Cisco OSPFv2 auth crypto sequence number

[oaschepkov]

Hello, I'm faced with the fact that the Cisco router sends "LS update" and "Hello" packets with the same sequence number in the  OSPFv2 header if "Hello" and "LS" are sent at the same time. Is this a correct behavior?

[oaschepkov]

I have carefully studied the RFC 2338 and found the following paragraph:

D.4.3 Generating Cryptographic authentication
    ...
(5) The 32-bit Cryptographic sequence number (see Figure 18)
    is set to a non-decreasing value (i.e., a value at least
    as large as the last value sent out the interface). The
    precise values to use in the cryptographic sequence
    number field are implementation-specific. For example,
    it may be based on a simple counter, or be based on the
    system's clock.

So this behavior is acceptable.