Visitor
•
3 Messages
DHCPv6-PD /60 delegated but return traffic not routed back.
I’ve tried in-app chat and phone support with no success.
Setup
Hitron CODA56 modem
Xfinity is correctly issuing a DHCPv6-PD /60.
Delegated prefix
[Edited: "Personal Information"]::/60
WAN IPv6
[Edited: "Personal Information"]/128
Symptoms
Packets sourced from the delegated prefix leave my WAN interface (confirmed via tcpdump), but no replies return. WAN-sourced IPv6 traffic (from the /128) works perfectly to the same destinations.
I’ve ruled out local configuration issues through power cycles, IPv6 resets, and verification that forwarding is enabled.
I’m requesting escalation to network engineering / CMTS team to check:
- DHCPv6-PD provisioning and the residential /60 boot file for the modem
- CMTS routing tables for prefix [Edited: "Personal Information"]/60
- Return path / IPv6 forwarding for the delegated prefix
This is not a local config or modem problem. The prefix is being issued but return traffic for it is not being routed back to my connection.
user_fwd75x
Visitor
•
3 Messages
21 hours ago
Additional detail
WAN-source IPv6 works:
[Edited: "Personal Information"]
But delegated-prefix-source traffic fails:
[Edited: "Personal Information"]
Packet capture on my router’s WAN interface shows the packets leaving toward Comcast:
[Edited: "Personal Information"]
No replies return.
I also fully power-cycled the Xfinity modem and router, disabled/re-enabled IPv6 on WAN and LAN, and reacquired the same delegated prefix. The issue persists.
(edited)
0
0
zandor60657
Contributor
•
233 Messages
20 hours ago
What are you using for a router? What are you trying to do with a /60? That gets you 16 subnets. I've been using 5 IPv6 subnets on Comcast for years. 2 for my computers (wifi vs. wired - wifi is more restricted), 1 for gizmos, streaming sticks, IoT, phones, etc., 1 for a guest network, and 1 for my work gear since I work from home part time. Works just fine, though I did have to modify a firewall rule to get the DHCP6 response. My Mikrotik router had a default rule that expected a DHCP response from the same subnet, but Comcast was sending from another subnet. You're apparently getting the DHCP6 response, so that's not it.
0
0
user_fwd75x
Visitor
•
3 Messages
2 hours ago
Hey @zandor60657 thanks for the response.
The router is a Firewalla Gold behind the Hitron CODA56 modem.
I have to admit I don't fully understand IPv6 yet. I thought it was similar to IPv4, where the WAN device hands off all the settings.
On the network I have a Trusted lan and an IoT vlan30.
Are you saying the router has some control over the situation?
Here is what I see on my router.
[Image Removed: "Personal Information - IP Addresses"]
(edited)
0
0