JPH08251227A - Routing table, method for preparing the table and routing table generating device applying the them - Google Patents

Abstract

PURPOSE: To make possible intermittent usage even when transfer to a specified transfer destination candidate address is disabled by preparing the routing table corresponding to the number of transfer destination candidate address allowing the second transfer destination candidate to be hopped. CONSTITUTION: A discrimination part 52 compares the presence/absence of first transfer destination candidate addresses as one part of the transfer destination candidate addresses, the number of packets for RIP to be hopped and the number of parts corresponding to a table to be hopped. Then, a first candidate comparing means 521 selects the first transfer destination candidate addresses and its number to be hopped. Besides, the presence/absence of second transfer destination addresses as the other part of transfer destination candidate addresses, the number of packets for RIP to be hopped and the number of parts corresponding to the table to be hopped are compared. Then, a second candidate comparing means 522 selects the second transfer destination candidate addresses and its number to be hopped. Corresponding to these results, a routing table 100 is generated and according to a control part 53, a transmission part 54 performs packet transmission through a transmitting means 542 while referring to the contents in the table 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly directed to Routing Information Protocol (Routing).
Information Protocol / Below, RI
(Referred to as “P”), a routing table created based on the number of hops of the transfer destination candidate addresses permitted up to the second transfer destination candidate, a method of creating the routing table, and a routing table creation device to which the method is applied.

[0002]

2. Description of the Related Art Conventionally, as a method of creating a routing table of this kind, in order to autonomously create a routing table of the shortest route, for example, as shown in RFC1058 (standard), RIP packets are periodically sent. When the received RIP packet is broadcasted and new address information is present, unconditional addition processing is performed on the table. However, when the received RIP packet already has address information, the hop count is compared and the received RIP packet of the received RIP packet is compared. The rewriting process is performed only when the number of hops is less than the existing number of hops, and the packet is transmitted based on the routing table. Here, when the conventional route cannot be used due to a change in the network topology, the corresponding address information is deleted from the routing table and a new routing table is created.

FIG. 12 is a block diagram showing the basic configuration of a conventional routing table creating device. This routing table creating device determines a routing table 10 having a destination network address, a transfer destination candidate address, and its hop count, a receiving unit 1 that receives a RIP packet, a transfer destination candidate address, and its hop count. It comprises a unit 2, a control unit 3 for rewriting or adding the routing table 10 and a process for discarding unnecessary packets, and a transmitting unit 4 for transmitting packets while referring to the routing table 10 according to the control unit 3. To be done. Of these, the receiving unit 1 is the receiving means 1
1 and a selection means 12, and the determination unit 2 has a comparison means 21.
Is provided. Further, the control unit 3 includes a routing table control unit 31 and a discarding unit 32, and the transmission unit 4 has a reference unit 4
1 and transmitting means 42.

FIG. 13 is a flow chart showing the operation processing of the routing table creating method by the routing table creating device. Here, first, when a received packet is received via the receiving unit 11 of the receiving unit 1, the selecting unit 12 determines whether or not the packet is a RIP packet and transfers the selected RIP packet (step S1) is performed. Next, the determination unit 2 determines the presence / absence of the transfer destination candidate address in the routing table 10 based on whether or not the transfer destination candidate address already exists (step S2).
If there is, the comparison means 21 further compares the hop count of the RIP packet and the hop count of the transfer destination candidate address to determine whether the hop count of the RIP packet is greater than or equal to the hop count of the transfer destination candidate address. (Step S3).

Continuing on, if the hop count of the RIP packet is less than the hop count of the transfer destination candidate address, the control unit 3 determines whether the previous transfer destination candidate address already exists or not (step S2). Similarly, the routing table control means 31 rewrites the routing table 10 (step S5). If the number of hops of the RIP packet is equal to or larger than the number of hops of the transfer destination candidate address, the routing table control means 31 discards the means 32. The packet is considered to be an unnecessary packet via (1) and is discarded (step S4). Incidentally, in the transmission unit 4, the contents of the routing table 10 are referred to by the reference unit 41 according to the control unit 3, and the packet is transmitted via the transmission unit 42.

