Question about graceful restart timer

[Ondrej Zajicek]

On Thu, Aug 25, 2016 at 08:23:09AM +0200, Robert Wein wrote:
> Hello bird users,
> 
> one of our VIX customers (RS-Client) came up with a question about the graceful restart timer.
> At his Cisco he found:
> 
> ------------
>  Graceful Restart Capability: advertised and received
>       Remote Restart timer is 0 seconds
> ------------
> 
> We don't have anything related to graceful restart in our config, defaults should apply.
> 
> As far as I understand the default for graceful restart ("aware") should be enough to advertise capability and timer.

Restart timer specifies how long should peers wait for the BGP speaker to
restart, therefore it makes sense only in full graceful restart mode.
In receive-only mode ('aware') we always send zero. See RFC 4724:

   When a sender of this capability does not include any <AFI, SAFI> in
   the capability, it means that the sender is not capable of preserving
   its forwarding state during BGP restart, but supports procedures for
   the Receiving Speaker (as defined in Section 4.2 of this document).
   In that case, the value of the "Restart Time" field advertised by the
   sender is irrelevant.

-- 
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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