Quote:
Originally Posted by Chrysalis
Ignition I dont understand you at times, I know you know its wrong because not too long ago you yourself was moaning about VM's peering situation. But then randomly you will comne out and fight their corner. It looks clear fowhatever reason VM have weighted the US nlayer link a higher priority than both abovenet and ams-ix, as to why we dont know. Likely financial tho.
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Both links use nLayer. Both routes are going to the same IP address 199.27.135.74, neither is being preferred.
The AS Path to that destination is the same length on both, so the routing decision comes down to which route internally within the VM network to get to the transit is the best option, which will vary depending where on the network you are and your proximity to the two links in question.
popl-bb-1a has the following paths to get to nlayer, which is, actually, all the VM network cares about in this case:
popl-tmr-1
amst-ic-1
ams-ix.ae1.cr1.ams2.nl.nlayer.net
popl-bb-1b
popl-tmr-2
tele-ic-2
eqix.xe-3-3-0.cr2.iad1.us.nlayer.net
Each hop will have an IS-IS cost, it chooses the shortest path - Amsterdam.
popl-bb-1b has the following options:
popl-tmr-2
tele-ic-2
eqix.xe-3-3-0.cr2.iad1.us.nlayer.net
popl-bb-1a
popl-tmr-1
amst-ic-1
ams-ix.ae1.cr1.ams2.nl.nlayer.net
Again - per the routing protocol it chooses the shortest path - Equinix.
This is not some manual tuning to avoid costs. I'm sticking up for VM on this because you are wrong with your accusations of manual routing for cost purposes (in this case).
---------- Post added at 23:25 ---------- Previous post was at 23:19 ----------
Quote:
Originally Posted by Chrysalis
BGP works how its configured you know that, each route is applied weighting to work to the isp's preference.
Sorry I missed the anycast part, however this begs the question still how this issue is not affecting other isp's. If we remove all the jitter from pip's trace his is clearly closer so should be a favourable destination for anycast.
How do you know both paths are configured with equal priority?
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Anycast doesn't work like that, it doesn't measure latency, decisions are made by BGP and whatever IGPs the ISPs are using. I have no idea at all of the relevance of latency in pip's case, EIGRP is the only routing protocol that comes to mind that uses latency in routing decisions, VM use an IP/IS-IS/MPBGP network. He goes to Amsterdam because his route towards nlayer goes via popl-bb-1a, so the lowest metric route internally is via Amsterdam rather than going via popl-bb-1b to go via Equinix.
Perhaps VM are the only operator who peer with nlayer in multiple places?