Hi Mike,
> On Feb 28, 2024, at 11:59, Mike Fox <mj...@us.ibm.com> wrote:
>
> Section 21.4.2 of RFC 2328 has a couple of seemingly contradictory statements
> I am trying to reconcile.
>
> It says that a network LSA is only originated by the DR if the DR is fully
> adjacent to at least one other router, and it includes itself in the list of
> fully adjacent routers.
>
> But it also says that if a router is no longer the DR, it flushes the network
> LSA by setting it to MAXAGE and flooding it. However, in this case the
> router may not be fully adjacent to any other routers.
Section 14.1 of RFC 2328 is clear. You don’t need to re-originate the LSA, you
simply set the LS age to MAXAGE and reflood it. So, you wouldn’t modify the
sequence number, LS checksum, or contents including the list of adjacent
neighbors.
An LSA can be flushed from the routing domain by setting its LS
age to MaxAge, while leaving its LS sequence number alone, and
then reflooding the LSA. This procedure follows the same course
as flushing an LSA whose LS age has naturally reached the value
MaxAge (see Section 14). In particular, the MaxAge LSA is
removed from the router's link state database as soon as a) it
is no longer contained on any neighbor Link state retransmission
lists and b) none of the router's neighbors are in states
Exchange or Loading. We call the setting of an LSA's LS age to
MaxAge "premature aging".
Hope this helps,
Acee
>
> The question that arises is: should the router still include itself in the
> list of attached routers when it’s flushing a network LSA because it’s no
> longer DR, and it isn’t fully adjacent to any other routers? My product has
> been sending an empty attached routers list in this case, and recently
> Wireshark has started flagging that as an error, saying the network LSA is
> four bytes below the minimum size.
>
> Mike Fox
> z/OS Communications Server
> <https://www.ibm.com/products/zos-communications-server>
> IBM Enterprise Networking Solutions
> Research Triangle Park, NC USA
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