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List:       ms-ospf
Subject:    
From:       SUBSCRIBE OSPF Anonymous <gsaravanan () ZIGMA ! COM>
Date:       2002-08-16 15:11:15
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Hi,

Before I start my question, my Thanks to all, who did listen to my earlier question \
and trying to get back to me with ideas! I really appreciate all your time and \
effort.

Well, I have one more question when OSPF establish adjacency with its neighbors.

During that period, I try to act my Simulator as Master and let OSPF Route be slave \
and while trying to establish an adjacency with OSPF Router, I am trying to send the \
below mentioned packet during DD packet exchange.

But, for some reason, OSPF router could not form an adjacency when I send these \
packets and stops at exChange state

i.e. OSPF Router and Simulator understands Master Slave relationship
OSPF Router sends DD packet with master sequence number and also sends LSA Header for \
(routerLSA)


I have few questions and any suggestions from your end is welcome and will be a big \
relief.

        * While looking at the packets, I am not sure how to calculate the checksum \
for LSA Header. I was under the impression that I should exclude Link State Age while \
                performing checksum, but still not sure what I am missing here ...
        * Even though, LSA Header only contains 20 bytes, I noticed we always try to \
                specify Packet Length has 36 bytes. Any reasons!?
        * Also, when I monitor my network, I notice for the packets only information \
upto Data Description and don't see LSA Header info.

Thanks and have a wonderful evening!

- G

Data Description Packet Information:


// ----- OSPF DD Ack Packet -----
//


//
// ----- Ethernet II -----
//

define ospf [ 00 20 9c 23 bc 70
        08 00 20 ac 9d d5
        08 00

//
// ----- Internet Protocol -----
// ----- 20 bytes -----

45
00
00 34                     // Total Length
5a a0                     // Identification
00                        // Flags
00                        // Frame Offset
40                        // TTL
59                        // Protocol (OSPF)
00 00                     // Checksum
0a 65 01 43               // Source
0a 65 01 41               // Destination

//
// ----- OSPF Header -----
//

02                        // OSPF Version
02                        // OSPF Packet Type (Hello Pkt)
00 34                     // Packet Length
0a 65 01 43                // Source OSPF Router ID
0a 65 01 40                        // Area ID
00 00                     // Packet Checksum
00 00                     // Auth Type (None)
00 00 00 00               // Auth Date (None)
00 00 00 00

//
// ----- OSPF Data Description Info -----
//

05 dc                     // Interface MTU
02                        // OSPF Version
00                        // Master
00 00 00 02              // DD Sequence


//
// ----- OSPF DD w/ LSA Header -------- 64 BYTES
//
01 88                   // LS Age 392 seconds
02                              // Options
01                              // Router LSA
0a 65 01 43             // Link State ID
0a 65 01 43             // Adv. Router
00 00 01 00             // LS Sequence Number
0a 02                   // Checksum
00 24                   // Length
];

xsum ospf[24] 14 20;
xsum ospf[46] 34 52;
// -xsum ospf[82] 66 28; - Checksum for LSA Header

send ospf;


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