FIG. 14 shows the structure of the RIP packet, and FIG. 15 shows the structure of the routing table 10. Here, the RIP packet has a configuration in which a network address 301 is added to the head, and a hop number 302 and a reception address 303 are added.
Further, the routing table 10 has a structure in which a transfer destination candidate address 402 and a hop count 403 are added to the destination network address 401 at the head.

Correspondence between the RIP packet and the routing table shown in FIGS. 14 and 15 and the above-mentioned operation processing will be described. First, in step S1, the selection means 12
Then, the RIP packet is transferred, and in step S2, the presence / absence of the network address 301 of the RIP packet in the target network address 401 of the routing table 10 is confirmed by the comparison means 21, and if there is, it is transferred to the routing table control means 31. If there is not, it is transferred to the comparison means 21. Next, in step S3, the comparison means 2
1 compares the hop count 302 of the RIP packet with the hop count 403 of the transfer destination candidate address 402. If the hop count 302 is larger, the hop count 302 is transferred to the discarding unit 32.
If the number of hops 302 is smaller, it is transferred to the routing table control means 31.

Incidentally, as a related technique for creating a routing table based on the number of hops of a transfer destination candidate address in packet communication, Japanese Patent Laid-Open No. 63-207242 has been proposed.
Examples include a routing control system of a packet switching network disclosed in Japanese Patent Laid-Open No. 3-88533, a selective routing system disclosed in Japanese Patent Laid-Open No. 3-88533, and a distributed communication network disclosed in Japanese Patent Laid-Open No. 3-136433.

[0009]

In the case of the routing table creating method by the table creating device described above, since only the first candidate routing table is provided for the address information of each transfer destination, the route is changed due to the change of the network topology. When it becomes unusable, it is necessary to delete the corresponding address information from the routing table and recreate a new routing table, which takes too much time.

The present invention has been made to solve such a problem, and its technical problem is to transfer after creating a new routing table when transmission cannot be performed due to transfer to a specific transfer destination candidate address. (EN) Provided are a routing table capable of continuously performing routing without restarting the routing table, a method of creating the routing table, and a routing table creation device to which the routing table is applied.

[0011]

According to the present invention, a RIP
The first transfer destination candidate address and the number of hops of the first transfer destination candidate address as a part of the transfer destination candidate address and the second transfer destination candidate address and the second as the other part of the transfer destination candidate address. 2 is a routing table having two hop numbers of transfer destination candidate addresses, wherein the first transfer destination candidate address and the hop number of the first transfer destination candidate address are the presence or absence of the first transfer destination candidate address. RI
The second transfer destination candidate address and the hop count of the second transfer destination candidate address are selected based on the comparison result of the hop count of the P packet and the hop count of the table corresponding portion. A routing table selected based on the presence / absence of the second transfer destination candidate address, the hop count of the RIP packet, and the result of comparing the hop count of the corresponding portion of the table is obtained.

On the other hand, according to the present invention, in the method of creating the routing table using the transfer destination candidate address and the number of hops of the transfer destination candidate address by using RIP, the first destination address is used as a part of the transfer destination candidate address. Of the first transfer destination candidate address and the hop of the first transfer destination candidate address based on the result of the comparison of the presence or absence of the transfer destination candidate address of the RIP packet and the size of the hop number of the table corresponding portion. The first candidate selection step of selecting the number, the presence or absence of the second transfer destination candidate address as the other part of the transfer destination candidate address, the result of comparing the hop count of the RIP packet and the hop count of the table corresponding part. And a second candidate selecting step for selecting the second transfer destination candidate address and the hop number of the second transfer destination candidate address based on How to create a Buru is obtained.

