Limitation on stubnet prefixes

[Ondrej Zajicek]

On Fri, Jul 26, 2019 at 10:49:31AM +0200, Andre Cunha wrote:
> Hello, 
> 
> Is there a limit on the number of stubnet prefixes that we can configure?  I have configured 50000 stubnets but my router receives only 1084 routes. 

Hello

Yes, stubnet prefixes are announced as a part of the Router-LSA, with
12 B per prefix. With 16bit Router-LSA length, the limit is about 5400
Router-LSA entries (including other entries than just stubnets). But note
that having such large Router-LSA may cause many problems, including OSPF
packet fragmentation, so i would generally suggest to not have larger
Router-LSA than MTU, i.e. not more than ~100 entries.

This length limit is not enforced in BIRD, if you configure more
stubnets, the Router-LSA with length modulo 64k is generated, which
may be invalid. I should add some check and warning there.

External routers are announced as separate External-LSAs, so there is no
such limit for them.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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