While verifying things about the anycast recdns setup, I was reminded that it's still doing Layer4 hashing at the router, which means as a single client host varies its source port, it gets different server hosts. For this and all foreseeable future uses of router-side ECMP, I think we'd rather be hashing on just Layer3 so that the mapping is consistent for a given client machine even as its client port number changes.
Description
Description
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Resolved | BBlack | T104442 Investigate better DNS cache/lookup solutions | |||
| Resolved | ayounsi | T186550 Anycast recdns | |||
| Resolved | ayounsi | T228190 Roll out Anycast RecDNS to more servers | |||
| Resolved | ayounsi | T230955 Configure Layer3 hashing for router ECMP (for anycast DNS) |
Event Timeline
Comment Actions
Tested in ulsfo with:
# show forwarding-options enhanced-hash-key
family inet {
no-destination-port;
no-source-port;
}
family inet6 {
no-destination-port;
no-source-port;
}Older routers might need instead:
# show forwarding-options hash-key
family inet {
layer-3;
}Comment Actions
Mentioned in SAL (#wikimedia-operations) [2019-08-22T00:19:11Z] <XioNoX> push L3 ECMP to codfw routers - T230955
Comment Actions
Mentioned in SAL (#wikimedia-operations) [2019-08-22T00:22:02Z] <XioNoX> push L3 ECMP to eqsin routers - T230955
Comment Actions
Mentioned in SAL (#wikimedia-operations) [2019-08-22T00:23:34Z] <XioNoX> push L3 ECMP to esams routers - T230955
Comment Actions
Mentioned in SAL (#wikimedia-operations) [2019-08-22T00:27:26Z] <XioNoX> push L3 ECMP to eqiad routers - T230955