On the other hand, according to the present invention, a routing including a transfer destination candidate address by using RIP and a hop number of the transfer destination candidate address, and a determination unit for determining the transfer destination candidate address and the hop number In the table creation device, the determination unit is based on the result of comparing the presence or absence of the first transfer destination candidate address as a part of the transfer destination candidate address, the hop count of the RIP packet, and the hop count of the corresponding portion of the table. The first transfer destination candidate address and first candidate comparison means for selecting the number of hops of the first transfer destination candidate address, the presence or absence of a second transfer destination candidate address as another part of the transfer destination candidate address, and RI.
Second candidate comparison for selecting the second transfer destination candidate address and the hop count of the second transfer destination candidate address based on the result of comparing the hop count of the P packet and the hop count of the corresponding portion of the table The routing table includes a first transfer destination candidate address and the number of hops of the first transfer destination candidate address, and a second transfer destination candidate address and the number of hops of the second transfer destination candidate address. A routing table creation device having the same can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A routing table, a method for creating the same, and a routing table creating apparatus to which the present invention is applied will be described below in detail with reference to the drawings.

First, the outline of the method of creating the routing table of the present invention will be briefly described. This method of creating a routing table is such that when a routing table is created based on the number of hops of a transfer destination candidate address using RIP, the presence or absence of the first transfer destination candidate address as a part of the transfer destination candidate address and RIP A first candidate selection step of selecting a first transfer destination candidate address and a hop count of the first transfer destination candidate address based on a result of comparing the number of hops of the packet and the size of the number of hops of the corresponding portion of the table; , A second transfer destination candidate address based on the result of comparing the presence or absence of a second transfer destination candidate address as the other part of the transfer destination candidate address, the hop count of the RIP packet, and the hop count of the corresponding portion of the table. And a second candidate selection step of selecting the number of hops of the second transfer destination candidate address.

FIG. 1 is a block diagram showing the basic configuration of a routing table creating apparatus to which this routing table creating method is applied.

This routing table creating device has a destination network address, a first network address and a first network address, as will be described later in detail.
Of the transfer destination candidate address and the number of hops thereof, the second transfer destination candidate address and the number of hops thereof, the receiving unit 51 for receiving the RIP packet, each transfer destination candidate address and the number of hops thereof. Determining unit 52 for determining the routing table 10
The control unit 53 performs a process of rewriting or adding 0 and a process of discarding unnecessary packets, and a transmission unit 54 that transmits packets while referring to the routing table 100 according to the control unit 53. Of these, the receiving unit 5
1 includes a receiving unit 511 and a selecting unit 512, and the determining unit 52 includes a first candidate comparing unit 521 and a second candidate comparing unit 522. Further, the control unit 53 includes a routing table control unit 531 and a discarding unit 532, and the transmission unit 5
4 includes a reference unit 541 and a transmission unit 542.

That is, as compared with the conventional device shown in FIG. 12, in this routing table creating device, the determining unit 52 determines whether or not the first transfer destination candidate address exists as a part of the transfer destination candidate address and the hop of the RIP packet. Number and the first candidate comparing means 521 for selecting the first transfer destination candidate address and the number of hops thereof based on the result of comparison of the hop counts of the corresponding parts of the table, and the second as another part of the transfer destination candidate address. Second candidate comparison means for selecting the second transfer destination candidate address and its hop count based on the presence or absence of the transfer destination candidate address and the result of comparing the hop count of the RIP packet and the hop count of the corresponding portion of the table. 522 and the routing table 100 created by this is the same as the above-mentioned first transfer destination candidate address and its address. Having number-flop and a second transfer destination candidate address and the number of that hop.

FIG. 2 is a flow chart showing the operation processing of the routing table creating method by this routing table creating apparatus. Here, first, the receiving unit 5
When the received packet is received through the first receiving unit 511, the selecting unit 512 determines whether or not the packet is the RIP packet and transfers the selected RIP packet (step S1). Next, in the determination unit 52, the first candidate comparison unit 521 determines the presence / absence of the first transfer destination candidate address in the routing table 100 based on whether or not the first transfer destination candidate address already exists (step S2). In this case, the comparison unit 521 further determines whether the hop count of the RIP packet and the hop count of the first transfer destination candidate address is greater than or equal to the hop count of the RIP packet is greater than or equal to the hop count of the first transfer destination candidate address. Then, a comparison judgment is made (step S3).

