Help: Upstream says my prefix is 'too long' for their filters

Upstream at HostHatch just rejected my /24 with "prefix length exceeds maximum allowed" and I need this routed by Friday for a client migration. Not my first rodeo but first time hitting this specific error.

Troubleshooting so far:

• Confirmed prefix is clean on all major RBLs
• IRR route objects created and matching
• RPKI ROA valid
• Upstream says their side shows "received prefix too long" in logs

Their gear is old Cisco, probably ISR gen 1 or early ASR. I remember this default from a CloudCone migration two years ago.

pro tip: old IOS defaults to max prefix length /23 for received routes unless explicitly configured

heads up: this is more common at budget upstreams running code from 2012-2015

Has anyone else hit this recently? I need the exact config fix to send them.

Already face this problem last year with my upstream at GreenCloudVPS

They using old IOS also and the engineer not know about this setting

I ask them can or not change the prefix limit and they say must check with senior

Two days later they come back with config already

The fix is ip prefix-list something something but I forget already lah

You can ask them check their bgp neighbor config for prefix filter dong

I hit this with Time4VPS upstream before — https://www.time4vps.com

They running IOS 15.1 and default maximum prefix is /23 /23

The fix is simple

Neighbor x.x.x.x prefix-list FILTERNAME in

But you must change the prefix list to permit 24 or shorter

IP prefix-list FILTERNAME seq 5 permit 0.0.0.0/0 le 24

Thank you for sharing this thread