method of  claim 34 , where, when the first interface and the second interface are the same and the generated hash value equals the stored hash value, the method further comprises:
 indicating that a redirect message is required; and   transmitting the redirect message to a host processor.   
     
     
         36 . The method of  claim 28 , where the hash value is associated with an Internet Protocol source address of the packet. 
     
     
         37 . The method of  claim 36 , further comprising:
 generating the hash value using a predetermined number of significant bits of the IP source address.   
     
     
         38 . A device, comprising:
 an input device to receive a data packet, including a source address, from an interface, the input device including a memory containing instructions that, when executed by one or more processors, cause the one or more processors to:
 generate forwarding information identifying a next hop for the data packet; 
 determine whether an index of the interface is the same as an index of an interface on which the data packet is to be forwarded; 
 determine whether a device originating the data packet belongs to a subnet of the next hop; 
 generate a redirect message based on both determinations; and 
 transmit the generated redirect message. 
   
     
     
         39 . The device of  claim 38 , where the redirect message includes next hop information for another data packet having a same destination address as the data packet. 
     
     
         40 . The device of  claim 38 , where, when determining whether the device belongs to the same subnet as the next hop, the one or more processors are to:
 identify an incoming index associated with the interface;   identify an outgoing interface index associated with the next hop; and   compare the incoming index to the outgoing index.   
     
     
         41 . The device of  claim 38 , where the source address includes a number of bits and, when determining whether the device belongs to the same subnet as the next hop, the one or more processors are to:
 select a portion of the number of bits of the source address of the data packet; and   generate a hash value using a hash function and the selected portion of the number bits.   
     
     
         42 . The device of  claim 41 , where the one or more processors are further to:
 compare the generated hash value to a stored hash value; and   determine that the device belongs to a same subnet as the next hop when the generated hash value equals the stored hash value.   
     
     
         43 . A device, comprising:
 an input device to receive a data packet, including a source address, from an interface, the input device including a memory containing instructions that, when executed by one or more processors, cause the one or more processors to:
 generate forwarding information identifying a next hop for the data packet; 
 determine whether the data packet is to be forwarded via the interface at which the data packet was received; 
 generate a hash value of the source address; 
 compare the generated hash value to a stored hash value; and 
 forward a message to a host processor indicating that a redirect message, associated with the received data packet, is required when:
 the data packet is to be forwarded via the interface at which the data packet was received, and 
 the generated hash value equals the stored hash value. 
 
   
     
     
         44 . The device of  claim 43 , where, when generating the hash value of the source address, the one or more processors are to:
 generate the hash value using a predetermined number of significant bits of the source address.   
     
     
         45 . The device of  claim 43 , where, when determining whether the data packet is to be forwarded via the interface at which the data packet was received, the one or more processors are to:
 compare an incoming interface index and an outgoing interface index.   
     
     
         46 . The device of  claim 43 , where the redirect information includes at least one of:
 an outgoing interface value or a prefix length value associated with the hash value.   
     
     
         47 . The device of  claim 43 , where the host processor is to:
 receive the message from the one or more processors;   generate a redirect message; and   transmit the redirect message to a device originating the data packet.