Subsequently, the judging unit 52 compares the second candidate if the hop count of the RIP packet is equal to or larger than the hop count of the first transfer destination candidate address (step S3). The presence / absence of the second transfer destination candidate address in the routing table 100 is determined by the means 522 based on whether or not the second transfer destination candidate address already exists (step S4). If there is, the comparing means 522 further determines the RIP packet. Is compared with the hop count of the second transfer destination candidate address depending on whether or not the hop count of the RIP packet is greater than or equal to the hop count of the second transfer destination candidate address (step S5).

Further, in the control unit 53, if the hop count of the RIP packet is less than the hop count in the comparison judgment (step S5) as to whether the hop count is equal to or larger than the hop count of the second transfer destination candidate address, the first first If it is not determined whether the transfer destination candidate address already exists (step S2), it is determined whether the hop number of the RIP packet is equal to or more than the hop number of the first transfer destination candidate address (step S3). Similar to the case where the number is less than the number and the case where it is not determined whether the second transfer destination candidate address already exists (step S4), the routing table control means 531 rewrites the routing table 100 (step S7). But R
If the number of hops of the IP packet is equal to or larger than the number of hops of the second transfer destination candidate address, the routing table control unit 531 treats it as an unnecessary packet through the discarding unit 532 and discards it (step S6). Incidentally, in the transmission unit 54, the contents of the routing table 100 are referred to by the reference unit 541 according to the control unit 53, and the packet is transmitted via the transmission unit 542.

FIG. 3 shows the structure of the routing table 100. Here, in the routing table 100, the first transfer destination candidate address 702 and the number of hops 70 of the first transfer destination address 701 start
3 and the second transfer destination candidate address 704 and the number of hops 705 thereof are added.

Correspondence between the routing table 100 shown in FIG. 3 and the above-mentioned operation processing will be described. First, in step S1, the RIP packet is transferred from the selection unit 512, and in step S2, the first candidate comparison unit 521 of the determination unit 52 reads the network address of the RIP packet and compares it with the network address of the existing routing table 100. The presence / absence of a new network address is determined, and if there is a new network address, the routing table control means 531 of the control unit 53.
Forward to R, if there is no new network address
The hop count of the IP packet is read, and the first transfer destination candidate address 702 of the existing routing table 100 is read.
Compare with the number of hops.

Next, in step S3, when the hop count of the RIP packet is less than the hop count of the already existing first transfer destination candidate address 702, it is transferred to the routing table control means 531 and the hop of the RIP packet is transferred. If the number is equal to or larger than the number of hops of the first transfer destination candidate address 702, the number is transferred to the second candidate comparison means 522. In step S4, the second candidate comparison unit 522 confirms the presence or absence of the second transfer destination candidate address 704, and the hop count of the RIP packet and the existing routing table 100.
The second transfer destination candidate address 704 is compared with the hop count. Next, in step S5, when the number of hops of the RIP packet is less than the hop of the second transfer destination candidate address 704, the routing table control means 5
If the hop count of the RIP packet is equal to or larger than the hop count of the already existing second transfer destination candidate address 704, the packet is transferred to the discarding unit 532 of the control unit 53.

