Use bgp_aigp instead of bgp_med to select the optimal route based on delay

[Ondrej Zajicek]

On Mon, Oct 09, 2023 at 11:29:33PM +0800, Brandon Zhi wrote:
> Hi all,
> 
> I plan to use bgp_aigp instead of bgp_med to find the optimal route based
> on incremental pings per node. For example, if the delay between one node
> and another node is 40, then bgp_aigp increases by 40 after passing this
> ibgp.
> 
> void bgp_aigp [O]
> This attribute contains accumulated IGP metric, which is a total
> distance to the destination through multiple autonomous systems.
> Currently, the attribute is not accessible from filters.
> 
> But it seems I can't modify this value?

Hi

You cannot modify bgp_aigp - total distance, but you can modify per-hop
distance, which is added to it automatically in each (inter-AS) step.

It is either regular IGP metric (e.g. the attribute 'ospf_metric1' in
case of OSPF), or manually configured one (the attribute 'igp_metric'),
or configured cost of inter-AS link [0].

[0] https://bird.network.cz/?get_doc&v=20&f=bird-6.html#bgp-cost

I think that using bgp_aigp is the right tool for your use case, but
details depend on specific topology of your confederation - whether each
internal AS in the confederation is nontrivial network with IGP, flat
network, or just one router.

-- 
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."