Further, when the routing table control means 531 in the control unit 53 transfers the RIP packet from the first candidate comparison unit 521 of the determination unit 52 in step S7, the network address of the RIP packet is shown in FIG. The destination network address 701 of the table 100 is written (rewritten), the hop number of the RIP packet is written to the hop number 703 of the routing table 100, and the received address of the RIP packet is the first transfer destination candidate address 702 of the routing table 100. To the second transfer destination candidate address 704 and the hop count 705, and the already existing first transfer destination candidate address 702 and hop count 703 are written to the second transfer destination candidate address 704 and the hop count 705. When the RIP packet is transferred from the second candidate comparison unit 522 of the determination unit 52, the network address of the RIP packet is written in the second transfer destination candidate address 704 and its hop count 705 of the routing table 100 in step S7. Further, in step S6, the discarding means 53
2 discards the RIP packet transferred from the second candidate comparison unit 522 of the determination unit 52.

Incidentally, as the transmission / reception method of the RIP packet and its format, the method described in RFC1058 can be used.

The following is a specific description assuming that the routing table 100 is in the state shown in FIG.

Here, as the initial contents of the routing table 100, the first is [target network address = 130.1.1.0, first transfer destination candidate address = 1]
30.1.1.1, the number of hops of the first transfer destination candidate address = 1, the second transfer destination candidate address = none, the number of hops of the second transfer destination candidate address = none], and the second is [Destination network address = 130.1.2.0, first transfer destination candidate address = 130.1.1.1, hop number of first transfer destination candidate address = 2, second transfer destination candidate address = 130.1.1.2, the number of hops of the second transfer destination candidate address = 4], and the third is [target network address = 130.1.3.0, first transfer destination candidate address = 130. 1.1.1, number of hops of first transfer destination candidate address = 3, second transfer destination candidate address = 13
0.1.1.3, the number of hops of the second transfer destination candidate address = 5], and the fourth is [target network address =
130.1.4.0, first transfer destination candidate address = 13
0.1.1.1, number of hops of first transfer destination candidate address = 4, second transfer destination candidate address = 130.1.1.
4, the number of hops of the second transfer destination candidate address = 6].

First, as an example, as shown in FIG.
The packet structure is [target network address = 13
0.1.5.0, number of hops = 5, received address = 13
0.1.1.5], it is transferred from the selection means 512 to the first candidate comparison means 521. In such a case, the first candidate comparison unit 521 may use the routing table 1 shown in FIG.
00 [target network address = 130.1.5.
[0] is not present in the network address, the first candidate comparing unit 521 transfers the RIP packet to the routing table control unit 531 and the routing table control unit 531 adds the RIP packet to the routing table 100. As the fifth of the routing table 100, as shown in FIG. 6, [target network address = 130.1.5.0, first transfer destination candidate address = 130.1.1.5, first transfer destination candidate] Address hop count = 5, second transfer destination candidate address = none, second transfer destination candidate address hop number = none] is added.

Next, as another example, the structure of the RIP packet is as shown in FIG. 7 [target network address = 13
0.1.4.0, number of hops = 3, received address = 13
0.1.1.6], and is transferred from the selection unit 512 to the first candidate comparison unit 521. In this case, the first candidate comparison unit 521 uses the [target network address = 130.1.
As a first transfer destination candidate address to the network address of [4.0], [transfer destination address = 130.1.
1.1, the number of hops = 4] is the fourth information,
Since the received RIP packet has a smaller hop count, the RIP packet is transferred to the routing table control unit 531. Routing table control unit 5
Reference numeral 31 is for writing the already existing first transfer destination candidate address and its hop count to the second transfer destination candidate address and its hop count, and for writing the RIP packet to the first transfer destination candidate address and its hop count. , The fourth in the routing table 100 is [target network address = 130.1.4.0, first transfer destination candidate address = 130.1.1.6, first transfer destination candidate, as shown in FIG. Address hop count = 3, second transfer destination candidate address = 1
30.1.1.1, the number of hops of the second transfer destination candidate address = 4].

As another example, the structure of the RIP packet is as shown in FIG. 9 [target network address = 13
0.1.1.0, hop count = 2, received address = 13
0.1.1.3], and is transferred from the selection unit 512 to the first candidate comparison unit 521. In this case, the first candidate comparison unit 521 uses the [target network address = 130.1.
1.0] as the first transfer destination candidate address to the network address [transfer destination address = 130.1.
1.1, the number of hops = 1] is first, but
Since the hop count of the received RIP packet is larger, the RIP packet is transferred to the second candidate comparison means 522. The second candidate comparison unit 522 transfers the RIP packet to the routing table control unit 531 because the routing table 100 shown in FIG. 8 does not have the information on the second transfer destination candidate address. The routing table control unit 531 uses the RIP packet shown in FIG.
The destination candidate address and the number of hops thereof are written in the routing table 100 shown in FIG.
0.1.1.0, first transfer destination candidate address = 130.
1.1.1, number of hops of first transfer destination candidate address =
1, second transfer destination candidate address = 130.1.1.3,
The number of hops of the second transfer destination candidate address = 2].

As another example, the structure of the RIP packet is as shown in FIG.
130.1.3.0, hop count = 6, received address = 1
30.1.1.7], and is transferred from the selection unit 512 to the first candidate comparison unit 521. In this case, the first
The candidate comparison unit 521 displays the [target network address = 130.1.
3.0] as the first transfer destination candidate address for the network address [target network address = 1
30.1.3.0, first transfer destination candidate address = 13
0.1.1.1, number of hops of first transfer destination candidate address = 3, second transfer destination candidate address = 130.1.1.
3, the number of hops of the second transfer destination candidate address = 5] is third, so the number of hops of the first transfer destination candidate address and the number of hops of the RIP packet are compared, and the result is RIP. Since the number of hops of the packet for use is equal to or larger than the number of hops of the first candidate transfer destination address, the packet is transferred to the second candidate comparison unit 522. The second candidate comparison means 522 is the second
The hop count of the transfer destination candidate address and the hop count of the RIP packet are compared, and as a result, the hop count of the RIP packet is equal to or larger than the hop count of the second transfer destination candidate address, the RIP packet is discarded. Forwarded to means 532.

In this way, if the RIP packet communication is performed, even when the packet is transferred to the first transfer destination candidate address but cannot be transmitted, the routing table 100 is re-established.
Since it can be transferred to the second transfer destination candidate address with reference to, the routing can be continuously performed. That is, this routing table 100 is
The first transfer destination candidate address and its hop count as a part of the transfer destination candidate address due to the use of the second transfer destination candidate address and the second transfer destination candidate address and its hop count as the other part of the transfer destination candidate address, and The transfer destination candidate address and the number of hops thereof are selected based on the presence or absence of the first transfer destination candidate address, the number of hops of the RIP packet, and the result of comparing the size of the number of hops of the corresponding portion of the table. , The second transfer destination candidate address and its hop count are selected based on the result of comparing the presence or absence of the second transfer destination candidate address, the hop count of the RIP packet, and the hop count of the corresponding portion of the table. Becomes

[0034]

As described above, according to the present invention, the presence / absence of the first transfer destination candidate address and the RIP are determined by the determination unit.
Of the number of hops of the packet for transmission and the number of hops of the table corresponding part, the presence / absence of the second transfer destination candidate address, and R
The hop count of the IP packet and the hop count of the corresponding portion of the table are compared with each other, and the routing table has a first transfer destination candidate address and its hop count, and a second transfer destination candidate address and its hop count. I am creating it. By referring to this routing table, it becomes possible to refer to the routing table again and transfer to the second transfer destination candidate address even when the transfer is not possible although the transfer is made to the first transfer destination candidate address. Therefore, the routing can be continuously performed without restarting the transfer after newly creating the routing table.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a routing table creation device according to an embodiment to which a routing table creation method of the present invention is applied.

FIG. 2 is a flowchart showing an operation process of a routing table creation method by the routing table creation device shown in FIG.

3 shows a configuration of a routing table provided in the routing table creation device shown in FIG.

FIG. 4 shows one state of the routing table described in FIG.

5 is a diagram showing an example of the configuration of a RIP packet received by the routing table creation device shown in FIG.

FIG. 6 shows another state of the routing table described in FIG.

FIG. 7 shows another example of the configuration of the RIP packet described in FIG.

FIG. 8 shows another state of the routing table described in FIG.

9 illustrates another example of the configuration of the RIP packet described in FIG.

FIG. 10 shows another state of the routing table described in FIG.

11 shows another example of the configuration of the RIP packet described in FIG.

FIG. 12 is a block diagram showing a basic configuration of a conventional routing table creation device.

13 is a flowchart showing an operation process of a routing table creation method by the routing table creation device shown in FIG.

14 is a diagram showing a configuration example of a RIP packet received by the routing table creation device shown in FIG.

FIG. 15 shows the contents of a routing table provided in the routing table creation device shown in FIG.

[Explanation of symbols]

 1,51 receiving unit 2,52 determining unit 3,53 control unit 4,54 transmitting unit 10,100 routing table 11,511 receiving unit 12,512 selecting unit 21 comparing unit 31,531 routing table control unit 32,532 discarding unit 41,541 Reference means 42,542 Transmission means 301 Network address 302,403,703,705 Hop number 303 Reception address 401,701 Target network address 402 Transfer destination candidate address 521 First candidate comparison means 522 Second candidate comparison means 702 Second 1 transfer destination candidate address 704 2nd transfer destination candidate address

Claims (3)

[Claims] 1. A first transfer destination candidate address as a part of a transfer destination candidate address by using a routing information protocol, a hop number of the first transfer destination candidate address, and other parts of the transfer destination candidate address. A routing table having a second transfer destination candidate address and a hop number of the second transfer destination candidate address, wherein the first transfer destination candidate address and the hop number of the first transfer destination candidate address are: The second transfer destination is selected based on the presence / absence of the first transfer destination candidate address, the hop count of the routing information protocol packet, and the result of comparing the hop count of the corresponding portion of the table. The destination candidate address and the number of hops of the second transfer destination candidate address are determined by the presence / absence of the second transfer destination candidate address and the route. A routing table selected based on the number of hops of a packet for a routing information protocol and the result of comparing the number of hops of the corresponding portion of the table. 2. A method of creating a routing table using a transfer destination candidate address and the number of hops of the transfer destination candidate address by using a routing information protocol, wherein a first part is included as a part of the transfer destination candidate address. The first transfer destination candidate address and the first transfer destination candidate address based on the result of comparing the presence or absence of the transfer destination candidate address, the hop count of the routing information protocol packet, and the hop count of the corresponding portion of the table.
First candidate selection step of selecting the number of hops of the transfer destination candidate address, and second as the other part of the transfer destination candidate address.
Second transfer destination address and the second transfer destination based on the result of comparison between the presence or absence of the transfer destination candidate address of the packet, the number of hops of the routing information protocol packet, and the number of hops of the corresponding portion of the table. And a second candidate selection step of selecting the number of hops of the candidate address. 3. A routing including a routing table having a transfer destination candidate address and the number of hops of the transfer destination candidate address by using a routing information protocol, and a determination unit for determining the transfer destination candidate address and the hop number. In the table creation device, the determination unit compares the presence / absence of a first transfer destination candidate address as a part of the transfer destination candidate address, the number of hops of a packet for routing information protocol, and the size of the number of hops of a corresponding part of the table. A first candidate comparing means for selecting the first transfer destination candidate address and the number of hops of the first transfer destination candidate address based on the result, a first candidate selection step, and the transfer destination candidate address. As another part, the presence / absence of the second transfer destination candidate address and the routing information Second selection of the second transfer destination candidate address and the hop count of the second transfer destination candidate address based on the comparison result of the hop count of the packet for the communication protocol and the hop count of the corresponding portion of the table.
And a candidate comparison means, wherein the routing table is
A routing having the first transfer destination candidate address and the number of hops of the first transfer destination candidate address, and the second transfer destination candidate address and the number of hops of the second transfer destination candidate address. Table making device.